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Thread: Cooling System Bleeding

  1. #1
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    Cooling System Bleeding

    *Edited 7/31/11 to include TIS references and consolidate information from with the discussion.

    Here is a complete DIY for Bleeding the E39 cooling system using the proper BMW/Bentley Procedure. This procedure is based on the following BMW TIS documents

    TIS 17 00 Instructions for working on cooling system
    http://tis.spaghetticoder.org/s/view.pl?1/04/35/64

    TIS 17 00 005 Draining and topping up coolant
    http://tis.spaghetticoder.org/s/view.pl?1/02/26/14

    TIS 17 00 039 Bleeding cooling system and checking for leaks
    http://tis.spaghetticoder.org/s/view.pl?1/01/34/82

    The V8 bleeding procedure is essentially identical except that there is no Thermostat cover bleeder screw, all bleeding is done at the expansion tank bleeder screw.

    A number if Forum members with minimal auto repair experience have used this procedure succesfully on the first try to bleed their cooling systems after multiple attempts using other procedures, hopefully they will choose to share their experiences using this very simple and straightforward procedure.

    Please take a few moments to provide any comments on this procedure or to share your experiences using it, Thanks.


    First a couple of general notes;

    - If you have removed the Water pump then you will need about 1.0 to 1.25 gallons of mixed coolant to refill and bleed the system

    - If you have removed the Water pump AND the Lower radiator hose then you will need about 1.5 to 1.75 gallons of mixed coolant to refill and bleed the system

    - If you have changed the thermostat you will need about .5 to .75 gallons of mixed coolant to refill and bleed the system

    - There is no need to drill a hole in your new thermostat, see video and photos below showing the bleed hole in the thermostat cover.

    - Never open a bleeder screw or the expansion tank when the engine is hot, this is the same as having a crack in your radiator and does not aid in the proper bleeding of the system

    - Take care when tightening the bleeder screws as the OEM screws are plastic and can be stripped or damaged easily.

    - Jacking or inclining the front of the car 6 inches or more will speed up the process but is not required.

    - Be sure to use a 50/50 mix of BMW coolant and distilled water(available at Walmart) All references to coolant in this procedure refer to a 50/50 mix.

    - Various discussions on the efficacy of running the engine to complete the bleeding of the system have presented a lot of confusing information. Certain equipment configurations may require that the engine be run to purge air from the heater core, however there is no evidence that the engine needs to be hot or even warm to do this. Simply running the engine for a minute or two after completing the static bleed procedure presented here is all that is required and this is covered during the drive and cool portion of this procedure and should not normally need to be done as a separate step. This may be equivalent to what others have called a warm bleed procedure however I do not know if that is what they are referring to at this point. There is no reason, value or technical justification in opening the bleeder screws when the engine is at normal operating temperature while there exist a number of potential issues in doing so. There are no recommendations to do so in any BMW publication or any other reputable professional source thus I do not condone or recommend that this ever be done as this is essentially creating a controlled failure of the cooling system allowing boiling of the coolant in the engine which at best causes potential for air to be drawn back into the system and at worst could lead to damage equivalent to that which occurs from a component failure within the system. It should be noted also that this is expressly covered in BMW TIS 17 00 ;

    "Important!
    Open cooling system only when it has cooled down.
    Opening the cooling system while hot can result in air entering the system.
    This can cause overheating with permanent damage to the engine. "

    - Contrary to information presented in some other procedures and in this thread the bleeder screws in the thermostat cover and in the expansion tank ARE NOT at the same elevation. The Expansion tank screw is 1 to 2 inches higher than the thermostat cover screw as can be seen clearly in the photos below.


    - See end notes for information on Bleeder hole in thermostat housing bleeder screw elevations and aluminum thermostat cover.


    Written Procedure;


    1) With car cold turn on key to run position(do not start the car), set HVAC system to 90 degrees and fan on low.

    2) Remove coolant pressure cap on expansion tank and the bleeder screws from thermostat cover and expansion tank.

    3) Begin to pour coolant into expansion tank keeping level near top of tank until air free coolant flows from thermostat cover bleeder hole, install screw and close bleeder.

    4) Continue to fill expansion tank until air free coolant flows from the bleeder screw on the expansion tank, you will need to keep the expansion tank filled to top to complete this step. When no more bubbles then install and close the bleeder.

    5) Fill coolant in expansion tank to near top of tank then install the filler cap.

    6) Now take the car for a drive and get it warmed up to temperature, at least a 10 min drive, try to get some higher RPM driving in as well(like a short section of open road)

    7) Park car and let cool to ambient temperature(at least a couple of hours) then check the level of coolant in the expansion tank. If it is empty then repeat the bleeding process above, if after a repeat it is still empty then you have a bigger issue such as a leak or a damaged head gasket. If the level is low then top up to the full cold level indicated on the tank or slightly above.

    8) Monitor coolant level for several drive cycles adding coolant as needed to maintain the full cold level, coolant level should stabilize in one or two drive cycles.


    Video of Procedure:

    Note, this was filmed following a water pump and Radiator hose installation so about 1 gallon of coolant mix had been added prior to starting the recording, the procedure is identical regardless of amount of coolant that is required to be added.

    [ame]http://www.youtube.com/watch?v=Q6BeQozdOYc[/ame]

    [ame]http://www.youtube.com/watch?v=RMkCmJ3tPkQ[/ame]


    End Notes:


    Thermostat design and function
    (or why the system cannot become air locked even though certain people are for some reason convinced it can)

    air cannot get trapped in the block as the area behind the thermostat is directly connected through an open passage to the upper radiator hose. the main exit for the coolant flow passes behind the thermostat and into the upper radiator hose passage with no restriction whatsoever. The air cant get trapped back there it will escape into the radiator(past the thermostat cover bleed screw on its way.



    Additional thoughts on system design by benemorious

    If you guys don't mind an outsider (m50 e36) getting involved (and bumping a thread, no less) I have some things to say on the matter. Us e36 guys are also struggling with the myth of a difficult to bleed cooling system. For what it's worth, I've studied my cooling system (it looks just like yours(well, the parts relevant to air lock at least)) in great detail and after reading this thread I must say I do agree with NNY528I. Our observations and the conclusions we drew from them appear to be congruent. Never mind what any expert mechanic has to say, direct observations are always preferable.

    What is disputed is whether air can become trapped inside the block/head ("behind the thermostat"). The correct response to such a inquiry is repeated many times in this thread in many different ways. Air in the block/head cannot become trapped anywhere because there is no thermostat or anything else to prevent it from flowing freely out the top radiator hose and relieving itself via the bleeder screw or expansion tank.

    The key points to catch are that the cooling system features a thermostat located at the bottom radiator hose rather than the conventional top hose location, and that air inside the block is therefore allowed to flow freely out the top radiator hose, unobstructed by the thermostat as in other (air-lock prone) designs. If you don't wish to read any further, you don't have to. That information is sufficient to settle the dispute if you accept it. It has been stated over and over many times, but either overlooked or ignored outright in every case.

    Quote:
    *******> ********> Originally Posted by cnn
    For those who wonder about the coolant passages of an M52 engine...

    As I already mentioned in this cooling overhaul for my 1998 528i:
    http://www.bimmerboard.com/forums/posts/199986

    -------
    I recently changed my Tstat seals and for my curiosity, decided to probe the coolant passages using electrical wire and my finger!
    I confirmed the coolant flow as follows:
    - The WP circulates fluid from solid orange line from engine and solid blue line from UPPER Radiator Hose ---> dotted blue line (behind the thermostat) into the WP itself. This brings cool fluid into engine.
    - Then hot coolant builds up in the engine block and comes out in the dotted purple line ---> solid purple line into the upper rad hose.

    - There is no direct connection between #1 (blue) and #2 (purple) areas.
    - So air trap behind the tstat is a distinct possibility in the M52 engine.

    Just some tidbit about the M52 engine for those with curious mind...



    There is an oversight here which makes all the difference. It has been stated already, but I will attempt to restate it with more verbosity.

    While there is no direct connection between blue and purple, there IS a direct connection inside the head between the ORANGE hole and the PURPLE hole. They are effectively the same hole. They both contain hot water from the head ready to be either recirculated directly when the engine is cold (the closed dual-action thermostat prevents water from passing from the blue line to the dotted blue line, while permitting water to pass from orange to dotted blue) or cooled by the radiator first and then recirculated if the engine is hot (the open thermostat blocks water from going from orange to dotted blue while allowing it to go from blue to dotted blue - water from orange can then only come out purple.) There is no difference between saying "air trapped in the block/head" and "air trapped behind the thermostat" and "air trapped in the orange/purple area." The area behind the thermostat is the orange/purple area, and the orange/purple area is the top opening to the coolant passages of the head and therefore block.

    Here's the significance of that:

    Because of the connection between the orange hole (from head/block passages) and the purple hole (output to radiator/bleed screw) it is not possible for air to become trapped inside the block/head AKA behind the thermostat since it is not stopped by the thermostat and can come freely out the purple hole. To support the theory that the engine can become air locked, the assumption is made that air in the head/block has no escape route other than the orange hole behind the thermostat. This is not the case. Rather, the air is also free to come out the purple hole, and this is what it does.

    BMW has chosen to remove the thermostat from the airlock-prone top hose position and place it in the airlock-free bottom hose position. A very wise move, for even while filling a completely dry block, all the air is guaranteed to come out the top radiator hose and be released via the expansion tank or bleeder screw.


    Aluminum Thermostat Housing,

    Made by URO, purchased through Pelican for about $12

    Unit is decently made and includes a gasket and metal bleeder screw, however there was some casting issues including some flash and a heavy shoulder in the upper radiator hose port that needed to be dremeled out of the housing.

    Installed

    Bleeder hole




    Bleeder Screw elevation comparison


    Side of car body showing car is sitting level with ground.


    Note engine is inclined in the car

    Thermostat cover bleeder screw at 5 inches



    Expansion tank bleeder screw at about 4 inches even though the reference level slopes upward towards the radiator thus if they were at the same level a measurement of at least 5.5 to 6 inches would be indicated however clearly the expansion tank is higher than the thermostat cover.



    Last edited by NNY528I; 07-31-2011 at 03:07 PM.
    >'97 528i, 200000 miles, Hella Xenons, 17" Stilauto wheels, Vogtland Drop Springs, Dynomax Race Muffler, Homelink, 540 brake upgrade, 15mm spacers >'65 & '74 MG Midgets BFC OT Lego Club #48 Manual conversion in process!!!



  2. #2
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    Nicely done Jason!
    I'll leave this in E39 main until you get some feedback.

  3. #3
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    Nice write up. My experience, it helps if the car front is on a ramp during the fill. I also warm up the car and bleed the system before driving out on the road. Keep a flat head screw driver handy just in case you need to bleed the system while on the road.

  4. #4
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    I always wanted to put new coolant in my M5 but I'm in fear of screwing something up...

  5. #5
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    Quote Originally Posted by Kevin Da Clean1 View Post
    I always wanted to put new coolant in my M5 but I'm in fear of screwing something up...
    Just follow the above and you cant screw it up. It really isnt that hard. I did more or less what Jason did with the exception after I stopped getting air out I drove it around the block and then bled more to make sure no more air was in the system. I drive a little over 100 miles round trip to work and didnt want any surprises. But that really isnt necessary.

    Good write up. Venting hot coolant and steam isnt really a good idea and can be as has been pointed out counter productive to successful bleeding of the system.

  6. #6
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    Nice write-up.
    So is that casting issue why some people a few years back reported not to use the aluminum thermostat housing (due to leaks)?

    Thanks
    Looking for a DIY? Parts? Check this out, it might be your ticket

    Stable: e92is, e53 N62, e46M54B25, Tribby & e39 M54B30 R.I.P.

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    Quote Originally Posted by Doru View Post
    Nice write-up.
    So is that casting issue why some people a few years back reported not to use the aluminum thermostat housing (due to leaks)?

    Thanks
    Not that I can tell, the casting seems flush to the block and well machined its more about excess metal in places in the coolant passages. It has not leaked that I can see but it has only been a couple of days.

    Quote Originally Posted by peterv View Post
    ...... I also warm up the car and bleed the system before driving out on the road. Keep a flat head screw driver handy just in case you need to bleed the system while on the road.
    You should never ever have to do this. This is what has really confused and messed up a lot of people. The car will self bleed the last little bits of air into the expansion tank which is why the excess was left in the tank at the end.

    NEVER OPEN A HOT COOLING SYSTEM, you are just asking for trouble.

    Quote Originally Posted by bmw chris View Post
    Just follow the above and you cant screw it up. It really isnt that hard. I did more or less what Jason did with the exception after I stopped getting air out I drove it around the block and then bled more to make sure no more air was in the system. I drive a little over 100 miles round trip to work and didnt want any surprises. But that really isnt necessary.

    Good write up. Venting hot coolant and steam isnt really a good idea and can be as has been pointed out counter productive to successful bleeding of the system.
    The drive and cool cycle will remove any excess air from the system, no need to rebleed the cooling system.
    Last edited by NNY528I; 03-23-2010 at 06:17 AM. Reason: Automerged Doublepost
    >'97 528i, 200000 miles, Hella Xenons, 17" Stilauto wheels, Vogtland Drop Springs, Dynomax Race Muffler, Homelink, 540 brake upgrade, 15mm spacers >'65 & '74 MG Midgets BFC OT Lego Club #48 Manual conversion in process!!!



  8. #8
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    Nice writeup! Thanx!

  9. #9
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    Great info guys. Now I can change the coolant in my M5 myself & not have the fear of getting air trapped in the system... !

  10. #10
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    Excellent DIY.

    Many people on bimmerfest follow the book (Bentley) and the above procedures and still have problem purging air out of the system. It is kind of hit-and-miss issue, some succeed and some don't succeed in bleeding cooling system using this procedure. I have a few suggestions:

    1. Take a minute to study the design of the E39 cooling system (see figure below). When the car is cold in the morning and you start the engine: during the warm-up phase, there is some hot coolant getting into the driver's side hose, "ready" to go through the radiator once the thermostat is open. Think about the thermostat as the "flood gate".

    2. Now once the thermostat is open, the flow direction is:
    Engine ---> driver's side hose ---> upper radiator ---> across radiator (to be cooled down)---> lower radiator hose ---> through thermostat area to cool engine.

    - So in a normal engine at operating temp, the lower hose is considered the "Cold" side because the coolant has been cooled by the radiator but it is still somewhat "Hot" to the human hand anyway (maybe around 60-70 deg C, enough to burn your skin!). Here is the direction of coolant flow (from M54 but M52 flow is the same):



    3. The bleed hole in the thermostat housing allows only air trapped inside the tstat housing to get out. But if you have the real "air lock" problem, which is the air pocket trapped behind the thermostat, that bleeder hole tstat housing will not allow the air lock to get out. This is a common problem and many people scratch their head bleeding the cooling system. If you study the diagram above, you will see that once an air lock develops, the thermostat cannot open properly because it is not submerged in coolant (it needs to be submerged in hot coolant to open at let's say 88-92C range).

    To get rid of air lock behind the thermostat, you can either:

    a. Rely on the tstat design, which has an arrow that should point straight up. I assume Behr or Wahler designs the arrow with a tiny air passage at the arrow (I could not detect the air passage with my own eyes).

    b. Or drill a small hole in the thermostat. Some may disagree with this trick but this trick (drill a small hole in the thermostat) has been around for a while and is well-known to many BMW, Porsche indys for a long time:
    http://www.bmwe34.net/E34main/Maintenance/Engine/Coolant%20replacement.htm

    So, drilling a hole in the tstat is an option and this is my personal preference. I drilled a hole in my tstat and 4 years later not a single problem.
    Just Google Images "drilling hole thermostat", and you will see hundreds of pictures illustrating this trick.

    In fact, many Volvo, VW etc. (made by Wahler or Behr) thermostats come from the factory with a hole pre-drilled anyway to prevent air lock.

    4. Bleeding with engine hot or cold is subject to debate. Some do it cold and some do it hot.
    Again, do a google search on this topic and you will see 2 different schools of thoughts.

    - If engine is hot, you can shut it off and wait a bit (maybe 10-15 min). Wear rubber gloves to prevent burn.
    I agree with NNY528i that you should not remove the reservoir cap completely when engine is hot, b/c there is a risk of coolant gushing out.

    - If you open the bleeder screw for only 1 full turn (360-degree turn) with engine still warm (do not remove it completely, only 1 full turn!), any trapped air will come out as a hiss (pretty much like a Cappuccino machine at Starbucks). When liquid comes out, close the bleeder screw.
    Look at the design of the bleed screw, it has a longitudinal slit running perpendicular to the threads. It is the slit that allows air to come out.
    For those worried about the screw coming out completely with 1 turn, no worry. I just checked with my own cars, it takes exactly five (5) full turns to completely remove the screw. So 1 full turn is all you need for air to escape.

    5. Lastly the complete overhaul written for 1998 528i is here if you need it. 1999-2003 is similar (check realoem.com for PNs and design):
    www.bimmerboard.com/forums/posts/199986

    6. Another tip: for 1-2 weeks after doing any cooling system work, carry some 50-50 coolant mix in the trunk and top it up as needed.
    In other words, keep a close eyes on the reservoir coolant level for 1-2 weeks. The E39 is notorious in terms of bleeding out air pocket.

    Good Luck and Have Fun!
    Last edited by cnn; 04-04-2010 at 12:09 PM.

  11. #11
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    In response to Cnn's post;

    In your number 2 section your flow path has an error. After leaving the lower radiator hose the coolant passes thought the thermostat and is pulled into the water pump and discharged under pressure out to the rest of the engine. when the thermostat is open, the flow of water from the cylinder head is restricted and is forced to flow into the upper radiator hose rather than being pulled into the water pump.


    How can air become trapped in the lower radiator hose? It is open through the hole shown in the video and in the images above, the air will purge through the hole as the coolant level rises in the radiator. Air cannot become trapped behind the thermostat unless the hole is plugged. Air on the inner side purges though the thermostat cover. for this car drilling a hole is of no benefit and does not aid the bleeding process. The actuation side of the thermostat is in the inlet to the water pump thus it is not possible for it to become airlocked as there would be no flow of coolant at all in the cooling system. The bleed hole is on the radiator side of the thermostat and allows any air trapped in the radiator hose to escape. Additionally the bypass from the block to the thermostat is connected to the upper radiator hose port, when the thermostat opens it also closes up the bypass from the block, forcing all flow to proceed into the upper radiator hose. if you view the front of the themostat cover you will see that the upper radiator hose port sits slightly higer than the top of the thermostat cover thus any air will be forced over into the upper radiator hose port and cannot become trapped in the thermostat cavity. This is immediatly visible if you view the installed image of the aluminum thermostat cover above.

    The image you provided is deceptive in understanding the flow of air based on the fact that it shows the engine in a vertical configurtation rather than in its installed inclined position which places the upper radiator hose port in the highest position in the block which allows any air to escape to the radiator.

    So far at least a half a dozen people have used this DIY instruction and have achieved a properly bled engine on the first time I would welcome you to provide links to people who have followed these instructions and failed to properly bleed the cooling system.

    Also it should be noted that this is BMWs procedure, Bentley has only replicated it, the procedure originated with BMW so I would like you to acknowledge that this is the case.
    Last edited by NNY528I; 04-04-2010 at 05:20 PM.
    >'97 528i, 200000 miles, Hella Xenons, 17" Stilauto wheels, Vogtland Drop Springs, Dynomax Race Muffler, Homelink, 540 brake upgrade, 15mm spacers >'65 & '74 MG Midgets BFC OT Lego Club #48 Manual conversion in process!!!



  12. #12
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    Re #2: When I wrote that coolant flow pattern, it is implicitly understood that once coolant enters the thermostat area, it is pumped by the WP. Maybe I did not make that clear but the above picture comes from BMW technical documents and it says it all. Just follow the Red (hot) and Blue (cool) arrows.
    It is essentially similar to any engine out there like Chevy, Ford, Mercedes etc. Nothing fancy: During "cold" phase, the coolant circulates only in the engine block. Once the tstat opens, the hot coolant is allowed to escape to the radiator.

    For those who wonder what is "air trapped behind thermostat", Google is your friend.
    The concept of "air trapped behind thermostat" is common knowledge for a long time, ever since the thermostat was invented by man.

    The following document is an excellent illustration of this concept. It usually happens when the thermostat is replaced (which is installed dry of course), then once the installation is complete, the coolant is filled, then air becomes trapped as shown below. Unless the thermostat has a mechanism for air to escape, air will be trapped. I believe Behr and Wahler design the tstat's "arrow area" with this purpose in mind. This is why they stamp the arrow on the thermostat.
    Personally, I think the arrow points to a "secret" area where Behr or Wahler creates a small air channel (very difficult to see with your eyes).

    On the other hand, as mentioned above, many thermostats come with hole already drilled from the factory. Just google "bmw wahler thermostat" and you see tons of these images.

    After work is performed on the cooling system (replacing tstat, WP, housing etc.):
    - If you who have no problem bleeding cooling system: great.
    - For those who have trouble bleeding cooling system (there are tons of these people on bimmerfest): be aware of the concept of "air trapped behind thermostat" and the possible remedies (drilling a hole in the tstat):

    http://www.tpub.com/content/aircondi...50-2540041.htm

    Figure: Air trapped in cooling system by thermostat being closed while system is filled:

    Last edited by cnn; 04-04-2010 at 07:35 PM.

  13. #13
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    The thermostat in the M52 type engines is not positioned like that, the thermostat is connected to the lower radiator hose, it is on the suction side of the water pump. When it is closed the opening into the engine block/head is open and the coolant circulates in from the block across the thermostat and into the intake of the water pump, there is no air on that side of the system which is different than the system you show above. The highest point in the system is the Upper radiator hose not the thermostat housing as shown in your photo. when the thermostat opens the opening to the block is closed and the opening to the lower radiator hose opens pulling coolant up from the bottom of the radiator across the thermostat and into the water pump.

    Air lock is a real problem, but it is not for this engine design with the thermostat located at the inlet to the water pump as BMW has located it, in order for the thermostat to become air locked the system must literally be dry from the water pump down.

    The arrow that you discuss is most likely a positioning tool to ensure that the thermostat is oriented correctly to the flow through the chamber, there is no air gap or space which you can check by shining a light around the sealing surface of the stat.

    The difference between what you posted above and the picture from the TIS is that the thermostat in a domestic type vehicle is located at the high point of the system, the flow through the block is pressurized as it enters the bypass around the thermostat, once the stat opens the feed through the radiator is a lower resistance path and the flow move though the radiator on the path of least resistance as it is pushed through by the water pump. In the BMW setup it is pulled through the radiator and the flow is actually switched from one side(the block)to the other(the radiator) by the action of the thermostat.
    >'97 528i, 200000 miles, Hella Xenons, 17" Stilauto wheels, Vogtland Drop Springs, Dynomax Race Muffler, Homelink, 540 brake upgrade, 15mm spacers >'65 & '74 MG Midgets BFC OT Lego Club #48 Manual conversion in process!!!



  14. #14
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    Great stuff... I recently had my Vanos rebuilt with the new O-rings and better tensioner etc. and experienced overheating after I got her back...I had done the coolant overhaul roughly 8 months prior and did the Hot bleed method without any issues...this time though, she would overheat at idle, not when moving though..I've bled it several times and I think I've finally got it...last two trips the needle has been a rock at dead center. I am tempted to go out and try this method right now though...

    One question, was the engine warm before you started ? or was it cold and you just crank the heat to max temp and low fan ?

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    Quote Originally Posted by CaptnGeetch View Post
    One question, was the engine warm before you started ? or was it cold and you just crank the heat to max temp and low fan ?
    Both bleed methods start with a cold engine.

  16. #16
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    Quote Originally Posted by jamesdc4 View Post
    Both bleed methods start with a cold engine.

    Thanx...figure that was the case so I just went out and did it..only difference I noticed...I have the stick in my tank..and with both bleeders the coolant level never got close to the top of the tank...but they both ran clean with no bubbles and the little overflow hole flowed steady too....ran it at idle for around 30 mins and the needle was stuck in the propper place...the temp did drop when I cranked the heat up for a bit...then leveled out.

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  17. #17
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    Cam and Jason,

    One thing we have never disussed (unless I missed a post) in our conversations about cooling system bleeding is the Bentley manual's warning (170-14) on not turning the ignition to the ON position for late model cars with a latent heat pump. Is it possible that some members who've had problems bleeding their cooling systems using the standard method might be owners with late model cars and the latent heat pump?
    ______________________
    Post mirrored as thread in E39 Main...
    ? to Cam and Jason on cooling system bleeding and latent heat pumps.
    Last edited by jamesdc4; 04-08-2010 at 07:30 PM.

  18. #18
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    Quote Originally Posted by jamesdc4 View Post
    Cam and Jason,

    One thing we have never disussed (unless I missed a post) in our conversations about cooling system bleeding is the Bentley manual's warning (170-14) on not turning the ignition to the ON position for late model cars with a latent heat pump. Is it possible that some members who've had problems bleeding their cooling systems using the standard method might be owners with late model cars and the latent heat pump?
    ______________________
    Post mirrored as thread in E39 Main...
    ? to Cam and Jason on cooling system bleeding and latent heat pumps.
    Well my first initial look at this question is that it may have something to do with the water valve in the latent heating system, in the older cars the heater core appears to be a side loop off the main loop, in the later cars, all flow from the expansion tank(where you add the coolant) seems to feed through the heater coor, it is also possible that the flow of the auxiliary coolant pump valve configuration actually reverses the flow through the engine/ heater core which would be counter productive to bleeding the system. I will look into this further as time permits to gain a better understanding of the flow pattern and the behavior of the water valve.

    As to your question I suspect it is possible, however I am inclined after observing 2 other people use this method to believe that it may be a question of not filling the tank properly rather than one of the flow. Both people I observed seemed surprised to have to fill the tank as high as they did during the bleeding, another seemed to feel this was a static procedure(IE fill once and all the air came out) after a little explaining I got them on the right track. This is part of why i wanted to prepare a video so people could actually see what they were supposed to do when they added coolant and what it would look like when the system was blead out which is a little difficult to explain in words but makes a ton of sense when you see it done.
    >'97 528i, 200000 miles, Hella Xenons, 17" Stilauto wheels, Vogtland Drop Springs, Dynomax Race Muffler, Homelink, 540 brake upgrade, 15mm spacers >'65 & '74 MG Midgets BFC OT Lego Club #48 Manual conversion in process!!!



  19. #19
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    Quote Originally Posted by jamesdc4 View Post
    Cam and Jason,

    One thing we have never discussed (unless I missed a post) in our conversations about cooling system bleeding is the Bentley manual's warning (170-14) on not turning the ignition to the ON position for late model cars with a latent heat pump. Is it possible that some members who've had problems bleeding their cooling systems using the standard method might be owners with late model cars and the latent heat pump?
    Dear James,

    Very interesting issue! I have the early 1998 528i model so no latent heat pump.

    For those who wonder what a latent heat pump is, it is small pump connected to #16 (the pump itself no number in this diagram):


    For model with latent pump, the following procedure is given to me by another person, so take it with a grain of salt.
    -----------
    "The procedure is same as above, but there are three additional requirements:
    1. After filling the expansion tank to the max. mark, the system must be pressurized to 1.5 bar using the type of cooling system pressure tester that fits onto the expansion tank neck.
    2. While the system is pressurized, remove the pollen filter and housing, open the bleed screw in the hose to the latent heat store. Once air bubbles cease to emerge from the bleed screw, tighten it securely.
    3. Now BMW test equipment must be connected to the diagnostic plug to activate the auxiliary water pump and latent heat store valve. After this re-open the bleed screw and went any air bubbles, disconnect BMW test equipment and relieve pressure in the system...."
    ----------

    Most of us don't have BMW test equipment, so the options are:
    1. Drive the car to dealer or suitably equipped specialist and let them do it with their BMW diagnostic equipment.
    But this is not cheap.

    2. In my case, I avoid the BMW dealer at all costs, and this is my suggestion for late model cars using "common sense" approach:
    - Follow Bentley instruction as above.
    - The key thing is to "fool" the HVAC system into the thinking that you activate the latent heat pump by:

    a. As above, run the engine until nice and warm. Stop engine, and pretend you go to a store shopping, so activate the "REST" button so the Aux Pump runs for a few minutes (maybe 3-4 min.).
    b. Theoretically any air trapped in the Aux Pump system is pumped into the main cooling system.
    c. Now run the engine again for about 3-4 min., but with HVAC set to Max Heat to open the Heater Valve.
    As the engine is still warm, the thermostat is still wide open, any air will be carried from the engine (or heater core) ---> coolant reservoir.
    This is because there is full flow of coolant (thermostat wide open).
    d. And Yes, if people do these steps with the front end raised, it will help bleed the air out.
    (Park the car on a sloped street is probably the easiest way).

    Repeat steps #a through d a few times, this should do it.

    Perhaps someone with a late model cars can try this trick and give us feedback!
    Last edited by cnn; 04-09-2010 at 09:20 AM.

  20. #20
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    Quote Originally Posted by cnn View Post
    Perhaps someone with a late model cars can try this trick and give us feedback!
    I'll do it and report back if and when I ever have a problem (knock on wood).

  21. #21
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    NNY528I : Very good DIY.

    Is there a other bleeding screw than the expansion tank with the m62 engine ?

  22. #22
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    I did some tensioner and pulleys last week, removed the fan/shroud and had to open the cooling system. Lost some coolant and decided to eff it, just flush and fill-in new stuff. I used the NNY528I method. I also broke a damned bleeder screw. Will buy some metallic ones from www.eactuning.com

    Thanks for this thread NNNNYYYY528.
    "I'd smash that (Jennifer Connelly) like a failed coup in sub-Saharan Africa."
    ~Macktheknife in my epic Jennifer Connelly OT Thread

  23. #23
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    Quote Originally Posted by Nic540 View Post
    NNY528I : Very good DIY.

    Is there a other bleeding screw than the expansion tank with the m62 engine ?
    no there is not another screw however the procedure is essentially identical without it, the M62 is actually a little easier to bleed due to the configuration of the heads and the upper radiator hose.
    >'97 528i, 200000 miles, Hella Xenons, 17" Stilauto wheels, Vogtland Drop Springs, Dynomax Race Muffler, Homelink, 540 brake upgrade, 15mm spacers >'65 & '74 MG Midgets BFC OT Lego Club #48 Manual conversion in process!!!



  24. #24
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    Nothing new, but the cooling system on the 6-cylinder engines has baffled me for a long time, why it is too difficult to bleed the air out etc.

    1. Take a minute to study the design of the E39 cooling system (see figure above for M54 engine).

    2. After some work in the cooling system is performed, re-filling the system is tricky because of the goofy design.

    I just took another detailed look at my car again and here is the trick.

    - Normally (if you haven't done any work on the cooling system at all) you want coolant at "KALT" level (or COLD level in the morning), but during re-filling, don't worry about it for now.

    - Look at the thermostat housing picture provided by NNY528i above (1st post), there is a small hole connecting the right and left sides of the thermostat housing. This hole allows air trapped in the lower radiator hose to travel through the hole to the driver's side to be bled out the bleeder screw. (See GREEN arrow).

    - If your car is on level ground, look carefully, you will see that the thermostat housing bleed screw (#1) is located at the same level as the reservoir neck and not at the "KALT" mark on the reservoir.

    - Once you understand the above design, re-filling is easy.

    a- Do it like NNY528i says. But I will add some tips...

    b- Be patient and be patient, the hole connecting the (R) and (L) sides the thermostat housing is very small, maybe 1/16" or something like it. So air bubbles move through it very slowly.

    c- Fill coolant up to the reservoir neck until it stops filling. Now some air is trapped in the lower radiator hose. Give it a good 5 minutes to settle there. Fill again until coolant fills to the reservoir neck, which is about 3 inches above "KALT" mark.

    In the mean time, listen to some music and drink some beer...

    d- Now open the thermostat housing 1 full turn (it takes 5 full turns to remove the bleed screw, so 1 full turn is all you need), air will come out slowly because the hole in the tstat housing is very small. When coolant comes out, close the bleed screw.

    e- Don't start the engine yet, repeat steps a through d a few times (another beer won't hurt...) until you are sure all air is bled out of the bleed screw.

    f- For the 1st fill, if coolant is at the reservoir neck, then it is OK, air trapped in the engine will be expelled out when you run the engine. It will eventually settle down to "KALT" level anyway. If you are worried, then use a turkey baster to remove a bit coolant so it sits just below the reservoir neck prior to running the engine.

    This should do it. Be patient and be patient when filling the cooling system!!!

    4. The above little trick will help get rid of air outside of the engine.
    Air Lock (air trapped inside the engine behind the thermostat) is another issue. Do a search.

    Last edited by cnn; 04-17-2010 at 08:52 AM.

  25. #25
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    Quote Originally Posted by cnn View Post
    Nothing new, but the cooling system on the 6-cylinder engines has baffled me for a long time, why it is too difficult to bleed the air out etc.

    I continue to be baffled by your insistence that it is difficult to bleed the cooling system on this car. I have produced a video showing how simple it is, i have provided simple step by step instructions and have numerous forum members who have used this procedure and have gotten a perfectly bled engine on the first try, including those who have had numerous issues that were solved once this procedure was followed.


    Quote Originally Posted by cnn View Post
    1. Take a minute to study the design of the E39 cooling system (see figure above for M54 engine).

    2. After some work in the cooling system is performed, re-filling the system is tricky because of the goofy design.

    I just took another detailed look at my car again and here is the trick.

    - Normally (if you haven't done any work on the cooling system at all) you want coolant at "KALT" level (or COLD level in the morning), but during re-filling, don't worry about it for now.
    It is not a goofy design, it is a relatively modern design that is in use on many modern vehicles.

    Quote Originally Posted by cnn View Post
    - Look at the thermostat housing picture provided by NNY528i above (1st post), there is a small hole connecting the right and left sides of the thermostat housing. This hole allows air trapped in the lower radiator hose to travel through the hole to the driver's side to be bled out the bleeder screw. (See GREEN arrow).
    So this you have finally understood, after having screamed to the heavens how stupid i was and how wrong i was to think this. this hole prevents any pocket of air in the lower radiator hose. The flow of air is very quick and there is really no delay in the air working its way through the system.

    Quote Originally Posted by cnn View Post
    - If your car is on level ground, look carefully, you will see that the thermostat housing bleed screw (#1) is located at the same level as the reservoir neck and not at the "KALT" mark on the reservoir.

    - Once you understand the above design, re-filling is easy.
    This in not correct, they are not at the same level, however the thermostat cover bleed screw is really redundant in the design as all air in the system will end up in the top of the radiator(there is a small pocket in the middle of the thermostat cover but it is very small) where it can be bled using the bleeder on the expansion tank as is done on the V8s.

    The level of the cold mark and the position of the bleeder screws have no relation to one another. the cold mark is the level that allows the coolant to expand while still leaving a sufficient air cushion to allow the system to maintain a steady pressure without coolant loss, it is based solely on this. the bleeder screws serve only to evacuate air from the system and are positioned at the highest points in the system to allow air to escape.

    Quote Originally Posted by cnn View Post
    a- Do it like NNY528i says. But I will add some tips...

    b- Be patient and be patient, the hole connecting the (R) and (L) sides the thermostat housing is very small, maybe 1/16" or something like it. So air bubbles move through it very slowly.
    Actually air moves through the hole quite quickly, coolant far less so which is why the system does not short circuit. The bleeding seen in the video which is real time resulted in a car that maintained a level after bleeding of about 2 inches above the cold level in the expansion tank, there was no air left in the system when done, and no extra time was required to achieve this but that which is shown on the video. When the video ended, we went for a drive.

    Quote Originally Posted by cnn View Post
    c- Fill coolant up to the reservoir neck until it stops filling. Now some air is trapped in the lower radiator hose. Give it a good 5 minutes to settle there. Fill again until coolant fills to the reservoir neck, which is about 3 inches above "KALT" mark.

    In the mean time, listen to some music and drink some beer...

    There is no air trapped in there and it does not take an excess time for the air to come out, it is coming out as the level of the coolant in the radiator rises, almost as fast as the coolant reaches the radiator, level at the lower bleeder was achieved within a couple of minutes while filling as can be seen in the video.

    Quote Originally Posted by cnn View Post
    d- Now open the thermostat housing 1 full turn (it takes 5 full turns to remove the bleed screw, so 1 full turn is all you need), air will come out slowly because the hole in the tstat housing is very small. When coolant comes out, close the bleed screw.
    I specifically excluded this approach to using the bleeders as it is difficult to see when the air is bubbling out and it increases the potential to damage the bleeder screw threads. It is FAR simpler and FAR easier to see when bleeding is finished if the screws are removed completely at the start of procedure and installed only when air free coolant flows from the opening. once this occurs there is no need to reopen the bleeder screws. This is clearly shown in the video and it works great every time. no need for repeats or additional cycles as you indicate below, which is all unneccessary if the procedure is followed as described and as shown in the video, this just complicates a simple procedure.

    Quote Originally Posted by cnn View Post
    e- Don't start the engine yet, repeat steps a through d a few times (another beer won't hurt...) until you are sure all air is bled out of the bleed screw.

    f- For the 1st fill, if coolant is at the reservoir neck, then it is OK, air trapped in the engine will be expelled out when you run the engine. It will eventually settle down to "KALT" level anyway. If you are worried, then use a turkey baster to remove a bit coolant so it sits just below the reservoir neck prior to running the engine.

    This should do it. Be patient and be patient when filling the cooling system!!!

    4. The above little trick will help get rid of air outside of the engine.
    Air Lock (air trapped inside the engine behind the thermostat) is another issue. Do a search.



    You still are not understanding the design of this cooling system. The thermostat is positioned on the suction side of the water pump, which means that it is NOT POSSIBLE for it to become air locked. It simply cannot occur, any air in the system flows to the high point which is not the thermostat cavity but rather is the upper radiator hose and ultimately the top of the radiator. There is a passage that connects the upper radiator hose and the back(engine block) side of the thermostat chamber(which is also the inlet to the pump. when the thermostat opens, its closes of the back of the thermostat chamber while opening the lower radiator hose. The flow from the engine is drawn out to the radiator through the aforementioned passage and up through the upper radiator hose. There is no air lock, there is no where for the air to be trapped as the high point of the block is the upper radiator hose port. This passage is shown in the diagram you posted of the cooling system. It is the orange arrow shown leaving the cylinder head and branching in 3 directions, 1) to the inlet of the pump(the thermostat chamber), 2) the upper radiator hose and 3) to the heater core(it is pulled in via the coolant auxilliary pump, early cars may be different)

    The procedure I provided works perfectly, it has been validated by numerous people with no issues that I am aware of and has worked every time, whether by skilled mechanics or by neophytes it has worked for all just as it is written.
    >'97 528i, 200000 miles, Hella Xenons, 17" Stilauto wheels, Vogtland Drop Springs, Dynomax Race Muffler, Homelink, 540 brake upgrade, 15mm spacers >'65 & '74 MG Midgets BFC OT Lego Club #48 Manual conversion in process!!!



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