*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.
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