M62B35 - Bleeding cooling system question

[mcx]

Hello guys,

So after I have changed the radiator and the hoses, and the clamps. I filled up the cooling system, I believe I will still need to change the valley pan sealings. But that comes right after I will do big maintenace and change the sealings on my valve covers, spark plugs, engine mounts, and intake sealings. Well, let's not get off-topic here.

When it comes to bleeding the V8 system, I have stumbled upon different guides even in E39 V8 service manual. (the one with 1500 pages). That I should put my car in incline, set key into the position 2 and set heater to 32 celsius degrees and slowly add coolant to expansion tank, whils having the bleeding screw unscrewed and wait until it will spill coolant.

Nice theory but, the water level in expansion tank has lower water level than the top of the bleeding screw, and for the love of god I cannot figure out how it is possible if I fill something essential from the bottom, how it can come out of the top ?

Only way that I could think of is to let the engine cool down over night, and then slowly add coolant whilst engine was running with the heater set to 32 degrees and fill it up as the engine sucks in water from expansion tank.

Can someone elaborate how these guides are meant to be understood for someone like me with not that much experience in this area. I have troubles understanding how does it work in E39 V8 cooling system (For Example. I have Nissan Patrol, and you have 2 expansion tanks there, 1 which you full all the way to the top. and the excess will overflow to the other tank, and you keep filling that 1st tank up whils the engine is running and bubbles goes to the excess tank. That I understand because it is the highest point in cooling system).

Thank you for your informations, I have been scratching my head over this one for a quite a long time.

(Also my TEMP gauge is going from 0celsios to 100 celsius and when I pulled out the On-board diag menu 7, KTMP is just jumping from like 20-30 celsius to 90 celsius and it keeps doing that randomly).

Thank you again for any help and clarification. :)).

Happy new year everyone o/

[scubajim20]

The expansion tank will appear empty when the system is bled correctly. The tip of the red wand should just appear at the neck of the tank. I did a search in this forum and watched the youtube video. I just did mine a few weeks ago and it went smoothly. If you have a quick jump in temperature I think you are still dealing with air in the system.

[Jaaap]

^^ What scubajim said.
Also, you are overthinking this.
Put car on incline (or jack the nose up a bit), run engine, add water to exp. tank for a while.
Rev it to 2.5/3k for a couple of seconds to get the bubbles out.
DONE.

[BimmrMeUpSnotty]

Really, the V8 does not need to be raised in the front. It should be done on the i6’s, but the V8 is very easy to bleed without raising the front end. So, bleed that sucker and be done. If you have the red floater stick sticking up above the port of the expansion tank, you overfilled it. The top of the stick should be in line with the threads for the cap. I actually keep it lower, it is an expansion bottle.

[CSMBlack-540i]

Nice theory but, the water level in expansion tank has lower water level than the top of the bleeding screw, and for the love of god I cannot figure out how it is possible if I fill something essential from the bottom, how it can come out of the top ?

Only way that I could think of is to let the engine cool down over night, and then slowly add coolant whilst engine was running with the heater set to 32 degrees and fill it up as the engine sucks in water from expansion tank.

Can someone elaborate how these guides are meant to be understood for someone like me with not that much experience in this area. I have troubles understanding how does it work in E39 V8 cooling system (For Example. I have Nissan Patrol, and you have 2 expansion tanks there, 1 which you full all the way to the top. and the excess will overflow to the other tank, and you keep filling that 1st tank up whils the engine is running and bubbles goes to the excess tank. That I understand because it is the highest point in cooling system).

Thank you for your informations, I have been scratching my head over this one for a quite a long time.

(Also my TEMP gauge is going from 0celsios to 100 celsius and when I pulled out the On-board diag menu 7, KTMP is just jumping from like 20-30 celsius to 90 celsius and it keeps doing that randomly).

Thank you again for any help and clarification. :)).



If I'm reading your theory correctly, you understand the theory as it applies to the Nissan but not understanding how it applies to the V8.

It is essentially the same. In basic physics, air is lighter than liquid and rises to the highest point when possible. By elevating the front of the car, you are helping the air to circulate to the top when combined with the suggestion that the engine is turned on with heater on full.

While it is not necessary to turn on the engine, turn on the heater to max or elevate the front, these are all just methods in combination that help to move that air quicker thru the system and to the bleeder screw.

The fact your temp gauge is jumping around 90 celsius indicates there is still more air trapped in the system. Once it is properly bled, the temperature should stabilize.

What you may not realize is the the bleeder screw is also fed air from the top of the radiator since there is a hose that runs along the top of the radiator to the driver's side nipple and air gets trapped in the top of the radiator too. So alot of that trapped air is moved along the hose to the bleeder screw when pressure builds as the engine warms. At least it does on the 4.4 V8, not sure of the 3.5 V8 you have is the same setup though.

It may also be helpful to look at a diagram of the coolant flow on the V8, when you pour coolant into the expansion tank, it gets sucked into the bottom of the water pump, flows thru the engine then to the radiator. It doesn't directly flow to the bleeder screw until it passes through the system.

There was a thread here about the I6 M52, M54 too and the theory is the same. It all comes down to coolant flow.

https://www.bimmerfest.com/forums/showthread.php?t=449008

[mcx]

If I'm reading your theory correctly, you understand the theory as it applies to the Nissan but not understanding how it applies to the V8.

It is essentially the same. In basic physics, air is lighter than liquid and rises to the highest point when possible. By elevating the front of the car, you are helping the air to circulate to the top when combined with the suggestion that the engine is turned on with heater on full.

While it is not necessary to turn on the engine, turn on the heater to max or elevate the front, these are all just methods in combination that help to move that air quicker thru the system and to the bleeder screw.

The fact your temp gauge is jumping around 90 celsius indicates there is still more air trapped in the system. Once it is properly bled, the temperature should stabilize.

What you may not realize is the the bleeder screw is also fed air from the top of the radiator since there is a hose that runs along the top of the radiator to the driver's side nipple and air gets trapped in the top of the radiator too. So alot of that trapped air is moved along the hose to the bleeder screw when pressure builds as the engine warms. At least it does on the 4.4 V8, not sure of the 3.5 V8 you have is the same setup though.

It may also be helpful to look at a diagram of the coolant flow on the V8, when you pour coolant into the expansion tank, it gets sucked into the bottom of the water pump, flows thru the engine then to the radiator. It doesn't directly flow to the bleeder screw until it passes through the system.

There was a thread here about the I6 M52, M54 too and the theory is the same. It all comes down to coolant flow.

https://www.bimmerfest.com/forums/showthread.php?t=449008

Thanks for the information. Yes I understood it as a Expansion tank should be the highest point, therefore no need to put it against the hill. to make voodoo magic near the cooling system or praise the Slavic gods whilst butchering a lamb as a part of a bleeding procedure.

But from what the informations I have gathered I have no options left.

And yes you are right I have the air trapped in the hose you describe right side if you are standing in front of the car. I keep squeezing it and I can hear the bubbles there, but it seems that I will have to repeat the bleeding process several times, I still have a leak somewhere, and I belive it is along the valley pan. Because I can smell burning coolant whenever I drive somewhere and get out of the car. Since I am not able to find a leak underneath the car, and I am in active denial that it might be the head gaskets (no white smoke that burns in your nose after the start and othe symptoms of head gasket I have not noticed with my BM).

[jicaino]

I pour 10 liters, then start the engine with the bleeder screw off and cap off (IKHA at top temp lowest fan setting) as it warms up I keep adding, when bubbles stop from the bleeding port I close it, when the water is hot and the thermostat starts to open I add the last bit, stop the engine, add until the wand is about 2" above the neck and close it. Remove the bleeder for the last burp and it's done. I check after dead cold temp (12+ hours of sitting oevrnight) Usually it's right on, sometimes you need to add a cup of two.

[CPHES]

Keep it a bit under filled - counterintuitive, but coolant expands, as it gets hotter. The red stick should be visible, but below the lower edge of the threads

[BimmrMeUpSnotty]

Yep, if the stick is sticking out, it's overfilled.

[jicaino]

Yep, if the stick is sticking out, it's overfilled.

when cold, right? When hot, that stick it's always like in our 20's :rofl

[BimmrMeUpSnotty]

52 years old, still keeping it up, no blue pill, life is good!

[jicaino]

52 years old, still keeping it up, no blue pill, life is good!

47 here. Same as you, no blue pill and life's peaches. But don't tell me it's like when we were in our 20's. I still remember how my 540i rode when it was below 70k miles :rofl

[TheTailor]

I wonder if your aux water pump is working, you getting super hot air from your heater when the temp is up?

Sent from my SM-G950U using Tapatalk

[theWalkinator]

Just a tip to speed up bleeding process, raise the front end, remove upper radiator hose at radiator, pour coolant from upper radiator hose, connect upper radiator hose back to radiator, do the rest of filling and bleeding at expansion tank, set heat at highest and fan at lowest, fire it up, let it idle for while, keep filling coolant at expansion tank, squeeze upper radiator hose to help coolant flow, when car is warm up, keep engine running at 2500rpm for 30 seconds or so, do this few times then re-check coolant level, close expansion tank cap, loosen bleeding screw to let air out, squeeze upper radiator hose few times again, tighten bleeding screw when only coolant come out bleeding screw, you should be good. Let the car cool down and re-check coolant level, you may need to add little coolant if needed.