6 Cylinder Coolant Bleed Troubleshooting

[aadznt]

Hello all,

I'm doing a coolant bleed/top up after replacing my alternator and oil filter housing gasket and I can't seem to figure out what I'm doing. I've read that to properly do this, you open both thermostat and expansion tank bleeders, run the heater on max temperature with low fan speed, then wait to see bubble-free flow from the thermostat and then expansion tank bleeder (all the while adding coolant).

My confusion relates to the expansion tank float, which in theory should be level with the brim of the expansion tank cap, though the float goes up and down depending on whether the bleeders are open and whether the heater is running. Images and videos linked to show what I mean. I'm also unsure what to do, as I have intermittent flow from the thermostat bleeder, which is relatively bubble-free (see video).

Video of bleeders with heater running.
(https://sendvid.com/wedrzvk3)
Images of float with bleeders open/closed etc.
(https://imgbox.com/g/mb5N4xXfi3)
I have the following questions:



When using the float to gauge fill level, should the bleeders be open or closed? And should the heater be running?
Does my coolant seem high or low based on the images/video?
Based on the media, should I:


a) Continue to let the heater run while topping up coolant and hope that the flow from thermostat bleeder becomes steady?
b) Let the heater run while NOT topping up coolant and let any potential excess fluid drain out that way?
c) Something else?


Thanks in advance for your help! I appreciate it.

[jicaino]

This is how I do it, I have been doing it for all my e39ing life and on all cars, all engines.
I jack up the nose, or I drive up a ramp or an incline where the front axle is at least 4" higher. I crack open the expansion tank bleeder screw (don't remove it jus crack it open) and pour 65% of the nominal or estimated coolant thru the top hose (the hot side of the radiator, I remove the hose rad side and pour thru that hose). After I hear gurgling near the hose nipple inside the radiator, I set the heater on max temp min airflow, close the rad hose and continue pouring thru the expansion tank. I massage the top hose to drive out air bubbles, and in the 6 cyl I blow thru the expansion tank opening. Then with no expansion tank cap and the bleeder cracked open, I start the car and give it 4/5 runs up to 3000 rpm. Leave it on, go check until the bleeder screw pours out a steady stream of coolant, close it, and keep on letting it idle until the top hose is hot (sign of the thermostat having opened) and starting to flow into the expansion tank via the equalization hose (the skinny hose under the shroud, connecting the radiator with the expansion tank).
At that point I add coolant up to the neck of the expansion tank and cap it. Then I recheck level the next day when dead cold. Usually that ends up right on the money or you may have to add a cup or two of coolant.

[TiesTorN]

you don't need to struggle for hours for just some small bubbles in there. after filling most of it, just daily drive your car (with eyeballing temp gauge and using heater occasionally), park it, check the fluid level next morning when it's dead cold, top it up. rinse and repeat for a few days. when you don't need to top up anymore bleeding is complete. that's what I always do.

[jicaino]

you don't need to struggle for hours for just some small bubbles in there. after filling most of it, just daily drive your car (with eyeballing temp gauge and using heater occasionally), park it, check the fluid level next morning when it's dead cold, top it up. rinse and repeat for a few days. when you don't need to top up anymore bleeding is complete. that's what I always do.

The 540i is the easy one re. Cooling system.

[effduration]

jicaino's method should work.

Whatever you do, learn to unlock the cluster menu and set it to test#7 while driving for the next few days and watch it like a hawk. Temps should not go above 100c for long on an I6 and if they reach 105c you have a problem for sure. The coolant temp gauge is nearly useless.

[Jason5driver]

This is a great thread , specifically for flushing …
Post #6 …
https://www.bimmerforums.com/forum/showthread.php?1150494-THERMOSTAT-Head-Corrosion&p=30920715#post30920715

[aadznt]

Thanks all, took it on a 170 mile intercity trip and all was well with the coolant temps

[jicaino]

great! congrats.