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Discussion Starter #1
Short version: I think there is air in the AT cooler portion of the cooling system.

Any ideas?

Longer version:
My 325I developed a slow coolant leak from the water pump at 110K. I bought and installed a kit with a water pump, radiator, hoses, thermostat and housing, expansion tank, and fluid. Two weeks later it was leaking somewhere under the expansion tank. Grrrrr! I ended up replacing the mounting plate(17111436251), AT tstat( 17111437362 ), and expansion tank (OEM this time). No leaks again for a week with daily driving. Then it started leaking AGAIN! This time it was from the return hose(11531436410) which I replaced and it still leaked. So finally last week I replaced the coolant connection fitting(17111707817) which seems to have stopped the leak but now I can't get the system bled correctly. I used the procedure in the Bentley manual, climate control on full hot, fan on low, open bleeder and add fluid to the expansion tank. The car was parked on a slight incline with the front higher than the back. I can't get all the fluid back in the system that I drained out the last time. The car runs fine, heater and AC work, temp gauge is straight up, but there must be air in the system somewhere. The expansion tank was a real bitch to get seated correctly. I am thinking there is air in the AT cooler portion of the system.

Any ideas?

http://www.realoem.com/bmw/enUS/showparts?id=ET37-USA-03-2002-E46-BMW-325i&diagId=17_0215

http://www.realoem.com/bmw/enUS/showparts?id=ET37-USA-03-2002-E46-BMW-325i&diagId=17_0141
 

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I actually have always had better luck bleeding the cooling system with the front end elevated. I once fought with it for over an hour on level ground until I drove the front up on ramps. It very quickly burped out the rest of the air. Now that's how I always do it and bleeding is fast and painless.
 

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I actually have always had better luck bleeding the cooling system with the front end elevated. I once fought with it for over an hour on level ground until I drove the front up on ramps. It very quickly burped out the rest of the air. Now that's how I always do it and bleeding is fast and painless.
+1. I did mine with the front up on jackstands. Bleeding was no issue.
 

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Discussion Starter #5
Thanks for the replies Guys!

Elevated front always worked well for me in the past. It worked 4 times recently just not this last time. Maybe I over filled and or filled to quickly. Anyway that could be a problem? I would really like to get this coolant system sorted out and be done with it!
 

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I once used an e39 TSB from BMW which gave instructions to rev a stone cold engine to 3-4K RPM 3-4 times without exceeding 30 seconds of run time with the expansion tank cap loose to vent any air bubbles that may be in the system. I had trouble with bleeding my car but after following the TSB the fluid level in the cooling system is stable.
 

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Discussion Starter #7
Thanks Synrgy, I will have to wait till tomorrow for a stone cold engine to give this a try.
 

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Discussion Starter #8
Well, revving the engine with the expansion tank cap loose did not help burb the system. Actually I took the cap off, and it sprayed coolant all over the engine. I won't do that again! DUH! So I guess I'm going to drain the system, and take the expansion tank off again and try putting it all back together.

Any trick to getting the expansion tank seated easily\properly?
 

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Well, revving the engine with the expansion tank cap loose did not help burb the system. Actually I took the cap off, and it sprayed coolant all over the engine. I won't do that again! DUH! So I guess I'm going to drain the system, and take the expansion tank off again and try putting it all back together.

Any trick to getting the expansion tank seated easily\properly?
Sorry man, but yeah you're not supposed to take the cap completely off or else coolant sprays out, should have warned you. Not sure what else you can do to burp the system, again this was from a BMW technical article if you have problems purging air from the system. Good luck!
 
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