Bleeding Question, How to make sure there is on more air left in the system?

[Akhil]

Hi Guys.

I am back. At last I replaced thermostat and water pump, fix thermostat housing leak and refilled the system. Thanks to all of you guys who help me do diagnose the problem and guided me to right direction in my previous post "Italian tune-up caused over heating".

I drove few miles after this and temp stayed on half (12:00 O'clock position), which I think is suppose to be.

My question is I did the bleeding, but not sure I got ride of all air or not. Is there any way to make sure there in no air in the system? If air is left in the system, what are the symptoms of that?

My another question is, after I drove 6-7 miles and let the car rest for few min and when I came back and turn the ignition ON (did not start yet), then I saw the temp was about little less than 3/4 on gauge. But as I started my car, within few seconds temp came back on half. I could not understand it, how come coolant getting hotter when engine is of and came back to normal when I start the engine. Another thing I observed is, after driving when coolant got hot (normal operating temp) but expansion tank level was still the same as it was on cold.

Can you guys get any clue from these weird symptoms? I would appreciate any help or comment.

Thanks a lot.

Best Regards,
Akhil

[uscharalph]

Hi Guys.

I am back. At last I replaced thermostat and water pump, fix thermostat housing leak and refilled the system. Thanks to all of you guys who help me do diagnose the problem and guided me to right direction in my previous post "Italian tune-up caused over heating".

I drove few miles after this and temp stayed on half (12:00 O'clock position), which I think is suppose to be.

My question is I did the bleeding, but not sure I got ride of all air or not. Is there any way to make sure there in no air in the system? If air is left in the system, what are the symptoms of that?

My another question is, after I drove 6-7 miles and let the car rest for few min and when I came back and turn the ignition ON (did not start yet), then I saw the temp was about little less than 3/4 on gauge. But as I started my car, within few seconds temp came back on half. I could not understand it, how come coolant getting hotter when engine is of and came back to normal when I start the engine. Another thing I observed is, after driving when coolant got hot (normal operating temp) but expansion tank level was still the same as it was on cold.

Can you guys get any clue from these weird symptoms? I would appreciate any help or comment.

Thanks a lot.

Best Regards,
Akhil
The coolant can continue to get hotter when you turn off the engine as it is no longer circulating and you have no air coming thru to cool it, but 3/4 seems to be a little extreme. It's hard to say, but it probably still needs bleeding. Also, did you replace the radiator cap? Those thing only have a limited amount of overheating in them.

[mbogosia]

I kinda had the same question. I replaced my expansion tank o rings today and had to drain and refill the system. I bled it about 4 times and it has been fine. Do I just watch it and if it acts up(overheats) bleed it again, or should I bleed it several times over the next couple of days?

[Akhil]

No. I did not replace the radiator cap. It seems file to me. Is it one of the truble point too? Why not the coolant level in expansion tank going up after heating? It use to go up after heating before I had water pump broke and I had to refill the system.

[Dan in NZ]

Check the www.bmwe34.net site, it has a page on the "heat soak" thing. Don't worry, it's normal for the coolant to heat up a little after it's been parked for a short time, just the residual heat from the engine...

[Akhil]

Thanks a lot guys for all you reply and help.

But still have one question. Why isn't my coolant level rising in exp. tank after being driven to bring normal operating temp. range? Any Clue?

Regards,
Akhil