Cooling system problems

[Big Red M3]

I recently bought a 1995 BMW M3 froim my father in law. When I got it home the car started overheating. Ichecked the BBS and saw the problems with the stock water pump, so I replaced the water pump, hoses, thermostat, fan clutch, etc. When I pulled the water pump out of the engine, it was demolished. It had completely torn apart. I got most of the pieces out, that I could find and spoke with a mechanic relative of mine. He said any small pieces which remain in the engine should not cause a problem, since the water flows throught the engine at a relatively slow rate. I did flush the engine and radiator but not many pieces came out. I put the car together, with a water pump provided by Pelican Parts. Now the car heats up faster that it used to (I got the thermostat from Pelican parts as well) I don't know the temp of the thermostat.

After driving a while and turing the car off, I get a "Check Engine Coolant" message on the in car computer. The car never over heats and runs well. My question is what is going on? I check the coolant level and it is at the mark. Does anyone have any suggestions? I'm at a loss. Do you think the pieces of the water pump which may still be in the engine are causing this?

PLEASE HELP, I don't want to screw up my engine.

[Jared at Pelican Parts]

I'd do a compression check on the motor to see if it blew the head gasket when the car overheated.

[Jeron]

I get the same message and I'm almost positive it is merely the coolant level sensor. I plan to replace it when I do my next coolant change.

If you are not having any other problems and your coolant is topped up then it's just your level sensor.

The coolant temp should rise quickly in the summer but I'm not sure what you are comparing it to. If you mean faster than when the pump was not functioning then I wouldn't worry about it.

Are both of your fans working?

[Jared at Pelican Parts]

I'll also ask if you bled the system completely of air.

[jamin325i]

i overheated once with a failed oem waterpump.
i also replaced my failed thermostat. now, my gauge goes to midrange within 5 minutes consistantly.
on other occasions my coolant message-on obc- alerted me to a low coolant level when the level was o.k. i fixed it by changing out the coolant level sensor in the overflow tank.
it doesnt appear you have any other problems if there are no other symptoms, like drivability, white smoke, loss of coolant, water foam at oil system outlets, etc...

[Jared at Pelican Parts]

I'd still do the compression check though just to be sure. I overheated and blew my head gasket, and had none of the obvious signs of a head gasket blow..

[Big Red M3]

Thanks guys, I'll do the compresion check, but I have not had any trouble with the engine running at all, No leaks, no smoke nothing. I was leaning toward a sensor, but didn't know. I did bleed the coolant, which took forever I might add. I appreciate the help! I'm glad to know the temp going up (to normal) fast is not unusual.

[Jeron]

Just an FYI. The coolant gauge on the 97+ E36 has an almost 50 degree range which is TDC. Meaning from about 176-220 degrees the gauge will read 12 o'clock but once it move toward hot there are only about 11 degrees before red. I can't remember when they went to the idiot gauge but it may be on all E36.

My point is that although it appears that the car heats quickly to normal operating temperature and stays there, the truth is that it heats quickly to 176 then continues to move toward its normal operation temperature. And although the gauge stays steady at TDC there are actually temperature fluctuations that the gauge will not reveal.

You can get the true "raw" temp on the OBD-II cars using a test mode on the instrument cluster but I don't know if it is possible on the OBD-I 1995 M3.

[stupenal]

Originally posted by Jared at Pelican Parts
I'll also ask if you bled the system completely of air.

Thats a very very good point. If the system is not completely bled of air, the thermostat doesn't have enough coolant to open. When I was getting all my cooling system changed, my mechanic was extremely puzzled to see that the car was heating up yet no coolant was flowing into the engine. I kept wanting to scream at him - PUT IN MORE COOLANT! But I kept my cool and he figured it outr after 3 minutes. Also - you probably already know this - but its always good to point out: BE VERY CAREFUl with the bleed valve screw! its VERY VERY easy to overtighten and break as it is plastic!

[Big Red M3]

Thanks alot guys, I new I would get some good answers if I posted on this site. It's cool to be in a "fraternity" of people as interested in these cars as I am.