overheating

[Group A]

i have a 86 325 and it overheats after about 10 minutes of driving (temp needle between red and 3/4). when idling the temp will sit right behind the 3/4 and when driven it will rise. i put in a new t-stat thinking that was the problem, but i guess not. my next guess is the waterpump, any ideas guys? and how hard is it to put in a waterpump, will i have to take out the radiator?

[lordofthewaters]

My jeep (that I no longer have) did this, and it turned out to be the cat. It'd idle fine with no apparent problems. But when you tried to drive it would lose power and overheat. Turns out the cat had broken up and the exhaust pressure was pushing the fragment and closing off the outlet...........

[Group A]

why hasnt anyone else replied?!!??!!??!!??!!

[Adrian_Visser]

before you go and spend money on a water pump think about your cooling fan. its the clutch type is it not? the clutch in it is probaly worn out get a new one. to check this warm up your engine and while stopped and idling listen for the fan. if you dont hear much noise from the fan when your engine is on the hot side then its probaly the fan.

[King Luis]

fan clutch, coolant and make sure your rad is in good condition.
check the simple things before wasting money on a water pump that might not need replacing.

[n3nyongmini]

um yeah

King Luis right.

doesn't sound like a water pump to me.

:t-stat check
:fan clutch
:radiator
:maybe cat.

good way to narrow down to fan clutch and/or radiator - turn your A/C on. It'll run your condensor fan which will move additional air across the radiator...
If it helps alot, it's prolly the clutch, if it doesn't, look at radiator flow/blockage (flush it).

Then:

Another narrow down: warm it up idling to operating temp w/o pressure cap. Put cap on, keep idling, blip throttle a few times, rev a bit (3k or so enough). Watch temp - slowly take off cap. If you got alot more temp or pressure while cap on - think head gasket or similar.

With bad fan clutch I would suspect temp to go down with driving (more air), but you say it goes up. I suspect radiator or gasket.

HTH - GL

[RobertK]

I would be cautious running the car for too long once it passes the 3/4 mark on the temp guage. You run the chance of warping the head, cracking it, or blowing the head gasket.

[87-325ic]

dont run far past the 3/4 mark. just dont.

IF ITS THE FAN CLUTCH..
then at driving speeds you should cool off (since air passes through the radiator then, with bad fan, it doesnt at idle)
i dont think its your clutch for the Most part.

Maybe radiator, Could be blocked, check and if not.. look to the water pump.

more friction= higher heat while you are driving, thats where this problem comes from..

you say you just replaced your t-stat? def look to blocked Rad.. and then water pump.. also, dont forget a good flushing might help too..

and about the cat.. possibly?

[rob_e30]

Here is a simple check for radiator flow... check the top hose while the car is hot. If the top hose is cool then no coolant flow through the radiator (bad pump or t-stat). Do you get hot air from the heater? That's also a check for coolant flow/bad water pump. Is it cool when driving but temp creeps up when stopped? If so then it's the fan clutch. Are you loosing coolant? If so then get prepared for a head gasket.

[Group A]

the t-stat is not the problem. like i said i replaced it. the fan is working ( i think) i can see it spinning. and even if it was only the fan thats the problem, that doesnt explain temp rising while driving at speed.

the hose thats connected to the t-stat housing does not get hot, even after the temp rises pass 1/2 way.

it COUOLD be the cat, because the exhaust does rattle a bit, like theres loose chunks in it. is there a easy way to check if its the cat?

and whats the proper way to drain and flush the E30? im a n00b with BMWs, im more of a honda/japanese import guy.

[lordofthewaters]

As far as checking the cat goes, the only way I know to test it for sure is to pull it, and see. If your emissions rules for your 86 will allow it, I'd suggest hollowing out your cat anyway.........

[rob_e30]

A plugged cat would cause the engine to generate too much heat, more than the cooling system can keep up with (similar to a blown head gasket). You said the top hose does not get hot, this indicates that coolant is not circulating. What happens with the in car heater? If no heat in the car that is another indication of poor circulation. I think you have a circulation problem. You might also have air trapped in the system. How is your coolant level and have you bled the system? With the t-stat open the top hose should be something close to 180' (or better if it's running hot).

[King Luis]

A plugged cat would cause the engine to generate too much heat, more than the cooling system can keep up with (similar to a blown head gasket). You said the top hose does not get hot, this indicates that coolant is not circulating. What happens with the in car heater? If no heat in the car that is another indication of poor circulation. I think you have a circulation problem. You might also have air trapped in the system. How is your coolant level and have you bled the system? With the t-stat open the top hose should be something close to 180' (or better if it's running hot).

if it is the cat check how much air is coming out of the exhaust....see if when you rev it, if its less then it should be...that should be a very simple diagnose of it.

[Group A]

the exhuast gas a good amount of airflow, it seems normal to me. but there is ALWAYS hot air coming out of the vent, even at full cold. i bled the system, but not sure if i did it correctly. i ran it with the resovoir cap off and open the bleed screw on the t-stat housing til a smooth stream of coolant flowed out, is that correct?