plumbum

I have been reading a lot and not sure if my issue is the same as some others except with different symptoms.

First off the car is a 1989 944S2
I noticed a small drop of coolant under the area of the oil cooler on the right side of the block..I cleaned the area and ran the car, no more leaks however when I had the car running for 20+min at idle I noticed the car was starting to overheat and the gauge was just above the upper limit (not in the red). I raised the RPM and the level went down but would clime if left to idle.

I noted that heat in the car goes from hot to cold..as if there is air in the system. The coolant reservoir is always cold.

The system has not been opened and there are no leaks.

There was pressure in the expansion tank and after slowly releasing the cap and letting the car cool for 30min I removed the cap and started the car. There was air coming into the expansion tank which then stopped and things seemed normal however it did start to get hot again which dropped to normal or even low on the gauge when I raised the idle to 2k.

The issue is acting like there is air in the system-could someone point me to the proper bleed procedure (there are lots of posts about different ways to do it) I am hoping that is my only issue but fearing the worse, a head gasket or head. Is there anything else I could check? The level seems over filled from the PO however I drove it like that for a few months last summer and there were no issues.

I have only had the car out once this year and it did not overheat while driving.

Thanks in advance

konakat

This sounds like just air in the system. Jack up the front end and turn the heater to full hot. Open the bleed valve then apply pressure to the coolant tank. Add more coolant to the tank if necessary and keep applying pressure until you start getting coolant flowing out the bleed valve. Close the valve, top off the coolant, and you're good to go.

plumbum

I like what your saying! Will try that tomorrow morning and report back! My only concen is how it got in there in the first place

konakat

Ah, yes. That is the rub.

flash75

Are your cooling fans on when the gauge is near the red zone? They should be on if the engine is hot. Is the upper radiator hose and the top of the radiator hot? With a normal system those areas should be hot when the gauge shows normal or above.

You don't know the system is right unless the fans are working correctly.

Clifton

konakat

The fact that the heat stops working periodically means that he has air in the heater core. There may be other issues, but bleeding should certainly be the first step.

plumbum

Sorry I should have mentioned that the fans were working properly.

I will try and bleed the air tomorrow and go from there..I hope that is the only issue. Thanks again for all the replys

kev951

also could be a leaking water pump, introducing air. does the heat come back when revving the engine?

plumbum

Heat will come back when revving the engin and remain for a bit and then go full cold again

kev951

check the bleed screw to see if it is leaking there, put a pressure tester on, pump to about 13psi and check both cold and hot. otherwise, it could be the pump

plumbum

Defiantly not the bleed screw leaking. To be sure I am bleeding the system with the car running from cold?

kev951

bleed with car off, not running. very simple to do, i don't know why everyone makes it soo complicated....take out bleeder screw, fill up coolant resevoir slowly until water starts to stream out of the bleed screw, cap it, start it , turn on heater, if heater takes a while or is not hot , rev engine to about 2500 rpm while quickly cracking open the bleed screw and shutting it few times, back to idle, check heat again. hot now? staying hot? good. done.. not staying hot. ... leak or bad water pump. also make sure the vacuum to the heater valve is good and the check valve on the firewall still works as it should (one way black/blue valve on vacuum lines and make sure your heater valve is in tact.

plumbum

Perfect I will do that tomorrow and see how it goes!

plumbum

Just an update...I bled the system this morning, however I am not confident I was able to get all the air out (Or more is coming in) However I now have proper heat, the gauge still moves between the "Normal" range but no longer creeping up into the hot end.

I was able to go for a 20min drive with no issues.

Thanks again for all the assistance, I still believe I may have an issue and will keep an eye on things. I was already planning on doing the belts/water pump in the summer fall and hope the pump might be the issue.

kev951

dont forget hoses, radiator cleaning, and new thermostat! also if your water temp sensors are original or unkown when last replaced, change them both. blue and black.