fbgh2o

This is an update and continued request for help on a cooling issue. I apologize for this post, but no one (including the pros) seems to know what to do.

A special thanks to ehall on all his help with this!

About 10 days ago, the high speed fans came on when the temperature gauge was showing 80C. Additionally, the temperature gauge had been a bit jumpy from time to time (bad grounds -right?). Immediately, I thought that something was up with the gauge. So I cleaned the contacts on the temperature sending unit and also the football shaped connectors on tha back of the instrument pod and presto it was showing 95C to 100C while driving and no more jumping around. The car does not overheat even while idling, just runs hot.

So I have:

1. Flushed the coolant and checked for blockages - none
2. Added water wetter
3. Bled all the air out. I am 99% sure that there is no air in the system - the garage used their vacuum system and also used the nose in the air approach with a pressure tester to verify.
4. Changed the thermostat to an 80C one (after a new 90C seemed to make no difference and I suspected it to be bad)
5. Replaced the thermoswitch to with a new 85C / 93C one
6. Replaced the expansion tank cap
7. Checked for leaks under pressure - there are none and there is no coolant loss
8. Had my garage check for a head gasket leak - there is none

And still it runs at 95C. Is it possible the gauge is reading say 10 to 15C too hot?

That leaves the sender and the gauge. The sender seems to work properly, so before I throw any more money at the problem I am going to test the gauge as per Clark's Garage. I hope it is the gauge - perhaps when I cleaned the "football" in the instrument cluster that I screwed something up? Anyone have any ideas?

Many thanks

lee101315

Measure the temp at the inlet and outlet of the radiator first, see what the temp drop is. Then check the cylinder head and see if it actually is 95C. I had the same problem, my guage indicated my car was close to overheating but the coolant was only 135-160degF where ever I checked it. I changed the temp sensor and that solved the problem.

fbgh2o

Thanks, any suggestions on how to do so?

shiners780

Did you test the expansion tank cap to be sure it holds pressure?

fbgh2o

Yes, forgot to indicate above - new expansion tank cap

2bridges

I think I mentioned from your other thread - the radiator may be funky.

My car with 80K miles always ran warm. Had radiator shop remove tanks, rod out rad core and re-assemble. Despite low mileage - they indicated approximately 20-25% blockage. Afterward car immediately ran cooler

Something for you to consider

porschaholic

Don't know if anyone has already mentioned this but if the battery cables have deteriorated it can cause the gauge to read high. As more electrical demand is placed on the electrical system (Fans on high speed, AC clutch, etc.) the voltage would drop which actually made the gauge read higher. I had this problem with my car and it went away when I replaced the cables.

Dean
'87 951

fbgh2o

Thanks Dean.

I am becoming increasingly a proponent of an electrical issue. I have an IceShark kit enroute as we speak. Seems to run hotter with the accessories on, although the voltmeter actually shows that the charge is good.

I am also going to test the gauge tomorrow to see what it shows. I just got home from the garage and the engine is not even really hot - which leads me to believe that my eyes are being deceived.

2bridges - I have them flush and clean the radiator - they indicated that it was pretty clean and not a lot of scale came. Also the fact that I cleaned the contacts and all a sudden it is running to hot leads me to believe that I screwed something up. Given the cost of a new rad, it will be my last replacement item

anders44

I played with my new oil temp gauge today, and boy, bad ground really makes that thing fly way up

fbgh2o

Thanks Anders... I am inclined to agree, I just idled it for 10 mins... the gauge read 100C and the fans hd not even kicked in - which means it had not got to 85C. The engine was not even really hot.
It seems to be electrical.

ehall

yep. I agree with these guys. You've done everything possible, and some of them a number of times, but the problem is still hear. It's time to look at the accuracy of the guage.

lee101315

You'll need one of those infared temp gauages... its something like a laser you point, and it will tell you the temp of whatever it touches. You can buy them new for 70 bucks, or borrow it from someone.

Papamurphdog

It does sound electrical, but don't forget to review the heater core system. If the core is bad or going bad it will affect temp readings. Happened to my old '87 944 POS...glad that car is dead; it was frigging possessed or sometjhing!

fbgh2o

Thanks for the additional comment on the heater core. The heater seems to work very well right now. How would such an issue manifest itself?

Tom M'Guinn

If you turn the heater on full blast, does the temp come down? That would suggest it really is running hot (rather than a gauge issue).