Overheating...AGAIN!

[131]

I am surprised the fan did not come on at 240.

The temp sensor is in the head, the fan switch is in the bottom of the radiator, depending on the problem, the bottom of the radiator can be cold as the engine boils.

[blazingspider]

If you are sucking air into the cooling system from somewhere, even if it's just a little bit each time you run the car as in my case with the heater valve, eventually you will get enough air in there to prevent the external thermostat from opening.

If the thermostat doesn't open, the lower portion of the radiator never gets hot enough for the fan switch to close the circuit and the fan will never come on. If you jumper the fan to run all the time and you still have air in the system preventing the thermostat from opening, you are still going to have problems with higher temps.

Good luck!!

[pwilliam]

I agree about jumping the fan so I decided not to do it, although I have never experienced the lower radiator hose not getting hot. The stat seems to always open and have full confidence that it is functioning properly.

At any rate, I came home two days ago and the flush t was almost completely full. Ran the car for half an hour or so at idle and the fan kicked on at regular intervals, running for a consistent amounts of time and always coming on around 210. Was somewhat pleased by this because prior to that evening the fan would only sputter for a few seconds and shut off, come on again a few seconds later, sputter some more and stop.

When I got home last night I decided to check the flush t and it was completely full, coolant dribbled out when I took the cap off. I had not added any coolant the previous night, so it seemed to suck it back in from the expansion tank, but where did the air go? I ran the car for about an hour last night while I washed it, I later took it for a drive and the fan kicked on at regular intervals, still coming on around 210 but always bringing the temp down to about 190-195. So I decided to check the temp of the thermal sensor for the fan. It would activate around 195 and deactivate around 185...sounds pretty normal. This lead me to believe I was having an electrical issue with the temp gage, which I have yet to investigate.

This morning I thought I might drive the car into work but decided to check the flush to before I headed out and there was air back inside again, so I left her at home. The inconsistency of the coolant level is really throwing me, as is the fact that the fan would not work properly and it is now working properly without having any changes performed to the system.

Have yet had time to bypass the heater core, going to try that when I get home tonight if its still sunny out. Hopefully I can report back tomorrow with some more conclusive updates. Thanks for all the great tips and suggestions.

[4uall]

[pwilliam]

Evil little bastards! I got a good laugh outa that. Thanks!

[TX82FIAT]

The heater core bypass is pretty easy to do and if the hoses are good you can buy a brass fitting at lowes or home depot to connect the two hoses in about five minutes. electrical gremlins will absolutley effect what your temp gauge reads. I still get a kick out of my temp gauge going up five degrees the second i turn on my headlights.

[wmbrabrand82spider]

This has been the most difficult "Gremlin" for me as well. 82 Auto newly rebuilt trans and engine. Tstat boil test - ok, burped system three times now, grounded fan and it is working fine. Sensor comes on and fan starts about 205 and seems to run an appropriate amount of time. Problem I am having... and I do not know how to fix it... the top two radiator hoses are bulging like they are going to explode. New from IAP, but very worried, it can not be normal. Temp is good, fan comes on, on leaks, Tstat drilled, heater core bypassed, Bleeding "T" installed.... hoses are jacked. Ideas???? Faulty hoses? Pressure seems very high.

[4uall]

I meant to post this sooner

http://www.mirafiori.com/faq/content/co ... lbleed.htm

and for those worried about high temps, they could always invest in one of these

http://www.autoricambi.us/product/CO2-0 ... -1979-85-/