skibuggy

Background. Replaced coolant, tstat, temp sensor and MFS within the last year. yesterday the coolant temp gauge moved passed its normal spot. It was solid at the second small dot to the left of the "H". I was at our destination already so parked the car and went skiing. Four hours later I got back started the car. It went to the same second dot by the time I pulled out of the parking lot. I stopped at a gas station 5 miles down the road to check under the hood. When the gauge was still at this second dot, I opened the coolant reservoir cap and it was not bubbling nor steaming. Everything seemed to be running just right. I am thinking a temp sensor, right? How would I check to see if that is the case before throwing new parts on the car? by the way the red warning light did not come on initially. It did come on about 30 miles down the road. I pullled over again and check the cap and everything seemed fine in the reservoir.

thanks
Cenk

audiqv8

Try turning the heat up to HI and see if the temperature goes down. Could be a stuck thermostat; turning the heat to HI will cause the heater core to act as a mini radiator and keep the engine coolant from overheating.

You could also verify that the thermostat is working by carefully touching the radiator hose once the engine get up to temperature; but be very careful it will be very very hot if the thermostat is working properly.

skibuggy

I will check that. But if the tstat was closed I would not get any heat in the cabin right? Because I can get it quite toasty inside the car right now.

audiqv8

"But if the tstat was closed I would not get any heat in the cabin right? Because I can get it quite toasty inside the car right now."

Nope, The heater uses the coolant within the block, which is why you should turn the heater to HI if the thermostat fail (closed) or if the radiator is clogged. If the engine runs normal with the heater set to HI (no overheating) then I would check the thermostat and also the radiator.

skibuggy

checked no difference in temp gauge with the heat on or off. The upper rad hose is hot. Does this pretty much rules out tstat as the culprit?

audiqv8

Yep this mean that the thermostat is working. Now carefully check the bottom radiator hose, it should also be hot. if it isn't then you most likely have a clogged radiator.

BTW is the radiator fan working when it starts to overheat?

audiqv8

Yep this mean that the thermostat is working. Now carefully check the bottom radiator hose, it should also be very hot. if it isn't then you most likely have a clogged radiator.

BTW is the radiator fan working when it starts to overheat?

skibuggy

The aux fan does not come on when the temp gauge is on the hot side. Now the aux fan will come on at other times. but it is not tied to the needle passing a certain point. That is why I keep thinking false readings at the gauge. I might be jumping ahead of me.

audiqv8

"The aux fan does not come on when the temp gauge is on the hot side."

This is a problem. Does the fan only runs when the AC is on?

Does the car overheat while driving on the highway? Does the car overheat while idling or in stop and go traffic? Did you ever get a chance to check the lower radiator hose?

skibuggy

just not necessarily when the car is on the hot side. The car has not been running hot since the first occurance. It is running closer to the middle of the gauge, rather than between the first two thick marks, where it used prior to last weekend.