At idle, engine temp just gets hotter and hotter. Coolant boils over from reservoir when this happens. Fan never kicks on unless I turn on A/C. I have replaced the coolant temperature sensor (to PCM, not temp. guage) but no joy. Ideas?
I think the CTS for the computer feeds the temp gauge on the dash for
98's.Questions:
Ideas: I believe you are hearing things from the reservior, but it might be normal. My SL's would make lots of bubbling noise too.
Remember, if you really believe you have a over heating problem, then you need to get the car professionally looked at. Having had a car over heat once, the engine later failed. Becareful.
later,
tom @
Another thing: Consider replacing the reservoir cap. I replaced mine and saw coolant consumption drop to zero. A bad cap could cause boiling over at the reservoir.
The fan is controlled by software. As long as the CTS is working correctly, the dash gauge, fan, and fuel mixture are all handled by the PCM using that common data source (in late models like my '97). If you connect a scan tool (not just a code reader), you can read the actual temperature the PCM is seeing. As long as that number is less than the spec, some 200 degrees F as I vaguely recall without looking it up, the fan won't come on.
If you're getting actual overheating, not just an instrumentation problem, another possibility is a bad thermostat. I've been stranded more than once with a bad 'stat (not in a Saturn) so I replace them prophylactically whenever the cooling system is drained. The coolant boils over and overheating can warp the block. The other failure mode is the engine running too cool, wasting gas. Either way, I don't trust thermostats.
If it's not overheating on the highway, my first guess would be the reservoir cap.
RK Henry
What RKH said. Or, possibly, a clogged radiator, or a bad temperature sender (there are two) or the fan relay or a blown head gasket ....
Bob
Do the easy and cheap stuff first.
I am assuming that the coolant is clean and at the correct level and that there are no leaks or collapsed hoses. Check coolant rad and air conditioner rad for blockage from dust or dry grass. Wash well with a hose from the back (with engine off). If it is very dirty you may need to remove the rad to clean properly.
Use a temperature gauge to measure the coolant temperature. How you accomplish this will depend on what tools you have available. I would suggest taping a thermometer (under some insulation) touching the upper rad hose near the engine. Start the engine and watch the thermometer and the temp gauge in the dash. As the engine warms up you should see a rapid rise in the rad hose temp when the thermostat opens. I cannot recall at what temp the fan should start but it is quite high (>200F IIRC someone here may give us a more accurate figure or you can do a search on Google groups as this is a frequent thread)
Does the thermometer indicate that the thermostat is functioning properly? Does the engine overheat? When you turn on the AC this should start the fan. Does the engine still overheat or does the running fan cause the dash gauge and thermometer to cool? Does the coolant boil?
Good luck and keep you hands away from the fan.
It overheats only at idle? If so I suspect a blockage in the rad. When you drive down the road and it doesn't overheat its because the flow of coolant is faster and getting by the blockage enough to keep you cool. If it is a stat it would overheat all the time. If your rad cap is bad the coolant would boil over past the resevoir and you would be able to see that. If your system has be open or added to you might have air in the system which could cause incorrect readings from the temp sensor. and overheating...but that would be all the time. The key to your prob is that it only overheats at idle. I say your rad is blocked up.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.