: Temp gauge issue (Question 2)



bradskie
05-31-06, 07:16 AM
As of three days ago my temp gauge is now running between straight up and 3/4 mark. I've had this car since 2001 and temp gauge has never went past straight up position. Its a 2000 deville with 90k miles. It began running rough when first started until I blow out what is in the cylinders. I was thinking it may be a leaky injector but now I think it may be related to a head gasket leak? (is that possible) If I am on the expressway straight up position but in regular traffic it runs hot. I noticed both electric fans run only when AC is on but when I turn the AC off the fans never run. Should the electric fans run when the engine running hot or when the engine is shut off and is hot? Could I be blowing combustion heat into a coolant passage making the engine run hotter?

codewize
05-31-06, 07:57 AM
As far as I know the fans should come on when the temp reaches a certain threshold. There are 2 fans as you stated one is the engine cooling fan and the other is noted as the 'Auxiliary' cooling fan. The auxiliary cooling fan will run anytime the AC is on. When the car reaches a certain temp, both fans should run. I don't know what that temp is but it sounds like there is a sensor problem somewhere.

bradskie
05-31-06, 08:53 AM
Unless I turn the AC on neither fan runs even when running hot. Its either both fans on or both fans off. The car still runs hot with the AC on and both fans running.

JimD
05-31-06, 09:09 AM
As of three days ago my temp gauge is now running between straight up and 3/4 mark. I've had this car since 2001 and temp gauge has never went past straight up position. Its a 2000 deville with 90k miles. It began running rough when first started until I blow out what is in the cylinders. I was thinking it may be a leaky injector but now I think it may be related to a head gasket leak? (is that possible) If I am on the expressway straight up position but in regular traffic it runs hot. I noticed both electric fans run only when AC is on but when I turn the AC off the fans never run. Should the electric fans run when the engine running hot or when the engine is shut off and is hot? Could I be blowing combustion heat into a coolant passage making the engine run hotter?

If you are not losing coolant there is not likely a head gasket issue.

Does the coolant temp. run a little beyond vertical with A/C ON in stop and go traffic?

With A/C OFF, both fans are commanded ON at low fan speed (the fans are powered in series) at approximately 223 degrees and go off at approximately 210 degrees. You will not hear the fans running, you must visually observe. You should be able to see the fans cycle on and off on a warm day with the engine at idle and no breeze or air movement over the radiator.

With A/C ON, both fans are commanded ON at high fan speed (both fan motors connected to 12 volts) continously as you have observed.

You may have something as simple as a faulty coolant temp. sensor sending bad information to the PCM. Or possibly a failed fan control relay.

Ranger
05-31-06, 09:14 PM
As of three days ago my temp gauge is now running between straight up and 3/4 mark. I've had this car since 2001 and temp gauge has never went past straight up position. Its a 2000 deville with 90k miles. It began running rough when first started until I blow out what is in the cylinders. I was thinking it may be a leaky injector but now I think it may be related to a head gasket leak? (is that possible) If I am on the expressway straight up position but in regular traffic it runs hot. I noticed both electric fans run only when AC is on but when I turn the AC off the fans never run. Should the electric fans run when the engine running hot or when the engine is shut off and is hot? Could I be blowing combustion heat into a coolant passage making the engine run hotter?
Yes, that is possible. A cylinder pressure test will confirm or rule it out.