I have a 99 Sportage with about 60K miles on it. Been having overheating trouble for the past couple of weeks now. While I am working on pinpointing the source of the overheating, I am also concerned that my temp gauge is reading normal (~180 F) when the engine is actually a lot hotter (hot enough to cause piston knock or ping:eek: ).

The interesting thing is when I turn the heater on, the temperature gauge needle moves to show a higher temp. When I turn the heater off, the temp gauge needle goes back down to normal.

I don't really know how to address this type of electrical problem. Any ideas on how to test to see if I have a bad ground somewhere?

Also, any knowledge of where the temperature sensor for the engine is would be helpful.

I have a 99 Sportage with about 60K miles on it. Been having overheating trouble for the past couple of weeks now. While I am working on pinpointing the source of the overheating, I am also concerned that my temp gauge is reading normal (~180 F) when the engine is actually a lot hotter (hot enough to cause piston knock or ping:eek: ).

The interesting thing is when I turn the heater on, the temperature gauge needle moves to show a higher temp. When I turn the heater off, the temp gauge needle goes back down to normal.

I don't really know how to address this type of electrical problem. Any ideas on how to test to see if I have a bad ground somewhere?

Also, any knowledge of where the temperature sensor for the engine is would be helpful.

The temp sensor for the computer is different for the one for the guage. They are both mounted to the Tstat housing at the front of the engine.

Temp guages are not always accurate.

Coolant leaks you want to look for are the heater pipe oring beneath the alternator, Tstat gasket leaks, hoses of course and I have seen a few cracked blocks on the drivers side beneath the manifold but it is rare.

Any air in the cooling system throws off the sensors.

Changes in the indicated temperature when heater blower is turned on - and varying with the blower setting - is a common complaint and can be traced mostly to some faulty grounding or wiring problem - corroded ground at the engine block and the like, so in itself this is not an overheat problem.
I'd check ground voltage on sensor ground wire, like the yel/green wire at temperature sensor : voltage should be zero or a very small voltage, like 0.1 volt, and not increase when you turn blower on or any other accessory. Engine does not have to run when you do that test but ingition key to ON so blower/wipers/power windows can run.
www.geocities.com/lmp4203/kiasport/tempsenders.jpg
www.geocities.com/lmp4203/kiasport/sensors.jpg