Originally Posted by coupedeville

I have a 1998 STS with the northstar motor with 120,000 miles. The car runs great except for a couple of things. My problem is what everyone else with this car is experiencing it is overheating. It does not do it all the time. I have read all the posts here and on other forums and have some of the same symptoms but not the same as my problem. I drive the car daily. There is no oil in the coolant no coolant in the oil, no white smoke. no coolant leak. I recently flushed the coolant and changed the thermostat. I ordered a northstar waterpump removal tool so Ican check the impeller.
MY PROBLEM-If I leave the heater on at 80 degrees and 3 of 5 blowing, it will not overheat. If the heat is off and the temp gauge jumps I can usually turn the heat on to 90 and to full range of blowing 5 of 5 and the gauge will drop to the normal level. occasionally the gauge will jump from normal to 3/4 to hot and the usual lights come on and tell me to idle the engine. A couple times I was on the freeway and when this occurred it took me a few miles to get to a place to pull off and by the time I got there the temp was going down. When I pull over and give it 10-15 min. to cool down it will go back to the normal temp reading and I can drive another 100 or so miles home with no problems. Can anyone help me here it is driving me crazy. I would take it to the dealer but it does not do it all the time and I don't want to pay them to drive it around and wait for it to overheat or troubleshoot things I have fixed or have already checked. Any suggestions would be greatly appreciated.


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