Car over heats after first drive and then runs cool for awhile

[Rafael]

Here is my problem. My car will overheat right after starting and running for the first time. The Temp gauge will go all the way up to the H and then very quickly drop and run in the normal range on the temp. gauge. After doing some stop and go driving I will see the temp start to rise and drop on the temp. gauge.

So far I have changed the radiator due to a leak, water pump, thermostat, and just recently the fan clutch. I still have this problem could it be air in the system. I need help because now I have run out of things to change and will probably need to take it to the shop and don't want to get screwed for any easy fix I could have done myself.Thanks,Rafael

[Mayhem_J30]

does the 240 have a seperate temp sensor for the gauges? maybe that's going bad.

[Rafael]

I think it does have a seperate temp. sensor but the car is getting hot the water sometimes boils out of the overflow tank. So I do know it is getting hot

[Rafael]

Sorry I forgot to mention this is on a 91 240 SX with about 165,000 miles on the motor.

[erich]

I've had this happen to my car. It was air trapped in the system causing no circulation. You can tell if there is good circulation of coolant by turning the heat on full blast. If there is little or no heat when the temperature is spiking there is no circulation. I got rid of it by installing one of those cheap radiator flush kits inline with the heater hoses and flushing it for a while with the engine running, then draning the radiator and filling with antifreeze. Seems to get the air bubbles out.

erich

[MaineExport]

Take out your thermostat and run without... see if it stays cool. Also, you could try boiling the thermostat to make sure it opens.

I had a very similar problem, I replaced my thermostat and still experienced the same problem. Long story short.... I ended up with a new water pump and a pressure-tested radiator just to end up with the SAME problem still. My mechanic re-checked the BRAND NEW THERMOSTAT.... and viola it was defective. So a second new thermostat did the trick.

If your thermostat is the problem.... running it without should keep it cool. If that fails... then you might want to consider testing the compression. You might have a cracked or warped head... or blow head gasket.