Hi,

92 RS 305 TBI with AC & Electric fan. (Fan only runs with AC on)

It's cooling perfectly fine at idle, however at highway speeds the temp slowly climbs past the halfway mark to almost three quarters.

It seems to spike on hills and is very slow to climb back down. No boiling, heat is working...

Just had exhaust work done, the garage also changed the temp sensor...then this problem started.

Not sure if it's a bad sensor or timing....where to start?

 

Ok. Hot on highway not at idle sounds like air damn. Is it still intact? And did they replace the coolant temperature sensor or sender? Sensor for ecm sender for gauge. I've had bad experiences with anything but ac delco on sensors and senders.

The " sensor" they replaced. is it 2 wire or 1?


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Air dam is intact. The sensor they changed was 2 wire near thermostat housing.

 

Do you know why they replaced it?


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That was off topic. Do you have access to an infrared thermometer? If so that could help eliminate dead spots on the radiator.

sometimes if you have a slightly clogged radiator it won't affect idle because your engine isn't under load.

Has your car sat for any amount of time over 2 months? Could have a little rust. Inspect your coolant in both the overflow and radiator.


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The car did sit for a LONG time because the transmission was shot. The coolant is green.

I'll look into a infrared thermometer.

 

That would be your best friend because you could A. Make sure your gauge is right and B. Make sure your radiator isn't the problem.


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Just got the thermo today. Will try to post results tomorrow.