SCTA99

I have a 1999 trans am with a D1-SC procharger. I have recently ran into an overheating problem it seems like ever since I changed the coolant temp sensor. Whenever I am driving at a constant speed of 60mph or over it doesnt over heat but whenever im just driving around town it will. also whenever I stop at a red light or something it will cool off. but once I start moving again it will rise. any ideas or questions would be great.

98pontiac

how hot does it get? did you get all the air out of the cooling system after you replaced the sensor? You might be over reacting staring at the temp gauge after you replaced the sensor.

waterbug1999

iTrader: (3)

you get all the air out of the lines when you swapped out the sensor?

LS6427

iTrader: (2)

If it started RIGHT after you replaced the sensor, its a good chance the new sensor is bad. But always make sure there's no air in the system, thats a killer.

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SCTA99

Alright, First of all thank you all for your replies. The air in the system would make sense since it seems to have started right after I swapped it. "98 Pontiac" - It will rise almost to 260, then I pull off to the side of the road and wait about 2 minutes start it up and its at around 180. Im curious now though, I left the radiator cap off while it was on an incline with the heater running and thought all the air was bled out but friends have told me I need a special vacuum for the LS engines. an "air lift" system. Is this correct?

THE SHOP

Weird....

LS6427

iTrader: (2)

No, thats incorrect.

You just need to start the engine WHEN COLD with the radiator cap "off" with the coolant topped off. Stand there and wait for the t-stat to open and the coolant starts to flow. If the level drops down IMMEDIATELY top it off. Then wait for the t-stat to close and the flow stops (about 30 seconds). Then wait again.

Make sure that you're not standing there overheating, it'll take about 8-10 minutes to open and flow.

While you're waiting for it to heat up...squeeze the upper and lower radiator hoses rapidly and fully about 20-30times to move the coolant through the system. If the air bubble is rght up against the t-stat on the engine side, it'll push it through by doing this. Then the coolant thats slowly heating up in the heads will reach the t-stat to open it.

If you do that process twice and top it off, you'll be good to go.

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SCTA99

Alright man ill do that, I appreciate the advice. Ill keep you updated with any changes. Thanks again.

LS6427

iTrader: (2)

If that doesn't do the trick, you might have a failing/sticking t-stat that is not opening fully.

Also, a bad radiator cap can cause air to get in slowly over time. It pushes coolant out at very little amounts that you would not hear or smell, then you have that space in the system, which is air.

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THE SHOP

Sure as hell almost sound like head gaskets, so go with air and a new thermostat and let us know.