Overheating at idle

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May 17, 2026 | 05:06 PM

Q1king

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Teching In

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Overheating at idle

Hi all,

I recently bought a ’97 Trans Am, and it’s been running fine overall. I replaced the thermostat, flushed and refilled the coolant, and properly bled the system. However, it has started overheating at idle or when stopped at a light. On the highway, it stays at normal operating temperature with no issues.

This just started today. It’s about 90F outside, and every other time I've driven it, it's been a cooler day.

Any help or advice is appreciated.

May 18, 2026 | 08:33 AM

shbox

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Joined: Dec 2008

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From: Little Rock, AR

Define what you call overheating. Have you used a scanner to look at PCM reported temps and checked for fan operation when they are commanded on?

http://shbox.com/1/4th_gen_tech2.html#cooling

May 18, 2026 | 08:59 AM

Q1king

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So the PCM reports back 106c/223f. The gauge shows that it's close to the red zone.

May 18, 2026 | 12:20 PM

irocbsa

Staging Lane

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Joined: Mar 2006

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From: Ann Arbor, MI

223F is perfectly normal while sitting and idling on a hot day. The sending unit, wiring, or the gauge itself might be failing. The sending unit is on the driver's cylinder head between #1 and #3.

May 18, 2026 | 12:40 PM

Q1king

Thread Starter

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Yeah I think it might be the sending unit. I'll swap that and report back.

May 19, 2026 | 08:21 AM

shbox

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Joined: Dec 2008

Posts: 4,147

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From: Little Rock, AR

I don't see any problem. If it gets above the threshold for the fans to come (226°) on and they don't, then there is an issue. The gauge seems to be acting normal for this car.