Engine over heating with AC on at low speeds

[92__silverado]

My 2003 tahoe has a strange issue that has stumped me.

When sitting in traffic with the AC on, the temp creeps past 190/210 all the way up to around 230+ At that point if i turn the AC off and turn the heat on it cools back down. It will consistently overheat in traffic with the AC on though.

All coolant has been flushed and replaced twice, replaced with regular green antifreeze. no dexcool.

Water pump and thermostat have been replaced twice in the last year.

Fan clutch was replaced last week with a "severe" duty one.

I am not able to get the truck to overheat without the ac on.
The truck has a trans cooler, according to the RPO codes but I would think it would be able to handle this. Temps have been low 90's to high 90's when this happens.


Any help would be great!

Thanks.

 

[BubsXL]

My 2003 tahoe has a strange issue that has stumped me.

When sitting in traffic with the AC on, the temp creeps past 190/210 all the way up to around 230+ At that point if i turn the AC off and turn the heat on it cools back down. It will consistently overheat in traffic with the AC on though.

All coolant has been flushed and replaced twice, replaced with regular green antifreeze. no dexcool.

Water pump and thermostat have been replaced twice in the last year.

Fan clutch was replaced last week with a "severe" duty one.

I am not able to get the truck to overheat without the ac on.
The truck has a trans cooler, according to the RPO codes but I would think it would be able to handle this. Temps have been low 90's to high 90's when this happens.


Any help would be great!

Thanks.

Mine acted similarly and it was due to a cracked radiator. You might check that.

 

[Gzes]

You live in a hot area? A lot of vehicles get hot when stopped in traffic with ac on full blast but it shouldn't overheat. Might be getting a small clog?

 

[92__silverado]

How can i check a cracked radiator? I don't seem to have a leak.


Live in TN, its the south so we get warm humid summers. But none of my other vehicles have had this issue.

EDIT:

I've also heard of the GM cooling tabs, these were not put back in after my flushes. Anyone using those?

I marked the reservoir where the coolant level is now while the truck is warm, i'll check again in the morning to make sure its higher after the truck has cooled.

 

[BubsXL]

Mine was cracked at the top/side and would not really ever lose any coolant but it would not let the system pressurize. I am in TN also and neither of my Yukons get hot in the summer.

 

[92__silverado]

Think a cracked radiator would cause the tahoe to get hot when the AC wasn't on too?

 

[BubsXL]

Its possible. Will it get hot sitting in traffic with the windows down and AC off?

 

[livingez_123]

Are you relying on the temp gauge or are you boiling over into the overflow?
if you're not boiling over I would check the temp with a mechanical gauge just to be sure.

 

[92__silverado]

Its possible. Will it get hot sitting in traffic with the windows down and AC off?

I have not been able to get it to do that yet. I've been trying for days.

Are you relying on the temp gauge or are you boiling over into the overflow?
if you're not boiling over I would check the temp with a mechanical gauge just to be sure.

Gauge, but I also hooked up an odb2 scan tool, and it confirmed. It go up to around 236 while i was sitting in a parking lot with the AC on.

I've never seen it actually boil into the overflow, I'll keep a look out for that.

 

[92__silverado]

Update:

Took the shroud off the fan today and used a water hose and some degreaser to spray out the radiator from the back side. Did this four times being careful not to bend any fins. Went a head and gave the front of the rad a good wash too as well as the condenser as best I could.

Drove around for about an hour with no AC on, it was about 90 degrees, had no overheating issues. When i got back in to town I turned the AC on and instantly the temperature started to climb.
go to about 215-220 when i cut the AC off.

I stopped with the AC off and the temperature would still not go below 215, revved the engine a bit to get the fan moving, that got it down to about 210, but it would never go below that while i was sitting.

I'm stumped.