Gradually Overheat at Idle with AC On

[ChasingHeat]

Hello everyone. I am new here. I have a problem I've been chasing for quite some time. My 2004 Chevrolet Suburban 1500 5.3 liter V8 (original owner) will gradually overheat at idle with the AC on in the Texas heat. I've taken it to several mechanics with no luck. My next stop is the dealer as a last resort.

 

Here is the scenario I can drive my Suburban with the AC on through streets or on the freeway and the temperature never gets above 210 on the dash. However if I pull into a drive-thru that has a long line or if its parked idling with the AC on for about 20 minutes the temperature will begin to rise and if I do not turn off the AC, rev the engine to above 1100 RPM for a bit, or shut off the engine it will eventually hit 260. With the AC off under the same conditions I can let it idle for hours and it never goes above 210 on the dash, even in 100-plus degree weather.

 

I've changed the following components. Radiator, fan clutch(twice, first after market and later AC Delco), thermostat (installed cooler 165 degree thermostat), water pump, temperature sensor, AC compressor pully belt. All current components are AC Delco from the dealer. The upper and lower fan shroud is original OEM and in good condition. The fax blades are in good condition with no knicks or cracks. The serpentine belt looks to be in good condition. I cannot hear it slipping when driving or revving the engine. I've had the coolant flushed at a shop twice. Its not losing coolant or oil and not blowing smoke out the tailpipe so I have ruled out blown head gaskets. Otherwise it would be overheating all of the time.

 

I read somewhere the issue may be the compressor (original) causing too much drag on the engine, causing the engine to work harder than it should at idle, resulting in overheating.

 

I am open to any suggestions or ideas you guys may have.

 

Thank you so much!

[txab]

A few things off the top of my head...

 

Have you double checked the temps you're seeing on the gauge?

 

Are the side panels in place on either side of radiator.? These help direct air to condenser/radiator.

 

Have you checked the condenser for plugging. If it's blocked, airflow through your radiator is diminished

 

When you replaced radiator, did you go back with same size or install something larger with more rows of tubes, increasing the cooling capacity?

 

 

Edit:

You might want to follow this thread too.

 

https://www.gm-trucks.com/forums/topic/241011-04-sierra-engine-cooling-assistance/?tab=comments#comment-2436539

 

 

Edited July 17, 2020 by txab

[davester]

It's my understanding that the ecm is informed when the a/c compressor is enabled, and speeds up the engine a bit to compensate for it (or notices when it's enabled that the engine slows down a bit, and speeds it back up to the right idle speed).

 

Maybe you could try using an IR gun to check that you are getting good flow through the radiator (that it's getting as hot at the engine), and perhaps a laser tachometer and put the reflective tape on the fan to check it's speed relative to engine rpm.

[Colossus]

Heater core could also be plugged preventing good circulation throughout the cooling system? 

[diyer2]

I would check the temperature gauge as mentioned.

The heater core maybe the problem. Remove the hoses from the heater core and using a hose check for flow through the heater core. 

[JHEAD92]

Hey Heatchaser sounds like you've covered alot of ground but I can tell you from experience that replacing AC compressor didn't help my overheating issue. I recently replaced water pump, fan clutch, radiator, thermostat, hoses, belts, pulleys, everything except condenser and heater core. The condenser will be my next step though. Right now I'm battling ebcm faults. Good luck and post a fix if you find it.

[bg1988]

Clean the A/C condenser   that is the solution to your overheating problem ..... bet its clogged with varies insects  

be gentile  I use a toothbrush and  dawn dish soap(just a drop is good enough)  in a squirt bottle  distilled water is preferred if you don't want deposits left behind

I can stick my hand through the grille though but you can remove yours though

 

I clean mine every 6 months  can't risk overheating an aluminum block..anyways

 

my A/C gets cold quickly with in 15 seconds it's all ready blowing cold air

 

  Remote start by the time i get inside it's all ready cooled off..

Edited July 23, 2020 by bg1988

[JHEAD92]

Thanks bg1988 I'll give it a shot.

[Silverado/Sierra guy]

If you are planning on keeping your truck for along time you might want to consider installing electric fans. I put some on my 02 Silverado 5.3, together with a larger radiator and a higher voltage alternator.  It can idle all day in 95 degree Florida weather and not pass 200 degrees.

[tlaw91]

When you replaced the water pump with an OEM one did you get the updated thermostat housing part number? They’re different sizes so if you install a old model thermostat housing with a updated water pump you may have issues.
Just a thought


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[sefiroxx]

Welcome aboard, I have a 04 GMC Sierra, 4.8, with similar problems in the DFW area.
- be sure the purge lines are flowing. One connects the radiator to the top of the surge tank. The other connects the driver side head, thru the throttle body, to the radiator.
- clean the condensor with a hard spray, then soak with a hvac coil cleaner
- the fan blades, while looking good, have weakened and are likely not holding shape with speed

[Earlofcrankcase]

I have a 2003 5.3 Silverado with the same. " lt only overheats at idle when the ac is on" problem. But l believe l may have fixed mine for next to nothing. When l looked at the front of the radiator behind the AC condenser. I could see a mat of debris dead center in front of the fan and almost the same diameter. I took the fan shroud off and blew it out with compressed air. 1st straight down from between the radiator, & condenser. And the from the fan side of the radiator. Keep in mind my air supply is an 80 gallon volume at 140 psi blowing through a non osha approved sprayer with a 6" x 1/8" barrel. There was genuine need to be careful to not blow cooling fins flat, but when the air finally cleared. l took it for a test idle and it never did get over it's just under 200f normal running temp. Now the ambient temp was only 90 f by then but that had been hot enough to cause the problem in the past.

[Earlofcrankcase]

Fixed! Problem is gone. Not much of a pic but that's what caused my overheating problem. Today is was only 91f but I  put it through a lot of drive though type testing and the problem is definitely gone.

[redvett]

Go back to the OEM thermostat 187F the 165F will not help cooling as the coolant temp at 195F the 187F thermostat is wide open. The 165F stat will cause added fueling and lower fuel economy since the PCM sees the engine as running cold.

I suspect an air flow problem such as debris in the condenser or between the radiator and condenser or the water pump is a poor aftermarket.

I live in AZ and summer temps get to 118F and my 04 with 260000+ miles never overheats and i run the OEM thermostat 187F.

[ChasingHeat]

Hello everyone. I wanted to update everyone on my progress. I had pretty much given up on finding the source of the overheating issues at idle. Until recently. My A/C cooling became less and less efficient. Until the cooling stopped all together. Took my Suburban to an A/C shop. Found a slow leak at the high side service port. All 134A eventually leaked out. Had this repaired and properly charged. Now the A/C is blowing ice cold again, front and rear. I can now sit at idle for hours with A/C on and the needle doesn't go past 210. The AC shop mentioned a low refrigerant level can cause overheating at idle with A/C on, due to the compressor overworking trying to cool, generating excess engine heat. Funny thing is I had the refrigerant levels checked by a local mechanic back when I initially created this post. Said all was good. Probably didn't hook up a gauge set to check low and high side pressures. It's going to get very hot here in Texas soon. I will update everyone on the status. Thank you to everyone who offered up suggestions.