Overheating when AC is on.

Vonhendon

Original poster
Member
Dec 7, 2011
55
Envoy run's one tick below 210 deg. when AC isn't on but once it's on it goes up 3 tick's above 210 deg. before I started having problem's last summer it always stayed at 210deg. Had a shop look at it more then once last year and they changed my T Stat to one that I didn't want. They said it could be my Rad. but my question is I don't have a prob. until the AC is on. At highway speed's it does come down a little but in traffic I get very nerve's so I plan on changing the Rad.
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RayVoy

Member
Nov 20, 2011
939
The AC blows cold in the cabin, but produces heat under the hood. The condenser is mounted in front of the radiator and is cooled by the same air flowing through the radiator. When AC is off, the air hitting the rad is outside air temp, when the AC is on, the air hitting the rad has been warmed by the condenser and is now much hotter than the outside air. This is not usually a problem, if you have good air flow.

Two things, the air flow may be blocked and/or the engine fan may not be turning.

You may be able to blow the debris out of the rad by blowing compressed air from the engine side.

The fan clutch may be shot, or the temp sensor (that locks the fan clutch) may not be working correctly.
 

Sparky

Member
Dec 4, 2011
12,927
I'd clean the radiator/condenser/etc

Radiators don't just go bad though, they're a hunk of metal with water passages and fins. Unless it springs a leak it doesn't need replaced, but you might have some blocked passages. Run some radiator flush through it. I had to flush the radiator on my old car but it was perfect after that.

But in stopped traffic you'll see some increase. Not sure what the actual temp is at 2-3 ticks above the 210 mark on the gauge, but it may not be as hot as you think. Got a scan tool?
 

Vonhendon

Original poster
Member
Dec 7, 2011
55
Sparky said:
I'd clean the radiator/condenser/etc

Radiators don't just go bad though, they're a hunk of metal with water passages and fins. Unless it springs a leak it doesn't need replaced, but you might have some blocked passages. Run some radiator flush through it. I had to flush the radiator on my old car but it was perfect after that.

But in stopped traffic you'll see some increase. Not sure what the actual temp is at 2-3 ticks above the 210 mark on the gauge, but it may not be as hot as you think. Got a scan tool?

I know I don't have any debris blocking the condenser or Rad. T stat was changed last year but not the ECT. Maybe I'll try the flush before getting a new Rad. I was told last summer by the stealership that my fan clutch turned about 400rpm slower then normal. Is a Murray Rad. from O'Reilly pretty good?
 

shrek77

Member
Mar 30, 2012
252
My 05 did the same thing last summer. It was the fan clutch . It always spun fast enough to keep it cool in traffic without ac, but with the AC on sitting in traffic it would start going to just past 3/4.
 

Mypetropig

Member
Dec 29, 2011
226
If your fan clutch is already turning slower than normal/commanded speed that problem will be amplified by turning the a/c on, which is supposed to increase fan speed. I would consider replacing the fan clutch. I am not sure of the exact RPM but if the PCM is commanding a certain speed and the clutch cant keep up then the CEL should come on.
 

Sparky

Member
Dec 4, 2011
12,927
If the fan clutch is spinning slower than it should be I'd replace it before the radiator. There isn't much that can go wrong with a radiator but a bad fan clutch isn't all that uncommon.
 

c good

Member
Dec 8, 2011
547
If the fan clutch is original, that's probably the problem. Also, there is a software reflash update that addresses low fan speeds causing overheating problems. If you've never had it updated it would be a good place to start. HTH c good
 

IComeInPeace

Member
Jun 21, 2013
9
Vonhendon said:
Envoy run's one tick below 210 deg. when AC isn't on but once it's on it goes up 3 tick's above 210 deg. before I started having problem's last summer it always stayed at 210deg. Had a shop look at it more then once last year and they changed my T Stat to one that I didn't want. They said it could be my Rad. but my question is I don't have a prob. until the AC is on. At highway speed's it does come down a little but in traffic I get very nerve's so I plan on changing the Rad.
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A few years ago, my Lexus was doing something similar. I noticed one day coming home from work, on a pretty hot summer day, the temperature needle was approaching the red. Since I was on an expressway where I couldn't pull off/over, I quickly turned off the a/c and turned the heater on high. Drove her home that way.

I screwed around with that car until summer was over--meaning, I flushed the radiator, changed the radiator cap, replaced the thermostat, etc. No change.

I later decided to remove the fan shroud, and open up the front grill. Then, I took an air gun and thoroughly blew out the condenser coil and radiator. Put everything back together, and ran the car under the conditions that was causing it to overheat (not literally). Nothing. In fact, the car never ran cooler. And, I never had another temperature problem again.

I know the Envoy and Lexus are so dissimilar, it's like comparing apples to oranges. Nevertheless, I thought I'd share my experience anyway.
 

Vonhendon

Original poster
Member
Dec 7, 2011
55
c good said:
If the fan clutch is original, that's probably the problem. Also, there is a software reflash update that addresses low fan speeds causing overheating problems. If you've never had it updated it would be a good place to start. HTH c good

Fan Clutch was changed in 5/10 when I got the (ROAR) I remember it was a very stressful time in my life and I needed my vehicle so a local shop really stuck it to me :redface: I had 152K at that time. Last June is when the overheating prob. began at 179k but after spending $ at different shop's and them finding no real issue's except to say it's been a very hot summer I gave up, but it's AC weather again and my temp gauge want's to go 3/4 and I'm not dealing with this no more. So I'm going to try the Rad. Flush and if that don't fix it maybe a new fan clutch. The clutch that I have has been reflashed. where can I get a good fan clutch for a decent price?
 

MrFrodo

Member
Apr 13, 2012
9
Is 2-3 ticks above the 210 mark really an issue though? I mean it's nowhere close to the red mark on the far right. It hit 107F here in Houston on Saturday, and I was stuck in traffic for about 45 minutes. My gauge got up to 3 ticks above 210, but I assume it was just a combination of sitting in traffic with the A/C going on a very hot day. The next day in normal driving it didn't get above the 210 mark though.
 

DocBrown

Member
Dec 8, 2011
501
With the right scan tool the shop should be able to test the speed control commands for the fan clutch. Chances are its bad again. I just replaced my fan clutch the second time. A bad fan clutch will also cause a high pressure issue with the A/C.
 

Sparky

Member
Dec 4, 2011
12,927
MrFrodo said:
Is 2-3 ticks above the 210 mark really an issue though? I mean it's nowhere close to the red mark on the far right. It hit 107F here in Houston on Saturday, and I was stuck in traffic for about 45 minutes. My gauge got up to 3 ticks above 210, but I assume it was just a combination of sitting in traffic with the A/C going on a very hot day. The next day in normal driving it didn't get above the 210 mark though.

I don't think it is, mine does edge up a couple ticks if sitting in traffic in hot weather and the AC blasting. Like you said, it isn't anywhere near the red mark.
 

Vonhendon

Original poster
Member
Dec 7, 2011
55
MrFrodo said:
Is 2-3 ticks above the 210 mark really an issue though? I mean it's nowhere close to the red mark on the far right. It hit 107F here in Houston on Saturday, and I was stuck in traffic for about 45 minutes. My gauge got up to 3 ticks above 210, but I assume it was just a combination of sitting in traffic with the A/C going on a very hot day. The next day in normal driving it didn't get above the 210 mark though.

It's a problem if it's 85deg. and your moving about 30mph. Where can I buy a quality clutch fan at a decent price, I'll never let a garage put one in for me again.
 

Sparky

Member
Dec 4, 2011
12,927
Rock Auto has a lot. I'm not sure about which brands are the best though. Supposedly the Dorman was an updated design, but I think some people have had some issues with those... I guess stick with the newest AC Delco model?
 

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