Engine overheating when A/C is on

WHITE4ACTUAL

MEMBER
2008 CHEVROLET IMPALA
3.5L
6 CYL
2WD
AUTOMATIC
127,000 MILES

My car goes into the red and a warning come on saying engine hot turn off A/C. I replaced the thermostat, coolant temperature sensor, water pump, and flushed the radiator with blue devil radiator cleaner. I've bleed the coolant and made sure the overflow tank is at the correct level. The radiator fans work as they should as well as the ac fan. The heat works fine and the car only overheats while the a/c is running. I've also checked to make sure the head gasket is not leaking by testing the coolant with the special blue liquid tester thing and that passed as well. Not leaking coolant anywhere. I'm thinking it's the ac compressor but was trying to figure out if I have overlooked anything before I shell out a few hundred dollars.

2 Replies

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

When this happens, other than the temperature gauge indication it is over heating, are there other indications? For example, is there coolant overflowing or steaming under the hood?

Also, when this happens, inspect the radiator hoses. Make sure the lower one in particular isn't collapsed.

Let me know.

Joe

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Friday, June 5th, 2020 AT 8:26 AM

KASEKENNY

MECHANIC
18,907 POSTS

Interesting that you mentioned the compressor at the end of your post because as I was reading it, that is just where my mind went.

Does the compressor cycle on and off or does it seem like it remains on for a long time or not cycle off at all? If it does not cycle the that is the issue. If it is cycling, we need to make sure the radiator is not face plugged blocking the air to come through. However, if shutting the A/C off allows the engine to cool, I would just go ahead and replace the compressor.

In other words, if the engine never overheats with the A/C off and when the A/C is on and it starts to overheat, if shutting it off allows the engine to come back to proper temp then the compressor is the issue.

I included the process on the compressor replacement and oil balancing procedure if you decide to go with it.

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