Engine lightly overheating with A/C on

[paulcmartin]

During a trip to the desert with the ac on...my truck went to 270 degrees. I shut the ac off and it went right down to operating temp and held steady. I flushed the coolant system and no problems for 5000 miles. Now my truck is going from 210 (operating temp) to 220 then it will go to 210 and back again to 220. This is only when my ac is on. My guess is the thermostat. Before I pull the alternator, can anyone confirm my theory.?

 

[Tiggerr]

Id check the fan clutch. Sounds like it's not engaging the fan when ac is on. Check your condenser and radiator too make sure your not all blocked up with bugs/dirt/debris. Thermostat sounds fine to me.

 

[Mooseman]

Search for my thread on how to test the electro-viscous fan clutch. Sounds like your problem.

 

[BlazingTrails]

It may also be a good idea to check the temp sensor. I kinda doubt it was really at 270 deg, at that point you would have likely experienced a head gasket failure, or stall out. Do you have access to an infrared thermometer? If so that would be a tell all if you were actually over heating that bad or a sensor failure. Did your coolant boil out?

Also are you basing your temp measurements on the gauge cluster only? If so you really need to check it with a scanner or ELM 327 or something of the like.

 

[paulcmartin]

I was on the road., so I was checking only by cluster gauge. Once I got to a shop I had them swap the coolant, the old stuff looked like it was pretty old. Then it went away for a while. So that's why I don't think it was a sensor. But it could be

 

[paulcmartin]

Thanks mooseman. Just watched the video you posted. I'll check that next and I'll check for wobble in the bearing

 

[paulcmartin]

Checked the fan clutch. It's working correctly

 

[gmcman]

It may also be a good idea to check the temp sensor. I kinda doubt it was really at 270 deg, at that point you would have likely experienced a head gasket failure, or stall out. Do you have access to an infrared thermometer? If so that would be a tell all if you were actually over heating that bad or a sensor failure. Did your coolant boil out?

Also are you basing your temp measurements on the gauge cluster only? If so you really need to check it with a scanner or ELM 327 or something of the like.

Yeah, 270 deg with an aluminum head is not a good thing. Definitely check the fan and your coolant level. If you did develop a head gasket leak then you can get air bubbles in the coolant causing overheating. That's an almost worst case scenario but something to keep in mind.

 

[HARDTRAILZ]

I would not trust the dash gauge at all.

 

[triz]

Slow water pump failure. I hate cheap water pumps. I'm on my third one. This one lasted two years.

But anyway sorry for the thread drift, check around the fan clutch. Are you smelling coolant at all? I could not see coolant around mine for a bit till this weekend when I decided to change it. Temps are back to normal.