Overheating

[David Barnes]

2007 Yukon Denali with 6.2. It runs great on the highway. Get on the city road and it starts overheating. Replaced the water pump and thermostat about 3 months ago. The radiator cores are clean. Can someone please tell me what is going on? Could it be the fans aren’t working right or the radiator cap could be bad?

 

[Shaggy]

2007 Yukon Denali with 6.2. It runs great on the highway. Get on the city road and it starts overheating. Replaced the water pump and thermostat about 3 months ago. The radiator cores are clean. Can someone please tell me what is going on? Could it be the fans aren’t working right or the radiator cap could be bad?

Moved to correct location.

 

[Kraig]

My bet is on fans—at highway speed you generate the airflow to remove heat from the radiator and in town you don’t.

 

[Doubeleive]

Pretty easy to verify if it is the fans or not as soon as the temp goes up from dead center then pull over and pop the hood and see if the fans are running or not, if they are then that's probably not the issue, if they are not running check relays and fuses first and proceed from there.

 

[petethepug]

One thing that needs to be verified is if you’ve got an air bubble in there. Grab a beer, coffee or whatever and let the motor come up to temp with the cap off the coolant tank. It will burp out if they’re in there.

DO NOT leave baby unattended. If the motor is ailing something else and runs hot while ur away, ur skewed. You only have to do this correctly once. After burped, it’s cured or move on to the next diagnosis.


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[BG1988]

2007 Yukon Denali with 6.2. It runs great on the highway. Get on the city road and it starts overheating. Replaced the water pump and thermostat about 3 months ago. The radiator cores are clean. Can someone please tell me what is going on? Could it be the fans aren’t working right or the radiator cap could be bad?

check the fan fuses


the rad cap can be worn out or gummed up and stuck open

 

[thompsoj22]

I bet fans also, High/low fan speed relays in the engine fuse box. look under the lid and it will define their location. it may just be one or the other, as stated above start the engine from a cool temp and watch the fans, low speed should turn on first, if it does than turn on ac max and high speed should cycle on next. if low never turns on than start with that relay or vice versa. if both fans function correctly and if you have done any coolant flushes than air in the system is a consideration. also simply swap the relays to confirm the bad relay and not a fan motor.