Overheating when Idle replaced the thermostat

150,000 MILES • 3.4L • V6 • 4WD • AUTOMATIC
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ZAYTOVEN
  • MEMBER
  • 1 POST
Replaced the thermostat and that does not appear to be the problem. any suggestions?
Apr 5, 2018 at 2:39 AM
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SQM
  • ✓Experienced Mechanic
  • 6,383 POSTS
Hello,

If it only overheats while the vehicle is stationary, it could be due to an inoperative cooling fan.
When the fan does not work, there is little to no air flowing through the radiator. This causes the engine to overheat, but you start to drive air flows through the radiator can cool down the engine.

An inoperative cooling fan can be due to a faulty relay, bad wiring, coolant sensor or a bad fan motor.

First check the relay. There are 2 cooling fan relays. Both are located under the hood fuse box.

Here is a guide on how to test relays:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

If the relay is good make sure there is power to the fan and try providing 12V power to the fan to see if it comes on.
If the fan works manually but does not come on when it is supposed to it could be a wiring issue or a faulty coolant temperature sensor.

https://www.2carpros.com/articles/how-a-coolant-temperature-sensor-works

I have attached diagrams for your reference.

Please let me know if you have any questions.
Thank you.
Dec 18, 2021 at 2:11 PM
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