Overheating at Idle

Tiny
BCM2004
  • MEMBER
  • 2004 TOYOTA 4RUNNER
  • 4.0L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 260,000 MILES
Dial reads H at a full stop then somewhat goes down upon movement but not by much just lightly below the red.

another issue: A/C blows cool only when vehicle is in motion (starts to blow hot after sitting idle.) Same with heat only blows hot when vehicle is in motion.

What can be the cause of these 2-3 issues?

was thinking thermostat for all of it?

coolants been checked! Radiator seems fine.
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Tuesday, October 12th, 2021 AT 11:43 AM

1 Reply

Tiny
SQM
  • EXPERT
Hello,

It sounds like the cooling fans may not be operating properly.
As when the vehicle is at a standstill there is no/little air going thru the radiator, but as it moves the air flow cools the ending down.
This vehicle has a mechanical cooling fan which is controlled by a fan clutch, the clutch can be defective and not engaging the fan blade.

Take a look at these articles on fan clutch:

https://www.2carpros.com/articles/how-a-clutch-fan-works
https://www.2carpros.com/articles/fan-clutch-symptoms

Another possibility is a bad water pump, as it is unable to circulate coolant thru the engine.

https://www.2carpros.com/articles/symptoms-of-a-bad-water-pump

It is probably not a thermostat as if it were the thermostat stuck closed the temperature would not have changed whether the vehicle is stationary or moving.

Please let me know of any questions.
Thank you.
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Tuesday, October 12th, 2021 AT 12:33 PM

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