100 miles into the trip it started to run hotter?

JAMESLEE1973

MEMBER
1992 FORD BRONCO
V8
4WD
AUTOMATIC
152,000 MILES

I just replaced the thermostat and it is in the right way. On my way to work it ran in the normal most of the way. About 100 miles into the trip it started to run hotter. It would go from the o all the way to the l on the normal scale. While driving at speed it is fine, once you stop the temp begins to climb. I stopped to look under the hood and it was hot but did not seem like it was over heating. The gauge never went past the L. Any clue to what the problem might be.

1 Reply

SQM

MECHANIC
6,383 POSTS

Hello,

It sounds like you might have a faulty radiator fan/clutch. As you mentioned that engine only overheats when you are at a stop. Which means the fan is not blowing air thru the radiator when you are at stand still, and the temperature rises, but as you start to drive air flow thru the radiator and cools the engine to the normal temperature.

When you have a faulty clutch the fan will not engage properly and lead to a engine overheating.

You can diagnose a faulty clutch.
Start the engine and wait till it reaches normal operating temperature.
Stop engine and using a glove or a cloth to protect the hand, immediately check the effort required to turn the fan. If it requires considerable effort, the coupling is good.
But if you can move it very easily, it indicates the coupling not working properly.

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

I have attached diagrams for your reference.

Please let me know of any questions.

Thank you.

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