Running hot after idling

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Sep 23, 2025 | 08:22 AM

bigbo62

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6th Gear

Joined: Jun 2024

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Running hot after idling

I have a 95 F-150 with the 302. I just rebuild the engine and I'm almost done breaking it in but I've ran into a small issue. After idling the truck for 15 or so minutes the gauge reads about at the "L" normal. When driving it read between the "N" and "O". I made sure to bleed the system by running the truck with the rad cap off and turning the heater on. I know these gauges are not the most accurate but I was just wondering if this was normal.

Sep 23, 2025 | 08:33 AM

jas88

Lead Driver

Joined: Feb 2002

Posts: 7,961

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From: Greater Austin, Texas

No, not normal. First thing I would do is test the accuracy of your gauge with a temp gun on the thermostat housing. If indeed it is running that hot idling, then you are not getting enough air thru the radiator via the fan. Check your fan clutch.

Sep 23, 2025 | 10:37 AM

bigbo62

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6th Gear

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Alright, I'll pick up a temp gun today and test it. How would I check the fan clutch?

Sep 23, 2025 | 11:36 AM

Junktownbill99

Fleet Mechanic

Joined: Nov 2022

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Quote:

Originally Posted by bigbo62

Alright, I'll pick up a temp gun today and test it. How would I check the fan clutch?

Spin it by hand, if there's no drag, it doesn't work. It should also howl when the engine gets hot.

Sep 23, 2025 | 04:32 PM

Mr.Lars

Mountain Pass

Joined: Aug 2025

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What condition is the fan shroud?
Does the alternator charge level drastically change at idle vs road speeds?

Sep 23, 2025 | 05:16 PM

bigbo62

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6th Gear

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I just use the temp gun and at about the O on the gauge it was 195, and at about the L it was at 230. I also spun the fan and there was resistance and it would stop spinning once I let go.

Sep 23, 2025 | 06:09 PM

bigbo62

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6th Gear

Joined: Jun 2024

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Never mind, forget everything I've said I've solved it. Some genius (me) set the timing at 20 so now I just set it to around 10, so I think I'm good now.