Fluctuating temperature guage.

[VirginiaMonkeys]

Today I drove about 5 miles and then turned off the vehicle. After about 10 minutes I started it up again and it idled for about 10 minutes. I noticed the temperature guage was at the top as far right as it could go, and the check engine light was on.

As soon as I put the truck in gear and revved the engine to go, the guage dropped to the normal position.

If I drive down the road, the guage hits the top if I'm decellerating or at a contant speed. If I accelerate, the temperature guage drops to normal.

If it's idling in the driveway it won't change in N or P by giving the engine gas, but if I put it in gear with one foot on the brake and give it a bit of gas, the needle will drop some.

I just got done replacing the thermostat with a OEM spec one from AutoZone, and a new radiator cap (pressurized).

None of that has helped with this one.

Any ideas? Any diagnosis I can perform to find the problem?

Thanks.

 

[Billy177]

check your fan clutch and make sure see if it is really overheating or just a gauge prob

 

[88vert]

Did you put the thermostat in the right way?

 

[MONMIX]

I am gona say air bubbles.

The hot air will give you all sorts of funkey readings to the hot side of things.

Burp the system and top it off.

Check also what those two said. You can't be too careful with engine heat. Bad things could happen with an over heat.

 

[BillWms01]

My daughter's 4.0L OHV Exp was acting like that a couple of weeks ago. Gauge would go to hot after the engine was initially started, and then come back down. Mine appeared to be pretty random. As far as I could tell, it wasn't really running hot, so I figured it was a sensor.

I replaced the coolant sensor (at NAPA, you have to ask for the temp "switch"; the "sensor" is the one beside it that inputs to the computer.) and the thermostat. Back to normal now.

Hope this helps...

 

[VirginiaMonkeys]

The repair guy replaced the guage in the dash yesterday. It's working fine now... BUT the radio doesn't work now and the brake light stays on.

$430 for something I could have done better for $50.