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Temperature gauge says hot but it is not overheating

Tiny
TJALDRICH22
  • MEMBER
  • 2002 SUBARU WAGON
  • 4 CYL
  • AUTOMATIC
  • 202,000 MILES
I have a 2002 Subaru outback Impreza sport wagon. Just recently the gauge started showing it was hot. But when I would pull over and check, nothing was overheating.
Then it became erratic and was going up and down. Finally, just stayed on H.
We replaced the sensor, top radiator hose, thermostat, and flushed coolant. Still on H but nothing is overheating. I was told it might be (God forbid) the head gasket. So, I put some sealant in for that. Nothing. Help?
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Saturday, May 28th, 2022 AT 7:14 PM

6 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

When you first turn the key on to the run position (engine cold) does the gauge immediately indicate the engine is hot? If so, then suspect there is a short in the wiring to the sensor.

However, there are two coolant temperature sensors on this vehicle. One is for the cooling fans and the other is for the computer/gauge. Take a look at the pic below and let me know if that is the one you replaced.

Also, take a look through this link and let me know if you have any of the symptoms:

https://www.2carpros.com/articles/head-gasket-blown-test

Let me know.

Joe

See pics below.
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Saturday, May 28th, 2022 AT 11:21 PM
Tiny
TJALDRICH22
  • MEMBER
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Hi,

Thank you so much for responding.

I believe it was the engine coolant temperature sensor.

And it doesn't go immediately to hot but within a couple min. Even if the car itself is still cold. As I said, nothing indicates the car is actually overheating.
Also, I did use Blue Devil the day before yesterday and it doesn't seem to be helping.
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Sunday, May 29th, 2022 AT 11:55 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

Okay. Here is an interesting thought: The sensors (two of them) are both called coolant temperature sensors. If I recall, the one for the fans is on the radiator. The other is on the engine. Do you recall where the one was you replaced?

Also, this still could be a head gasket-related problem. Did you look through the link I attached above?

Let me know.

Joe
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Sunday, May 29th, 2022 AT 8:21 PM
Tiny
TJALDRICH22
  • MEMBER
  • 4 POSTS
I'm pretty sure it was on.
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Monday, May 30th, 2022 AT 7:34 AM
Tiny
TJALDRICH22
  • MEMBER
  • 4 POSTS
Oops, it was on the engine.
I didn't do it myself. My mechanic did it all.
So, the link was a little helpful.
The mechanic doesn't believe there's two sensors. And the car doesn't have any other gasket symptoms that were mentioned.
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Monday, May 30th, 2022 AT 7:40 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

Okay, if there are no mechanical issues (sensor, head gasket, timing, restricted exhaust) then it has to be electrical. The sensor functions with electricity from the engine control module. Has all wiring been inspected including the connectors?

Let me know.

Joe

See pic below. This is from my manual.
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Monday, May 30th, 2022 AT 6:57 PM

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