Temperature gauge says overheating

Tiny
TABITHA35
  • MEMBER
  • 2003 MITSUBISHI ECLIPSE
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 115 MILES
My temperature gauge randomly says it is over heating. Maybe once a day. Heater starts to blow cold. Changed thermostat twice, change radiator cap. I can leave it idle fine, drive fine, then out of the blue my temperature goes way up close to red. Turn heater off then back on and temperature goes down slowly. In the morning letting it warm up fine no problem. It is crazy to me. No water on floor.
Friday, December 1st, 2017 AT 7:16 PM

5 Replies

Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
Turning the heater on/off makes a difference could mean air trapped in system, are you having any coolant losses issues?
When gauge is indicating overheating, are the cooling fans working then?
Did you try a diagnostic scan to check for trouble codes? If the coolant temperature sensor is faulty, it could leave a record in the engine control module.

If the ground circuit for the coolant temperature sensor or gauge is poor, it can result in the phenomena too.
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Friday, December 1st, 2017 AT 7:50 PM
Tiny
TABITHA35
  • MEMBER
  • 3 POSTS
No check engine light, no coolant loss that I can find. Should I just change the temperature sensor?
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Friday, December 1st, 2017 AT 7:53 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
If I may jump in here, to me it sounds like you have a blown head gasket which will fill the cooling system with exhaust which makes the engine overheat and the heater to stop working. These cars are famous for blown head gaskets.

Please run this test to confirm the failure.

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

Please let us know what you find. We are interested to see what it is.

Cheers, Ken
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Monday, December 4th, 2017 AT 1:33 PM
Tiny
TABITHA35
  • MEMBER
  • 3 POSTS
No leaks and no coolant in oil, had it changed and checked.
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Monday, December 4th, 2017 AT 3:01 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
A head gasket can still be blown without putting coolant into the oil. Did you do the chemical test?
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Tuesday, December 5th, 2017 AT 1:29 PM

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