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Old 01-15-2012, 10:45 PM   #1
NASIOC Supporter
Member#: 558
Join Date: Nov 1999
Chapter/Region: NWIC
Location: Kent, Wa
2002 WRX sedan
midnight black pearl

Default Wrx overheating

Hey guys need some help. Also dont ask ive already searched by butt off.

My cars temp sensor goes towards red when i drive for more than 10-15 minutes. I never let it get past the last line on its way! The heat gets up to normal operating temp and then after about 5 minutes there it starts to rise quickly. If I throw the heat on high the temp levels back out to normal operating temp.

Somethings i have tested. The fans don't seem to cycle if i turn the car on and let it sit till it warms up. Note that the car does not overheat when its just sitting parked and running, it will continue to run at normal operating temperature but the fans will never kick on. The fans do work i checked the fuses and also with the key in just the on position and the dial on defrost the fans will come on. Also the top pipe is hot and the bottom pipe is very very mild while just sitting idling. The thermostat is a brand new oem unit. There are no leaks around the radiator it is the factory original but seems to still be in good shape. I'm not losing any coolant the level has not dropped.

The only other thing i can think of is the engine temp sensor. The car has been burped completely and checked for air bubbles more than once. There is absolutely no air in the system that i can get out anyway. The top pipe to the rad is firm when the car is running so the pressure is there. I have looked in the overflow bottle while its running there are no air bubbles (possible sign of HG).

One thing i need to double check is if the fans come on at all while driving. I think they do but they must come on at to high of a temp which ends up being to late to cool down what heat has built up.

This is very perplexing and any help would be great.

Mark T.
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Old 01-16-2012, 03:16 AM   #2
Scooby Specialist
Member#: 13815
Join Date: Jan 2002
Chapter/Region: SCIC
Location: Good ol Temecula
02 GCRally prepped
277TQ 281HP 19PSI


Well first, since the t stat is next to the bottom hose, it should be almost the same temp as the top when it fully opens. If it gets warm like you said, it may be sticking upon opening. Which I've had to go through 3 different t stats on one car, before getting one that opens correctly.
I would start there because, if you can make the fans come on manually, there has to be a reason why. And i think because you are getting a partially stuck t stat, that might be why the fans aren't coming on at idle.
And if you just installed the new t stat and nothing else, that would lead me to believe that is the problem.
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Old 01-18-2012, 05:54 PM   #3
Scooby Specialist
Member#: 26770
Join Date: Oct 2002
Chapter/Region: South East
Location: Tampa
'02 WRX
midnight black


Also, turning on the defrost simply triggers the a/c which should be one fan, but not both. Figure out which fan is for the cooling system, and start with the plug (each fan has it's own on either side). FYI these are 2 speed fans, and if you have installed aftermarket fans you may need to rewire (research before cutting/ splicing anything!).
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Old 01-18-2012, 11:41 PM   #4
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Member#: 293956
Join Date: Sep 2011
Chapter/Region: South East
Location: Holly Springs, NC
2005 WRX w/ VF39


My Subie was overheating for a little bit. Turned the heat on and it would go back to normal-ish temp. Checked the fluid level and it was a little low and the radiator cap's seal on the expansion tank was completely shredded.

Replaced the cap and topped off coolant and now it's been fine ever since.

Hope you get it fixed.
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Old 06-06-2014, 02:32 AM   #5
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Member#: 390539
Join Date: May 2014

Any update on this?
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