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Old 07-12-2013, 09:43 AM   #1
Nudnik
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Member#: 284947
Join Date: Jun 2011
Chapter/Region: TXIC
Location: Denton, TX
Vehicle:
2002 WRX Wagon
WRB

Default Bizarre overheating randomly

Here's the deal, I rebuilt my engine 6 weeks ago (skipped timing & bent a couple of valves). I put everything back together & have been driving it 100+ miles everyday to & from work ever since with no issues (except for what I'm about to describe).

About a week ago I was idling in my driveway & noticed my temp gauge started climbing. I turned the car off for 4 or 5 minutes, then fired it up & drove round trip thru town (15 miles with a couple of stop lights) & had no overheating at all (according to the gauge).

For the past week I've been driving it to & from work (some stop & go traffic) with no overheating issues (according to the gauge). Yesterday, I was driving thru town (after my 50 mile [mostly highway] drive home from work) & noticed the gauge started to climb. I turned the heater on & saw the gauge drop back down. I turned the heater off & the gauge stayed normal while I was moving. I stopped at a stop light & the gauge climbed so I turned the heater on. The gauge dropped back down so I turned the heater off while I was still at the stop light & the gauge stayed at a normal level for 1 to 2 minutes while I was still at the stop light. I drove away from the stop light & the gauge started to climb. I turned the heater back on & it dropped back down to normal. I stopped at another stop light (2 or 3 minutes) & the gauge stayed at a normal level. I drove 1/2 a mile home with the gauge at a normal level.

The reason I'm confused is b/c it seems to overheat randomly. It overheated while I was driving & while I was stopped. It did NOT overheat while I was driving & while I was stopped. Turning the heater on did seem to cool it down but once it cooled down I could turn the heater off & the temp would stay in the normal range. I haven't checked to see if my fans are coming on yet (I'm hoping it's just a blown fuse or something simple).

Do water pumps randomly work (pump is 5K miles old) or stop working?

Could my T-stat be randomly working?
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Old 07-12-2013, 10:02 AM   #2
Dr. octagon
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Join Date: Feb 2008
Chapter/Region: MAIC
Location: Fredericksburg
Vehicle:
02 Kinugawa
psm

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possibly t stat, or more than likely small leak in either rad hose (probably lower hose by t-stat, or areas around t stat).

Try burping the system again, i could be you still have air in the system.
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Old 07-12-2013, 11:42 AM   #3
Nudnik
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2002 WRX Wagon
WRB

Default

Quote:
Originally Posted by Dr. octagon View Post
possibly t stat, or more than likely small leak in either rad hose (probably lower hose by t-stat, or areas around t stat).

Try burping the system again, i could be you still have air in the system.
You think it could be air even though I've been driving it 6 weeks? Surely the overheating issue would have reared it's head before now. I'll check for a leak when I get home from work & let you know.
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Old 07-12-2013, 11:49 AM   #4
Dr. octagon
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It could be, i beat my heat against a wall trying to figure out why i had no heat at idle, only when moving.

Hole in lower rad piping, actually the hose that leads from the t-stat to the smaller hard coolant pipes in front of the oil pan.

Not fun, and very hot in that location.
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Old 07-12-2013, 01:15 PM   #5
recce02
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Location: Good ol Temecula
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277TQ 281HP 19PSI

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Get a coolant pressure tester, if you dont have one you can rent one from places like autozone. 16 psi is what you test the system at. Also with that tester test the radiator cap/s.
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Old 07-12-2013, 03:17 PM   #6
alexandern05
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Location: delaware county pa
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04 wrx v7 sti swap
agile tuned 389hp 342ftlb

Default

Probably air in the system fill from the upper resavaior not the radiator or possibly thermostat
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