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Old 03-03-2013, 09:16 PM   #1
stockk5
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Join Date: Mar 2009
Default 06 Impreza 2.5 overheating

Hey guys, I am pretty sure I bought a lemon.. so now I need to fix it. The car was traded into a dealer with a blown head gasket, the gasket was replaced, heads machined, new timing belt/thermastat and waterpump done. So I bought it, been driving it for 9,0000miles been working great up until a few weeks ago. This only happens after 1 or more hours on the highway at cruising speed in 5th gear. 75mph or so.

I checked the antifreeze, and it was leaking a little bit out of the lower radiator hose, and realized hmm he didnt change the lower radiator hose, so I put a new one on thinking the old one may have been streched out a bit and not clamped properly.

The car lately has been getting hot after those kinds of trips and up in the RED zone, and so I would pull over, check the fluids, everythings ok... and then merge back onto the highway. While merging and the temp guage still reading hot, I would be accelerating quickly with high RPM's and then the temperature would INSTANTLY drop to normal temp level and be good for the rest of the trip. I have found this to be an effective solution, if hot, drop a gear (higher rpms) and the temp goes down. (soo maybe waterpump??)

This has been an on going issue. I have not had a chance to do anything more than the hose. My next step I want to replace is the tstat, i would like to avoid the waterpump job but obviously willl if I have to. I have read a few of the threads on overheating so far but nothing similar to my situation.

What is your thoughts?
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Old 03-03-2013, 09:22 PM   #2
scarney1988
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Sounds like a sticking Tstat. Vibration of engine change allowing it to jar free. Maybe there is some build up on it or something. Replace it and burp your coolant properly.

Could always test by running no T-stat for an extended highway drive and make sure you experience no futher overheating.
.
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Old 03-03-2013, 09:57 PM   #3
stockk5
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Quote:
Originally Posted by scarney1988 View Post
Sounds like a sticking Tstat. Vibration of engine change allowing it to jar free. Maybe there is some build up on it or something. Replace it and burp your coolant properly.

Could always test by running no T-stat for an extended highway drive and make sure you experience no futher overheating.
.

Yeah I am hoping this is the step that will fix it. Mind giving me some tips on burping the coolant properly?
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Old 03-03-2013, 10:45 PM   #4
scarney1988
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I would recommend getting this funnel

Then:

1. attach base of funnel by selecting proper adapter and cap
2. attach funnel and fill system with coolant (after making sure the system has been resealed) and fill with coolant until the system will accept no more coolant
3. fill the funnel halfway coolant and start the vehicle, you must never let the funnel become empty.
4. turn heat on high in the interior cabin and and allow the vehicle to idle until the coolant fans come on, while making sure that coolant stays in the funnel (monitor coolant temp in the cabin periodically and make sure not overheat
5. make sure heat is hot coming from the vents and turn vehicle off
6. install rad cap and test drive

I would recommend chocking the rear wheels, setting the e brake, and jacking the front end of the car up to lift the radiator cap aboe to the highest point of the coolant system.

Ill ad more later when im not running low in sleep.
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Old 03-04-2013, 12:51 AM   #5
Preludicrous
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Location: Tucson AZ
Vehicle:
2006 2.5i Wagon
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Quote:
Originally Posted by stockk5 View Post
Yeah I am hoping this is the step that will fix it. Mind giving me some tips on burping the coolant properly?
Most systems have a bleeder valve similar to the ones on your brakes. On my Accord it is on the tstat housing. I'm sure there are in-depth instructions online, but basically you just fill the coolant up to proper level and then run the engine with the valve open and heater running full blast until the fan kicks on. Or you can always just leave the rad cap off and do the same thing. Burping (or bleeding) the coolant system helps prevent vapor lock (air bubble trapped in system) which will cause overheating. The quickest way to a vapor lock situation is removing or replacing a rad hose and not burping afterwards.
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Old 03-04-2013, 10:18 AM   #6
scarney1988
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Im in the philadelphia area if you are local I can use a vacuum bleeder to refill your system at my shop.... prolly not an option but figured ide offer.
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Old 03-04-2013, 03:09 PM   #7
Smitithus
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How's your overflow reservoir look? is if filling up? I agree with scarney, swap tstat then burp with funnel and front end up. Next guess for me is air pockets forming in engine (ie HG's again). really it's the only other thing that can cause such a rapid change in temp. Water pump is unlikely, usually they either work, don't work or leak, but it's worth a shot.
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