Overheating help

bfg9k · Feb 20, 2005

My Subaru ('98, 2.2L, auto, 107k miles), fresh off of its transmission rebuild, is now plagued by overheating. It started after a bad thermostat was replaced. Some investigation revealed a broken air plug, so I replaced that, and the mechanic then replaced the thermostat again, just to be sure.

The car overheats oddly...it'll be fine for about 20 minutes of driving, and then the temp gauge will slowly start rising and will get about 3/4 of the way up. I can cool it down by cranking the cabin heat. This happens during both highway AND slow speed driving, making it a little weird. I am suspecting either a bad coolant temperature sensor, a bad radiator, or both. Maybe there's still air in the system, but I've burped it several times and now more seems to come out.

Any thoughts, anyone?

Quest · Feb 20, 2005

mechanic incompetency... go find a Subaru specialist to deal with it. I bet he can figure it out in 15 mins.

Not the Autorx Frank · Feb 21, 2005

sounds like a headgasket

send the oil in for a used oil analysis, test for coolant, if tis neg then must be flow on the rad.

bfg9k · Feb 21, 2005

If it's a slight headgasket leak, does anyone have any thoughts on Bar's Leaks or something similar? It's going to a Subaru dealer on Thurs for a diagnosis. Thanks!

55Test · Feb 21, 2005

quote:

Originally posted by bfg9k:
but I've burped it several times and now more seems to come out.

Any thoughts, anyone?

Based on that one bit above, I'd say it might be a headgasket.

Drew99GT · Feb 22, 2005

quote:

Originally posted by bfg9k:
If it's a slight headgasket leak, does anyone have any thoughts on Bar's Leaks or something similar? It's going to a Subaru dealer on Thurs for a diagnosis. Thanks!

That stuff MAY give you headaches later down the road. You may be sacrificing a plugged up radiator/heater core in the future for a somewhat sealed headgasket. It'll be better to get it profesionally fixed.

Mike_dup1 · Feb 22, 2005

It could be the radiator. Many think a raditor shoudl last forever but they corrode on the inside reducing their effectiveness. Also the raditor may not be holding the correct pressure, need to get that checked.

Gary Allan · Feb 22, 2005

Are you sure your fan is working properly?? This 20 minute time limit kinda has me thinking. You have a rejection capacity problem which is cured by the addition of the heat rejected through the heater core.

Sure it could be a plugged rad ..but I would think that your heater core would be just as corroded ..but it works well in rejecting heat.

I would think a head gasket wouldn't limit itself to the 20 minute time limit.

This event kinda appears linked to oil temp (which we're learning is about a 20 minute event).

Not the Autorx Frank · Feb 22, 2005

(sneaks in behind gary)

fan clutch?

(sneaks out undetected)

ZR2RANDO · Feb 22, 2005

Any chance when the t-stat was replaced too much gasket sealant was used and it squashed out into the coolant flow and perhaps clogged a couple of radiator tubes??
I had a intake bolt break years ago and the repair shop used WWAAYY too much gasket sealer..I found that sealer in the radiator several years later when the radiator could no longer handle extra hot days..A radiator with low heat rejection capacity (as stated above) could easily account for the original symptom description. If that radiator is partially obstructed/clogged it may not transfer enough heat to even activate the fan clutch..

mechtech · Feb 22, 2005

bfg - If the problem started AFTER you replaced the thermostat, why did you replace it in the first place? For no reason? What were the previous symptoms?

kenw · Feb 23, 2005

t-stat in backwards? it happens, you know...

solved a very similar problem for friend last year. yup, t-stat was in backwards....ran fine, would climb like crazy then all of a sudden drop to near normal. Once it opened, it was fine for as long as the car was running, but due to the sensing element being on the wrong (cool) side, it was delayed in opening. Scared the bejeebers out of him. Took 5 minutes to fix and it's been fine for almost a year.

the temp-sensing side should face the engine, fwiw.

also, my son's accord had a similar problem but it was some gunk had attached itself to the t-stat and wouldn't let it open all the way. Kinda like the previous post that mentioned the gasket. Some mechanics ascribe to the "more is better" rule when using liquid gasket stuff....altho my son's accord uses a rubber gasket so we don't know where the gunk came from.

[ February 23, 2005, 05:19 PM: Message edited by: kenw ]

Overheating help

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