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Old 07-01-2010, 03:56 PM   #1
azguard4
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Default Overheating - Need Quick Help!

I have a 1993 Subaru Legacy. I'll be taking it through the mountains in AZ. Whenever I do this, especially in the summer it tries to overheat with the A/C on, I have to turn off the A/C through certain passes.

I never have any problems down in Phoenix with it, even when it's 115 degrees! Is there something actually wrong or is it just the way it's going to be. I have 2 kids so turning off the A/C just isn't an option.

I'm thinking about replacing the thermostat. Not sure what else to do? It has a brand new radiator and the coolant is a beautiful bright green.
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Old 07-01-2010, 05:51 PM   #2
flightwatch
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It's most likely caused by overloading the motor. The motor is already having to haul the weight of the car + you, your kids, and your stuff up a rather steep grade at an altitude that the car is not accustomed to...not to mention the oat.

You can try a colder thermostat, but I would try hood spacers so that the motor could dissipate heat better
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Old 07-01-2010, 06:13 PM   #3
azguard4
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Great thanks. That seems to be the answer I've been getting; It's not really that anything is wrong, it's just how it's going to be.
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Old 07-02-2010, 02:20 AM   #4
AWDenvy
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Thermostats are like ~$20, and take 15 minutes to replace.

But, like flighwatch said, it sounds like your simply overloading the motor. There's only so much it can take before its cooling system becomes insufficient. Hood spacers and a colder t-stat are your best options.
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Old 07-02-2010, 08:44 AM   #5
Patrick Olsen
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Quote:
Originally Posted by flightwatch View Post
You can try a colder thermostat, but I would try hood spacers so that the motor could dissipate heat better
Could you explain how either of those will help? I don't understand.

I think you should try a new radiator cap, possibly a higher pressure one (16psi vs the stock 13psi).

Pat Olsen
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Old 07-02-2010, 11:26 AM   #6
flightwatch
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Quote:
Originally Posted by Patrick Olsen View Post
Could you explain how either of those will help? I don't understand.

I think you should try a new radiator cap, possibly a higher pressure one (16psi vs the stock 13psi).

Pat Olsen
I would be more than happy to...

A colder thermostat would open at a cooler water temperature this giving the cooling system a head start on the issue. That really wouldn't help at all though once the motor was at operating temperatures, and would only delay the problem he is having from occuring.

Hood spacers would allow more air into the engine bay. They would also allow more air to escape the engine bay. The outside air (which is much colder than the engine) would aide in helping the engine stay a little bit cooler...albeit not much, but any little bit helps. They would also allow the heating created by the motor to escape better

My suggestions are more like cheap band aids than they are permanent solutions. I question how a radiator cap would fix the issue...
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Old 07-05-2010, 11:53 PM   #7
Patrick Olsen
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Quote:
Originally Posted by flightwatch View Post
A colder thermostat would open at a cooler water temperature this giving the cooling system a head start on the issue. That really wouldn't help at all though once the motor was at operating temperatures, and would only delay the problem he is having from occuring.
Exactly why I was wondering why this was suggested as a possible fix.

Quote:
Originally Posted by flightwatch View Post
Hood spacers would allow more air into the engine bay. They would also allow more air to escape the engine bay. The outside air (which is much colder than the engine) would aide in helping the engine stay a little bit cooler...albeit not much, but any little bit helps. They would also allow the heating created by the motor to escape better
When the vehicle is stopped or at slow speeds, yes, the hood spacers will vent heat. Once you get up to speed, though, the base of the windshield is a high pressure area. Having the hood raised up simply allows air in at the back of the hood (think muscle car cowl induction), which isn't going to help cooling in the slightest because system pressure was allowed to escape through the dirty/damaged seal.

Quote:
Originally Posted by flightwatch View Post
I question how a radiator cap would fix the issue...
A properly functioning radiator cap keeps the system pressurized, which raises the boiling point of the water/coolant. Try replacing your stock radiator cap with one that's only rated to 0.5bar or something like that - your cooling system probably won't be very happy about that. Subaru actually had a TSB out there for Outbacks that dealt with leaking radiator caps (due to mung building up on the seal) that would result in overheating.

Obviously, I can't guarantee the radiator cap will help. It may be that his coolant system is just overtaxed by the AC and the high load on the engine. But for under $10 and maybe 30sec of work, it can't hurt to replace it, particularly if it hasn't been replaced in a long time.

Pat
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Old 07-06-2010, 06:03 PM   #8
ocddad
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First, if you haven't in a while, flush the cooling system and bleed it properly. Check belts/pulleys too...sounds like heavy hauling ahead.

As far as the ac...might be worth it to get it checked properly from trusted mechanic. If it's low on 134a, you'll be running it much more than it needs to run...as in continuous cycling of compressor...I'm thinking if it's topped off, you might get a little luckier.

But, based on your prior experiences, I'd make sure you've just kept up with proper maintenance, fluid changes, etc...

Oh, and not so sure about a higher pressure rad cap...just seems you raise the pressure there, more pressure will build up and maybe find another place to leave. If it's not blowing at 13, don't go up to 16...and make sure system isn't overfilled...on my car (not a subbie) overfilling expansion tank guarantees a forthcoming rupture.

HTH

Doug
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