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Stephon

Heater and Temperature Problem

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Over at the NASIOC forum, 1 Lucky Texan suggested that someone here may be able to help me with a problem. Here's what I posted at NASIOC:

 

 

I'm driving a '97 Legacy Outback automatic with 100K+ miles on it.

 

The weather is cold here, so after the car had warmed up I turned the heater on, but got cold air coming from my vents.

 

About 2 minutes after dicovering that, my temperature gauge shot all the way to the top.

 

I turned for home, turning the car off as needed to let the engine cool.

 

Seemed normal otherwise. No odors or smoke coming out of the car.

 

Any thought on what's going on?

 

[snip reply]

 

could a bad thermostat cause both these problems?

Any help or suggestions are greatly appreciated. Thanks.

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A lot of things could cause this.

 

Did you have the coolant changed lately? Or any servicing that would have caused the coolant to be draining and refilled?

 

Yes, it can be t-stat, hoses, water pump, etc. But... (big but)...

 

I hate to be the first to say it, but your year, age and mileage make you a prime candidate for head gasket failure. I'd check the coolant expansion bottle asap to see if you have any gooey oily looking sludge in there and/or bubbles coming up through it.

 

I have a 97 OB myself... been there... bought the t-shirt.

 

Commuter

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MY '98 Outback has had the same symptoms as yours on two different occasions, a couple of years apart.

 

The first time I assumed Thermostat and changed it. On road test, same overheat. I thought I put it in upside down or something. All of a sudden while going up a fairly steep hill, the temp went back down and was fine, up until this weekend. I think it's been 2 years, maybe just one.

 

This time it actually over heated. This car was in a deer collision a couple weeks ago and the radiator was replaced so it's got new fluids, could be something got stuck.

 

Again though the hill trick worked.

 

I know there's a trick in filling the radiator in these. Instead of going through the radiator cap, which would be the obvious method, you have to take a plastic plug out of the other end of the radiator.

 

I've come to the conclusion that its some kind of vapor lock or loss of flow. I had the shop plug into the computer and no codes were recorded.

 

Try the hill trick, front end up. Also fill from the opposite end of radiator.

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MY '98 Outback has had the same symptoms as yours on two different occasions, a couple of years apart.

 

The first time I assumed Thermostat and changed it. On road test, same overheat. I thought I put it in upside down or something. All of a sudden while going up a fairly steep hill, the temp went back down and was fine, up until this weekend. I think it's been 2 years, maybe just one.

 

This time it actually over heated. This car was in a deer collision a couple weeks ago and the radiator was replaced so it's got new fluids, could be something got stuck.

 

Again though the hill trick worked.

 

I know there's a trick in filling the radiator in these. Instead of going through the radiator cap, which would be the obvious method, you have to take a plastic plug out of the other end of the radiator.

 

I've come to the conclusion that its some kind of vapor lock or loss of flow. I had the shop plug into the computer and no codes were recorded.

 

Try the hill trick, front end up. Also fill from the opposite end of radiator.

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Well!

 

On 17 November, with no history of cooling issues, after a 30-minute commute, my 1999 OB Legacy Wagon (man tran) pulled up steaming and smelling of hot coolant. The temp gauge was normal. I figured I had a pinhole leak, and waited for it all to cool off before I tried to look at it. When I got down and looked, no puddle; no obvious drips; little bit of coolant on the engine. The kicker--no coolant was visible in overflow reservoir or in radiator.

 

Topped up coolant and drove home—no problems, temp stayed normal.

 

Took car to Soob specialists—they pressure tested, no problem. They test drove car for 30 miles, and had the same result—loss of coolant. Replaced thermostat, same problem. Replaced water pump, same problem. Pulled engine—head gasket fine, block not cracked.

 

HOWEVER, the cylinders were scored, and the exhaust valves were irreparable.

 

Has anyone had anything similar?

 

V

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We may never know for sure, but I'd guess you had air in the system. I think, if the overflow bottle is ever empty, subes can suck an air bubble in to the radiator, and maybe because of the flow direction, it can be sent through the upper hose into the engine.(IIRC subes flow out the top hose to the engine?) Once there, maybe it insulkates an area longe enough to become superheated causing further expulsion through the cap/o'flow.

 

Since you waithe for it to cool before looking, we don't know if the o'flow tank had any coolant in it. If it did have some, it would've been sucked in after the cooling - um - probably.

 

btw- a meat thermometer and a pan of hot water will tell you if a thermostat is working. Just turn up the stove and see if it opens at/near the correct temp.

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