Mysterious overheating revisited ARRGH!

[salewit]

92 Legacy

 

About 2 years ago we were driving on the freeway and the thing overheated so bad that the engine stalled. Filled with water and went on our way. Nothing again for about a month of on and off freeway driving. Then it appeared again. We changed the radiator, thermostat (4 times!), all hoses and it did it again.

 

About a year ago I changed the head gasket. Had the valves in the head redone and and the heads ground. The car ran great for a year. Guess what? It's back!

 

I'm absolutely stumped. I took it to a Subaru dealer and ordered a check of hydrocarbons in the coolant. They said the test ranged up and down from 0-400ppm. Suggested a new engine at $4500 (surprise, surprise). I've now got it into another place to do the test again. So far they've driven it around town, on the freeway and it's been fine (of course it has... this is why I told them it was an intermittent problem). They say there is nothing wrong with the car. I just told them to run the hydrocarbons test and give me the numbers.

 

Anybody have any words of wisdom on this? The only thing that made me nervous about the head gasket replacement job I did was the unbelievably funky torque down process (tighten to X, loosen 1/2 turn, tighten to Y, loosen... etc, etc). I wasn't comfortable with it at all, but followed it to the letter.

 

Thanks!

Sam

[tunered]

how about a sticky therostat or a hose sucking closed,will it cool down if you pull over and let it idle?

[nipper]

Funky head gasket tightening is not a big thing. You know, the car is a 92, and it was severley over heated (causing it to stall thats pretty bad).

You know engines do get tired and worn out. They dont run forever, though they come close. Did somone check the cylinder decks as well as the cylinder heads for flatness.

Im going to assume this engine has some mileage on it. I would be more concerned with the fact the engine got baked. I would also do a leakdown test in the cooling system. Hydrocarbns looks for things escaping into the coolant, the leak down (or pressure test) looks for weakness into the cylinders etc etc.

Blowing another head gasket within a year is usually a sign of a note so perfect repair.

Also a compression test is in order. It is also possible that it is not a head gasket, but a cracked head or cylinder wall.

Cast iron engines can be overheated like crazy and stay structurally sound. Aluminum engines really dont like it and the heavy damage can show up at a later date, thats why its important to never let a modern engine get that hot.

 

nipper