Overheating Problem

[subaruman]

Hi everyone. I am new to this forum and I’m glad to have found it. I hope someone can help with my overheating problem. I have a 1991 Legacy wagon 202,000 miles. Out of the blue my car started to over heat I mean really over heat with the temp gauge pegged at the top. Pulling over to the side of the road I would let it cool and I would start it up again make it about 1 mile and it would heat up again. Doing this for about 10 miles so I could find a phone it stopped. The car ran cool and I was able to drive it 50 miles back home without any problem. Next day same problem. I pulled the thermostat and replaced it.. That did not help so I pulled the radiator and flushed it.. still nothing. I got pretty fed up with it so I pulled the thermostat out again and left it out. The cars temp is just fine with no thermostat, even runs a little cool. I’m at a loss and I would appreciate any help on this subject.. Thanks!!! PS the cooling fans work fine.

Jeremy

91 Legacy AWD 202k
91 Loyale 4x4 160k
84 Hatchback 4x4 130k

[Legacy777]

Symptoms you describe would have me looking at the possibility of a blown head gasket.

I'd check some other stuff too, but I wouldn't rule it out.

First check to see if you see bubbles in the coolant overflow tank while the engine is running.

Also, have you burped the radiator properly? There is a bleed screw on the passenger side of the radiator
http://www.main.experiencetherave.com:8 ... diator.jpg That needs to be open while filling and while letting the air get out of the system.

Also, if you used any thermostat other then a subaru thermostat that you get from the dealer, you are going to have issues. Most aftermarket thermostats are not the same physical dimensions as the subaru one. They also do not have the same lift or valve travel, or resitance to temperature change.

I speak from first hand experience that any thermostat but a subaru one will give you grief.

Also, I'd suggest doing either or both a cooling system pressure test, and a sniffer test of the exhaust to check for coolant.

[subaruman]

I had no idea about the thermostat issue. I'll try the Subaru one, does anyone have a part number?

I found no air bubbles in the overflow. I also bleed the cooling system right by unscrewing that screw.

Blown head gasket huh? It's possible I guess. I have no coolant in the oil and it never blows white smoke. How would I go about the coolant pressure test?

Thanks
Jeremy

[boostjunkie]

Bubbles in the coolant overflow never showed up when I blew my headgasket. You might wanna try hooking up a vaccum gauge up to your manifold. If the pressure reads more than -.60kPa at idle when your engine's warmed up, you most likely have a HG problem. Mind you, that more than -.60 is -.59, -.58, -.57, etc.

[Legacy777]

Check out the sticky part # thread in the 'stuff you need to know' forum it's in there, several times. as well as the gasket.

To pressure test the coolant system, you need a tester hand pump that screws onto the radiator cap opening. You pump & pressurize the system. If it holds pressure, then it's possibly not a headgasket issue. If you see it leaking down....it could be a headgasket issue, or could be radiator cap not holding pressure.

Do what boostjunkie said, check your vacuum level too.

t-stat is the easiest & cheapest thing to probably do.

[subaruman]

Thanks guys. I'll check the pressure of the cooling system and intake. I'll let you know what I find out!

Jeremy