I have a 96 legacy outback with the 2.5 engine and its automatic and i was wondering why it keeps overheating it seems like everytime i drive for about 3 to 4 hours it overheats when i check the oil it is full when i check the radiator all the antifreeze goes right into the recovery tank when i let it sit to cool all the antifreeze disappears. I put a new oil filter on and put new oil in, i changed out the temperature control swich and the cooling fans work, i put a new radiator cap on and changed the antifreeze, then we burped it twice. no oil leaks or water leaks no where, no smoke no blown head gaskets everythings good on it beside the antifreeze disappearing and overheating. if any1 can help me thanx

Overheating and coolant transfer to recovery tank/coolant disappearing are signs of Head Gasket failure. Best way to confirm it is to do a Combustion Gas in coolant check either with a chemical kit or a combustion gas analyzer.

 

Clogged heater cores have been known to cause overheating (restricted coolant flow). Could also be water pump.

Edited April 26, 201015 yr by Mike104

Classic head gasket failure. It's so common with that engine that you can basically bank on the original gaskets failing at some point before 200k - very often before 100k.

 

What you describe is EXACTLY how they act. They always do it after driving for a while and blowing the coolant into the overflow bottle. That is a sign that the system has too much pressure - it's letting exhuast gasses into the cooling system and causing higher than 13 psi in the system - blowing the cap seal and pushing the coolant into the recovery tank. When it cools it creates a vacuum and pulls it back in.

 

GD

Edited April 26, 201015 yr by GeneralDisorder

I didn't see any mention of a new thermostat. Replace the t-stat with a genuine Subaru one from the dealer, refill and burp the system, topping off the overflow tank to correct level.

 

If it still overheats then suspect an internal headgasket leak.

 

Search this forum for plenty of info on HG leaks.

 

Did I mention it should be a GENUINE Subaru T-stat, aftermarkets do not work well in Subarus.

 

FYI: internal headgasket leaks do not produce "smoke" out the tailpipe. Hot compression gases are forced into the cooling system which creates air pockets in the water jacket that stop coolant flow and cause overheating.

Edited April 27, 201015 yr by Suzam
Add'l info

A bad thermostat would show itself long before 3 to 4 hours of driving and in any case his problem is due to over-pressure, not a lack of circulation.

 

GD

A bad thermostat would show itself long before 3 to 4 hours of driving and in any case his problem is due to over-pressure, not a lack of circulation.

 

GD

 

I agree, but a finicky thermostat might cause a similar problem. If wrongturninwv wants to do an exhaust gas test of the coolant to confirm a bad headgasket. I was suggesting an inexpensive T-stat replacement before resigning to a blown headgasket since he has had it happen every time he drives 3 to 4 hours.

 

If the radiator cap is loosened on a hot engine, the coolant will flow into the overflow tank from natural expansion.

 

wrongturninwv: is the temp gauge steady until the overheating and then pegs the meter or is there a fluctuation in the needle?

if it were me i'd just replace the head gaskets . i'm like 99% positive that is the problem . i had the same symptoms on my 97 obw and i fought with it for a month . new t'stat (oem) new rad cap (oem) all new hoses , flushed the radiator ; all to no avail . finally i broke down and did the head gaskets and corrected the problem . the cost of a new gasket kit , new head bolts and a few other odds and ends is well worth it . i did the job myself and only took two weekends . maybe 20 hours worth of work . or if you're not in to the diy thing it cost like $2500 at a shop . so if money is an issue ......... i dunno know what to tell you .