So back in December of last year, I bought a nice 98 Subaru Forester with the 2.5;

Recently, I've had developed a weird cooling issue; considering I have the 2.5, I know for the fact the previous owner had the head gasket replaced at a reputable Subaru dealer here about 2 years ago, I know its not that infamous issue.

Whats going is that the car warms up to proper temperature but anywhere between 30 to 1 hour later, the temperature gauge will go up but not into the red zone; coolant is being dumped back into the overflow causing it to pour out, but goes back into the radiator when the engine is off and cooling down. There is no water/oil contamination at all. Engine performance is normal even when it gets hotter than normal. And if I am moving on the highway at 55+, I will never have any issue with the temperature going higher; but if I get off the highway or moving it will creep up but sometimes even correct itself. Then again, I also once was in a parking lot and it stayed at the right temperature for 45 minutes idling. Heater heat level if I turn it on during its hot is perfectly hot.

It reminds me kind of a water pump issue but not quite...I'm not sure here...

start with the thermostat.

Also fan? Temp sensor? Subaru?

Hey, I have the exact same problem with mine, found the fans were not coming on due to one of the wires for the fan connector having come out.

I've checked the fans; they are both working.

Reading up thermostats and the Subaru; it seems like there's some aftermarket designs of them that are not compatable with the Subaru 2.5 cooling system...mainly ones with copper....hmmm...I'll need to reasearch who makes for Subaru their OEM thermostat...

Sound like a bad Temp Sensor to me.

I've seen the impeller slip on the shaft of the water pump on these.

So, I decided to play around with the Forester on the way home to see if I can find the method to this madness. I had a make few stops so I checked the coolant resovoir every time; the first stop the tank had very very very white foam at the top. Second stop the foam was gone and instead the coolant was right at the top and there was bubbles. Third stop was the same.

Again, the temperature gauge goes to 3/4 of the way up but does not go in the red when at speeds below 25 MPH. I even picked a busy drive thru tonight and while it did climb up to the 3/4 while idling, the minute I got back on the road at speed, the temperature returned to normal. And then on the highway even on hill climbs no problems at 55 plus.

I would throw one of those exhaust gas checkers on there to see if you got combustion gasses in the cooling system. These things can have really strange symptoms with head gasket problems. Mine hasn't been acting up as much tho I haven't been driving it but I'm intending to pull the engine and do timing belt and re gasket it this winter.

Posted by sleeperspirit I would throw one of those exhaust gas checkers on there to see if you got combustion gasses in the cooling system.

i was thinking the same thing when I heard "bubbles".

Confirmed its a head gasket leak...internal one so its blowing exhaust out but its in the early stages.

Calling around today thru my contacts in the rally world, I found a Subaru shop here that they could do a 2.2 swap for LESS than a head gasket job on my 2.5 DOHC at 1200 bucks which would be much better. I'm going to do that instead once they confirm they have a 2.2 in stock.

That's the way to do it, I just junked a great running 96 legacy 2.2 I was going to use to swap in mine. The 2.2 is just a tad slower but way more reliable and simple plus parts are cheaper and it's not a valve smasher.

Just got the swap done...its awesome again...

So this past week, I noticed again the temp gauge was creeping up a tad at idle but would settle down. Then one day there was a small puddle of coolant under the Forester at work; took a look and thankfully, it was just the water pump bypass hose with a few pinhole leaks. Replaced it for only 4 dollars.