Help with a 1998 Subaru Outback?

[Jesda]

I picked up a Subaru from the auction. It's a 1998 naturally aspirated 2.5L Outback wagon with 155,500 miles. It seemed fine when I drove it down the test track at the auction but on the drive home I encountered heavy traffic. That's when I slowed down and the temp needle shot up, almost to the "H" on the gauge. I fired up the heater and put it in neutral as often as I could and limped back to the dealership.

Since these cars have a reputation for head gasket failures, I bought a block test kit from Autozone along with some blue testing fluid. I tested it on the radiator filler neck as well as the overflow tank and no matter what I did -- putting it in park and revving, putting it on drive with a foot on the brake and revving -- I was unable to get the fluid to turn yellow which would have indicated the presence of exhaust gases in the cooling system.

It only overheats after getting off the highway. Once I get off the highway, the temp drops quickly if I hammer the throttle, shift down, and rev the engine. Idling in drive causes it to creep up.

The fans work and cycle on and off as they should.

I took it to my Saab mechanic and he checked for significant leaks, checked the fans, and concluded that the hardware seemed to be in order. He then burped the cooling system and removed "a lot" of bubbles. I picked up the car and got on and off the highway a few times but it didn't run hot until I finally made it out to the valley near my place.

I put the heater on full blast and limped home.

Annoyed with the idea of a broken machine (this is what keeps me up at night; I've been outside in 20 degree weather for an hour and half working on it), I drove the Subaru back to the lot and tried the block test again, this time on the radiator fill neck with a wide plastic 'straw' funnel to capture the exhaust gases without contaminating the solution with coolant. It stayed bright blue no matter what.

I tested the fluid on the exhaust tip to get a baseline and make sure that it was actually capable of detecting hydrocarbons and it was (quickly turned pale yellow), so my testing tools are fine.


I then recalled the burping methods used to remove air bubbles from my Q45 a decade ago and I believe I've finally removed the bulk of it. I parked on an angle with the engine facing up, placed a funnel over the filler neck, and goosed the throttle several times to force the bubbles out while topping off the coolant on occasion.

So far, it appears that my mechanic's theory was right -- it just needed additional bleeding and burping. We'll see what happens after some long drives.

This process is so much simpler on cars with bleed screws and pressurized expansion tanks.




I'm about to drive the Subie home and test it out. Could I still have a head gasket issue despite passing the block test? I've read on Subaru forums about people replacing their t-stats and radiators and water pumps and still having HG issues weeks later.

This car is intended for resale and there's a nice lady who is interested in buying it at my asking price. However, I told her I wasn't comfortable selling it unless I was 100% sure that it was in perfect working order. I would rather take a loss and wholesale it as-is than band-aid it and leave someone stranded months later.

[Jesda]

Just got home from a 15 mile, 20-minute drive. It behaved better this time. It seemed okay when I got off the highway but after a few blocks the temp needle started to creep as I pulled into my complex.

Here's where the needle was just before I shut it down:

[nissangirl74]

Any oil in your radiator overflow?

did you / mechanic test the thermostat?

[Ace2cool]

I was gonna say either thermostat or water pump. Other than that, burping the radiatorin a Subie should be done while on a decently generous uphill slope so you can get the air bubbles out of the heater core.

[Jesda]

No oil/coolant mixing
No milky oil cap
Exhaust doesnt seem to have any kind of sweet smell

Havent pulled and tested the t-stat yet. The calsonic radiator cap appears to be doing its job and allowing coolant to flow into the overflow reservoir, but I suppose it couldn't hurt to pick up an OEM cap and replace that.

[frapjap]

Set it on fire.
Blame on 'punk a** kids'
?????
PROFIT

[WDRacing]

How difficult is it to access the tstat? Might as well change it out if you're going to test it, assuming it's not expensive anyway. I've always parked my vehicles on ramps when bleeding and filling.

Props for not being a douche and unloading it without having a known fix. Rare these days.

[gwoods]

tstat don't bother testing it just replace it.

[hannibal]

I agree on the t-stat. Seems like it only opens when it feels like it.

[gwoods]

I am guessing its stuck partially open. The radiator is a heat exchange, if the fluid never has a chance to stay in the radiator and cool it will gradually get hotter and hotter. 155k miles is a lot to ask of a tstat.

[MinisterofDOOM]

I agree with the thermostat diagnosis. I bet it's a PITA to get to on a flat-four though.

[Dattebayo]

Do subies need the heater core open in order to bleed out completely? The last time I had to do this in my car, I had to turn the heater on full for a few minutes before the bleed and leave it on when I shut the car off so the heater valve would be open all the way.

[float_6969]

Sounds like a sticky thermostat to me.

[alms24sebring]

I believe the thermostat on that car is easily accessible under the car. Put it on ramps and take the skidplate off, at the end of the lower rad hose into the block cant miss it. Just replace it and let it take its time bleeding. If its overflowing, I found that turning it off for a minute then starting it up with the gas to the floor forces alot of air out. Just let it take its time and just squeeze the upper hose to bleed the rest out.

I see people at work that dont turn on the heat when doing coolant work. I guess it wouldnt matter because it wont drain if its closed to begin with. I always do just to make sure coolant is flowing, its a good gauge. If theres no heat and its at temp, theres an air bubble.

[Jesda]

Heat was on during the bleed.

I'll have my mechanic install a new OEM t-stat. That boxer looks like a PITA.

Thanks!