I just installed a used  radiator in my 98 legacy outback and it will run at normal temp. for awhile then it will start to overheat. it will push all the antifreeze into the resivor. if i release the pressure on the cap it will start to run normal again.every once in a while i lose heat for about  1 or 2 minutes and the antifreeze seems cold not hot. ive been told it sounded like a air bubble in the system any ideas?

It's almost certainly a blown headgasket. If you look in the overflow tank you'll probably see bubbles.

Edited November 22, 201411 yr by 987687

I'm not seeing any bubbles and not seeing anything in my oil or in my tranny fluid

Why did you replace the radiator? Was it overheating/acting up before the used radiator was put in? Is the radiator cap good, is there any gunk or garbage underneath the rubber gasket? It is easy to trap air in the system and hopefully that's it ... but the overflow filling up and the losing heat does sound like a possible HG issue ... and that is the era known for the exhaust blowing into coolant HG failure mode.

Edited November 22, 201411 yr by porcupine73

Head gasket is a possibility but if your heater is going cold it's because it's low on coolant. You've got air in the system still. I had similar symptoms after doing an engine swap in a 96 Outback last week. There's a vent plug on the opposite side of the radiator (Square plastic cap) Pull that and fill the radiator to the brim. Run the motor and as it warms, squeeze the upper radiator hose to push extra air out of the system. Let it run until it starts heating up again. Be sure the coolant reservoir is full so the system can suck in extra fluid. Took me 3 times and all was well. Heat stayed hot, temp gauge never even hits the halfway mark.

on my old radiator one of the hose inlet/outlet tubes cracked and pretty much desinagrated. forgot to add did have another subaru radiator in it before this one, it worked and didnt have any problems with it other than i couldn't secure it down right(needed it to just work so i could get to work)

are you talking about the plug with the screw head on it?

yep. Square on top but has a phillips head. Just lets air vent out better when you fill by the radiator cap.

ok I'll  try it in a while

Having a similar problem with my 03 Baja. On a couple of occasions last month the temp gauge rose quickly to the max. Stopped immediately and

let engine cool. Overflow canister was full to top. Radiator hoses and cap were not extremely hot to touch. Added a quart or more of coolant to radiator

and was able to continue driving. Fluid in the overflow was never drawn back into the radiator after car was parked and completely cold. Put car in the shop,

Nothing determined wrong. Replaced the radiator cap and rubber hose from top of radiator to overflow canister. The hose did has some cracks and deterioration on

the end. Drove the car several more days with no overheating issues; although the canister remained above normal levels. Added coolant and/or water to

radiator on several occasions. Never any loss of heat from the heater. Week before last made a 400 mile plus trip without incident. One way drive however.

Shortly into my return trip the temp gauge pegged out again starting the upgrade of the western VA mountains. Let the engine cool again, added more 

coolant and made a immediate u-turn back to my starting point. Had to leave the Baja at a repair job and get a rental to get back home. The car has 117,000

miles. Had been well maintained and serviced. Around 100,000 miles; new timing belt and water pump. At about 108,000; new head gasket. Old gasket didn't

blow, but was seeping a consider amount of oil on the exhaust manifold. Repairs to the car are on stand-by. Mechanic tried a new thermostat. No difference

in condition. Could sit and idle all day without overheating. Hit the incline of a mountain road and the needle hits the max. He also did a flow test on the radiator

and no restriction found. The mechanic there is convinced it is the head casket.  A new head gasket again is a costly proposition.

Most jobs are warrantied for 12 months or 12,000 miles - you're still within the warranty of most repairs.

 

probably headgasket - they can test for hydrocarbons in the coolant.

 

the key isn't repairing the engine - but repairing it properly.  all headgasket jobs are not equal - particularly on an engine with known issues and weaknesses:

1. use Six Star or Subaru Turbo EJ25 headgaskets only

2.  resurface the heads

 

most places don't do either of those so a repeat failure isn't that surprising. 

update on the overheating got it fixed as far as i can tell . I couldn't get to  stop overheating so my friend told me the only way he got the air out of his was to run it until it got  hot and shut it down and lett it cool down till its cold.by some miricle it worked , just got done taking it on a 40 mile drive up hills and horsing on it and it never came over the middle of the gauge.thanks for all the input guys

update on the overheating got it fixed as far as i can tell . I couldn't get to  stop overheating so my friend told me the only way he got the air out of his was to run it until it got  hot and shut it down and lett it cool down till its cold.by some miricle it worked , just got done taking it on a 40 mile drive up hills and horsing on it and it never came over the middle of the gauge.thanks for all the input guys

Do you mean running it with the radiator cap off?

with the cap on to get it to start to overheat and then shut the car off 

No, that will do nothing for burping the system. The air must be trapped somewhere else or its a head gasket. There is a proper way to burp the system, and it can't be done with the cap on.

 

The bleed screw is there for a reason, use it. You can burp the system by leaving the cap off and running it till it gets up to temp, that should let the air escape, then put the cap back on and make sure there is fluid in the resivour so as it cools it will suck fluid back into the radiator

there may be a proper way to it which i understand what your saying, all i can say is that is what i did and it worked can't explain why but it did. there is no evidence of a head gasket problem there is no coolent in my oil or in the tranny,no signs of leaking anywhere on the motor and the exhaust has no moisture comming out the exhaust or no smell of burning coolant. all I can say is it hasnt overheated since

Coolant almost never mixes with oil when headgaskets go on these engines, it blows exhaust into the cooling system. The reason it overheats and you lose the heater is because a pocket of air forms in the thermostat, it closes, the pump cavitates, and coolant stops getting pumped through the heater core.

 

I'm not sure why you'd have coolant in the transmission, that only happens when the cooling tubes in the radiator go bad which is rare and has nothing to do with headgaskets.

Believe me I've been through over heating problems with my legacy and I would think I fixed it and then it would act up again.

There is no way that just over heating it and shouting it off is going to get the air out of the system

And Subaru's don't burn coolant when the head gasket goes out they push air into the coolant so it won't smoke

Edited November 24, 201411 yr by mikaleda

The only thing to accomplish with this method is to add coolant after doing so.

I just installed a used  radiator in my 98 legacy outback and it will run at normal temp. for awhile then it will start to overheat. it will push all the antifreeze into the resivor. if i release the pressure on the cap it will start to run normal again.every once in a while i lose heat for about  1 or 2 minutes and the antifreeze seems cold not hot. ive been told it sounded like a air bubble in the system any ideas?

After reading the entire thread, I would say most likely cause is head gasket.  The '98 2.5's were notorious for blowing head gaskets. 

They could blow at any time from recently replaced to over 75K miles. Never was very predictable on the "when" part.

The most reliable solution I've found anywhere is to replace the entire 2.5 engine with a 2.2. Only real side effect is the check engine light stays on because the 2.2 has no EGR system.

I'm still not completely convinced its a head gasket i did however get some more air out of the system and replaced the radiator cap . there hasn't been any repeat overheating since it is omething imkeeping my eye on

If there's air getting in the system, hate to say it, probably HG. They start slowly so you keep thinking it's something else.

I'm still not completely convinced its a head gasket i did however get some more air out of the system and replaced the radiator cap . there hasn't been any repeat overheating since it is omething imkeeping my eye on

 

if you had zero overheating and replaced the radiator and had burping issues - yeah it's unlikely the headgasket and probably just air in the system if what you said is accurate. 

 

though i would be very careful letting it run hot as it seems like it has - having lost heat, etc usually means it's above nominal temps.  you don't want to tempt an EJ25D to blow headgaskets.

 The car has 117,000 miles. Had been well maintained and serviced. Around 100,000 miles; new timing belt and water pump. At about 108,000; new head gasket..

 

Subaru and most legitimate shops offer a 12 month 12,000 mile warranty - that headgasket repair should be warrantied. Find a way to get it home and have it fixed for free.

 

Given this engines propensity to blow headgaskets you don't just do 'an average headgasket replacement' - you want quantifiable, engine specific expertise.  Which means this:

1. Use Subaru Turbo headgaskets or Six Star headgaskets - installing Subaru's "updated" gasket for that application is the same gasket failing in other Subaru's...that makes no sense on such an expensive repair.

2.  Resurface the heads - no matter what.  There's no need to pressure test or mic or measure or valve job - just resurface them, they never crack, warp, or fail (or if they do it would be to catastrophic abuse)

we did reburp the system recently and decided to put on a new cap while at it haven't had any problems lately