Had a leaky water pump on my 97 impreza. Replaced it with thermostat, coolant flush, timing belt, and bearings. Ran great for a week. Then all the sudden, it started overheating. No leaks, fans are working. I was convinced it was dud thermostat. Replaced it with another brand, yes I put it in the right way. Still overheating. Replaced radiator and hoses with another coolant flush. Same thing. It will idle all day long and will drive just fine for a while. It seems to overheat while under load going up hill or high speeds. Did I get a dud water pump? Or the is the tensioner weak? What else is there? It is weird how it is intermittent and common to overheat on hills, I am thinking the tensioner is weak ans slipping on the water pump. Thoughts?

 

Wes

Had a leaky water pump on my 97 impreza.

how long was it leaking and how many times did it overheat?

any previous work done before all this?

how many miles?

 

next time it's running hot turn the heat all the way up in the cabin on high for a few minutes - after the initial really hot air does it eventually cool down after a couple minutes?

 

make sure the coolant is properly burped of air bubbles, these engines are notorious for getting air bubbles in them and being hard to bleed. nose up keep filling while engine warms up with radiator cap off. some models have a plastic bleeder screw on the passengers side of the radiator.

 

thermostat should be Subaru or the XACTA OEM style, aftermarkets look like toys compared to the OEM tstat. But at this point with this much work it appears that's not the issue here.

 

It seems to overheat while under load going up hill or high speeds.

sounds like reduced cooling, clogged radiator (which you already replaced), or reduced flow?

 

headgasket sounds plausible but would really only happen if the car has been overheated on this engine.

I cranked the heater to hot, nice and warm constantly. Even it was clogged it wouldn't cause this issue. I doubled checked the burping as well, all good. I did a compression test as well, I was concerned that I warped the heads or blew the gasket when it got hot. Compression tested good and even. It has 249k plus on it, speedometor is broken. I would estimate probably 260 or 270k now. I wouldn't think the water pump would be intermittent, I am almost convinced it is the tensioner slipping. Who knows it could.be OEM.

Check the coolant to see if exhaust gases are getting into it. Even though you checked the compression it sounds like a gasket leak to me. If that checks ok then I would have to think the radiator would be suspect.

I am almost convinced it is the tensioner slipping. Who knows it could.be OEM.

Is it an original tensioner, new or old style?

 

Good call on the tensioner, sounds like something to look into. The new style tensioners make a very loud and notable knocking noise when they fail usually...but there are probably multiple failure modes.

 

I cranked the heater to hot, nice and warm constantly. Even it was clogged it wouldn't cause this issue.

not about clogging, classic EJ headgasket problems include pushing exhaust gases into the coolant and preventing proper flow. if the heater blows hot and then gets cool - that is classic headgasket signs. doesn't necessarily rule it out though.

 

EJ22's don't have headgasket issues like the EJ25 but if it's ever been overheated or compromised they can exhibit similar issues.

 

compression and leak down tests aren't useful in EJ engines. every single EJ25 from 1996 - 2010 passes a compression test when it's headgasket first starts to fail.

EJ22's don't have headgasket issues like the EJ25 but if it's ever been overheated or compromised they can exhibit similar issues.

 

NOT TRUE............I had a 91 EJ22 in a Leggie that blew a head gasket. Yes, the EJ22 infrequently can blow a head gasket, but not as often as in the EJ25, gen one, but it does happen.

Is it an original tensioner, new or old style?

 

Good call on the tensioner, sounds like something to look into. The new style tensioners make a very loud and notable knocking noise when they fail usually...but there are probably multiple failure modes.

 

not about clogging, classic EJ headgasket problems include pushing exhaust gases into the coolant and preventing proper flow. if the heater blows hot and then gets cool - that is classic headgasket signs. doesn't necessarily rule it out though.

 

EJ22's don't have headgasket issues like the EJ25 but if it's ever been overheated or compromised they can exhibit similar issues.

 

compression and leak down tests aren't useful in EJ engines. every single EJ25 from 1996 - 2010 passes a compression test when it's headgasket first starts to fail.

 

After removing the cover, the belt doesn't feel as tight as it is suppose to be, but I have nothing to compare it to except memory and common sense lol. I see what you mean on the heater core now, but it was constant warm. Very interesting good info, I appreciate your time. I will continue to investigate.

EJ22's don't have headgasket issues like the EJ25 but if it's ever been overheated or compromised they can exhibit similar issues.

 

NOT TRUE............I had a 91 EJ22 in a Leggie that blew a head gasket. Yes, the EJ22 infrequently can blow a head gasket, but not as often as in the EJ25, gen one, but it does happen.

 

How many miles did it have?

I don't think he was saying they never fail, every engine out there is vulnerable. It is more vulnerable in the ej25.