Is it a water pump? Blockage? Radiator? (2002 Subaru WRX)

[Vicarious_Lee]

So my car started overheating tonight. Not severely, but I caught the gauge going near the top. Oddly enough, the engine never felt particularly hot once I got the hood open. It was inconsistent with driving or idling. Acceleration caused it to get hotter, deceleration had it cool down.

Other symptoms:

Did not go away with addition of water.

Fans are both running at idle.

Heater on full-blast into the car would occasionally stop heating at random and then get hot again.

New radiator fluid, hoses, belts, and tensioner put on last year.

What do y'all think?

[hatchtrikk]

Was the radiator low on fluid?

May be the head gasket

How many miles does it have?

[Confucius]

Hmm, not sure what that'd be, but I'd try swapping out the thermostat and doing a block/radiator flush as a matter of course.

Are you losing coolant? How's the oil look?

[hatchtrikk]

Ooh thermostat. Good call! There are only so many components that affect engine temp. If you remove the thermostat and put in in boiling water, you check function.

Start with the cheap stuff first, then work your way up.

[Vicarious_Lee]

Was the radiator low on fluid?

May be the head gasket

How many miles does it have?

Reserve tank is dry. It tends to do that over time because the turbo has a cool-down method that basically boils off the fluid around the bearing and draws more radiator fluid up to it through convection (or something) when the car is turned off. It's always lost a little bit of fluid over time since new.

It's only got 82K on it.

Hmm, not sure what that'd be, but I'd try swapping out the thermostat and doing a block/radiator flush as a matter of course.

Are you losing coolant? How's the oil look?

Could be the T-stat but doesn't the heater core bypass the thermostat and take off from the block? The heater stops working, too when the temps rise. That's why I'm thinking it could be the water pump.

Oil's finally getting a little gasoline smell to it, but it's still not burning any and the oil quality looks just fine.

Ooh thermostat. Good call! There are only so many components that affect engine temp. If you remove the thermostat and put in in boiling water, you check function.

Start with the cheap stuff first, then work your way up.

Might do that, or I might take it to the stealership anyway. The problem is that it needs a few things done with gas lines as well anyway. If I pull the T-stat and that's not it, then I have to seal it up, fill it up, and drive it to the shop anyway.

Hey thanks for all the help, though. I just realized that it would be prudent to pull the T-stat anyway before driving it.

[KJ4VOV]

Hey thanks for all the help, though. I just realized that it would be prudent to pull the T-stat anyway before driving it.

Don't just pull it and seal it back up. If you do, you'll just have to do it again to put in a replacement anyway later on. Why do the work twice? Replace it with new while you have it open and be done with it.

And, if you're thinking of just leaving it out, that's not a good idea. For one thing, you'll have very little heat in the winter, and you'll be running the engine too cold all the time, which will seriously affect your emissions and fuel economy.

[Vicarious_Lee]

Hey thanks for all the help, though. I just realized that it would be prudent to pull the T-stat anyway before driving it.

Don't just pull it and seal it back up. If you do, you'll just have to do it again to put in a replacement anyway later on. Why do the work twice? Replace it with new while you have it open and be done with it.

And, if you're thinking of just leaving it out, that's not a good idea. For one thing, you'll have very little heat in the winter, and you'll be running the engine too cold all the time, which will seriously affect your emissions and fuel economy.

Yeah, no definitely not that. There was talk back in the day of running a colder 160-degree t-stat in our WRX-es for more power, but some of the engineering types thought that it would contribute to accelerated cylinder wear like it did when racers did that to the old 5.0 Mustang motors.

The question now is this: Do I go get a T-stat tomorrow and just replace it on a gamble because it's cheap, do I test-drive it to see more about the problem, or do I just take it in anyway?

I think I'm gonna replace the thermostat first, since it seems to be a blockage-based, on-again/off-again problem. However, I could've sworn that our cars' thermostats fail open.....

EDIT: OOH OOH SCHMIDDLEY-BOO!!! I just had a thought!

It has to be the T-stat. The radiator wasn't hot after the 5-minute drive home, and the overflow tank still had just distilled water in it without a trace of antifreeze mixed in.

Will change thermostat tomorrow and hope for the best.

[KJ4VOV]

Hey thanks for all the help, though. I just realized that it would be prudent to pull the T-stat anyway before driving it.

Don't just pull it and seal it back up. If you do, you'll just have to do it again to put in a replacement anyway later on. Why do the work twice? Replace it with new while you have it open and be done with it.

And, if you're thinking of just leaving it out, that's not a good idea. For one thing, you'll have very little heat in the winter, and you'll be running the engine too cold all the time, which will seriously affect your emissions and fuel economy.

Yeah, no definitely not that. There was talk back in the day of running a colder 160-degree t-stat in our WRX-es for more power, but some of the engineering types thought that it would contribute to accelerated cylinder wear like it did when racers did that to the old 5.0 Mustang motors.

The question now is this: Do I go get a T-stat tomorrow and just replace it on a gamble because it's cheap, do I test-drive it to see more about the problem, or do I just take it in anyway?

I think I'm gonna replace the thermostat first, since it seems to be a blockage-based, on-again/off-again problem. However, I could've sworn that our cars' thermostats fail open.....

I've seen a few "fail open" stats that didn't, so it's a possibility. One thing I'd suggest, before anything else, is check the tension on your serpentine belt. I've seen tensioners that freeze up and "look" okay, but not provide enough tension to stop the belt from slipping, and since the water pump pully is often times smooth (runs on the back of the belt) it's the first one to slip, often well before you start noticing a voltage or amperage drop from the alternator when it starts slipping.

[Vicarious_Lee]

Hey thanks for all the help, though. I just realized that it would be prudent to pull the T-stat anyway before driving it.

Don't just pull it and seal it back up. If you do, you'll just have to do it again to put in a replacement anyway later on. Why do the work twice? Replace it with new while you have it open and be done with it.

And, if you're thinking of just leaving it out, that's not a good idea. For one thing, you'll have very little heat in the winter, and you'll be running the engine too cold all the time, which will seriously affect your emissions and fuel economy.

Yeah, no definitely not that. There was talk back in the day of running a colder 160-degree t-stat in our WRX-es for more power, but some of the engineering types thought that it would contribute to accelerated cylinder wear like it did when racers did that to the old 5.0 Mustang motors.

The question now is this: Do I go get a T-stat tomorrow and just replace it on a gamble because it's cheap, do I test-drive it to see more about the problem, or do I just take it in anyway?

I think I'm gonna replace the thermostat first, since it seems to be a blockage-based, on-again/off-again problem. However, I could've sworn that our cars' thermostats fail open.....

I've seen a few "fail open" stats that didn't, so it's a possibility. One thing I'd suggest, before anything else, is check the tension on your serpentine belt. I've seen tensioners that freeze up and "look" okay, but not provide enough tension to stop the belt from slipping, and since the water pump pully is often times smooth (runs on the back of the belt) it's the first one to slip, often well before you start noticing a voltage or amperage drop from the alternator when it starts slipping.

Oh thanks. But check my update for why I'm pretty sure it's the T-stat. Also, I just had that belt replaced with a high performance STi belt about a year ago with new metal tensioner pulley.

It totally still could be the water pump, and if it is, I'm only going to be out time and a little bit of money. I dislike taking my cars to a mechanic, so it's worth it to me to try replacing the thermostat myself first.

Thanks for everyone's help!

[hatchtrikk]

Let us know if that was the problem.

Good luck!

[williaty]

Disclosure: I am a Subaru specialist mechanic, but I am not your Subaru specialist mechanic. Seek local professional help. I'm not responsible for what happens if you actually listen to the internet!

I own a independent Subaru speciality shop. I see 2-3 Subarus a month with the specific symptoms you mention. Yes, it's your headgasket. The EJ25-series engines are infamous for how shitty their headgaskets are. If you are an advanced shadetree mechanic and are super anal about detail and cleanliness, you can do this service yourself with the help of the factory service manual. There's a couple of serious sticking points, such as removing the cam sprockets, but nothing that's absolutely impossible for the non-professional. If you're not 100% sure that this is within your means, then take it to a Subaru specialist. It is absolutely critical that the shop you choose specializes in Subarus! If it's just a general independent mechanic or even a import specialist mechanic, there's so many unique quirks to a Subaru engine that they'll almost certainly fuck it up. In fact, I'm accepting a nearly $3,000 check from a guy tomorrow because a shop that had the car before me screwed up the headgasket job and basically ruined the motor.

But let's pretend that Subarus weren't well known for shitting their headgaskets and we'll rule out other parts it could be.

1) It's not the ECT sender. The ECT sender could cause the fan to run all the time but it can't cause the heat to stop blowing nor can it make coolant disappear.

2) It's not either of your radiator caps. When the upper one fails, it just causes the lower one to fail. When the lower one fails, it floods the overflow tank, not sucks it dry.

3) It's not your thermostat. While a thermostat could cause elevated engine temps if it stuck shut, the heater coolant circuit bypasses the t-stat and will run hot regardless of what the rest of the system is up to.

4) It's not your water pump. Subaru water pumps fail only in 1 of 2 ways. Either the impeller separates from the axle (which causes a god-awful noise) or they seize solid, which promptly destroys the engine. The EJ205 you've got is an interference engine and the water pump is driven by the timing belt. Any hiccup with the water pump and the valves are sent crashing into each other and the pistons.

That concludes a round trip tour of your cooling system. It's your headgaskets. BTW, you have also already driven the car too long with a headgasket leak and your cylinder heads WILL need torn down and machined flat again because you've warped them.

You should always do both headgaskets at the same time. It's cheaper to do both at once than one on each of two separate occasions. If one has failed, the other IS about to go. If you're auditioning a shop, you want to ask them two questions to figure out if they know what the hell they're doing or not. First, ask them if they do the service with the engine in the car or out of the car. Shops trying to cut corners on flat rate time will do it with the engine in the car. You CANNOT do a good job with the engine in the car. Shops concerned with doing a high-quality repair will remove the engine from the car. Second question to ask is what kind of headgaskets they'll be using. If the answer is anything other than Subaru brand ones or Cometic, run for the hills. Even if they say "OEM", pin them down for a straight answer as to wither or not they're buying them from a dealership so they'll have a Subaru of America part number sticker on them. If they say Cometic, tell them you're not building a racecar and just order the Subaru ones.


NOTE: It's also absolutely critical that you use a Subaru thermostat, thermostat gasket, and water pump gasket. I would conservatively estimate that using a non-Subaru part for any of those three things results in at least a 70% "come back" rate. Good shops won't use aftermarket or "OEM-equivalent" parts for that because it ends up costing them more money to use the cheap part when they have to do the service a second time.

[williaty]

Note that the above assumes your radiator itself isn't leaking (Subaru radiators are notorious for the endcaps cracking and leaking at about the age your car is). I am assuming this because, when the rad starts leaking, it drips on the exhaust manifolds and crossover pipe and your car starts smelling like pancakes. Since you didn't report breakfast-based olfactory anomalies, I'm ruling that out as well.

[Vicarious_Lee]

Well fuck me sideways, then.

Listen, I cannot thank you enough for laying down such valuable expertise for me. Like, if I can buy you a ZS membership remotely I will, but you're basically telling me that this little mole I'm thinking of getting burned off because it's starting to bother me is, in fact, metastatic cancer.

I've owned this car 9 years, and have been active on the Subaru boards for longer than that. This headgasket problem is the first I've heard of. Roxy has been problem-free for my entire ownership, but for problems I've caused upgrading her. I've got the EJ205 with original turbo on a stage II reflash with exhaust and some other minor things. Driven hard always, but never raced.

There's no pancake smell (had that with an old '86 Ford Crown Vic), and no indication whatsoever that I'm burning antifreeze through the cylinders. I can't fathom that what you're saying is going on in my car based on what I know, but I'm a rank amateur at this.

I have a lot of questions, and this is a lot to digest, and I need to go to bed, but can I ask you this:

If I've thrashed my rings and walls, I guess now wouldn't be a bad time to get a 2.5 short block replacement? If this is a total teardown, and I've always thought of upgrading anyway, might I just do it, then?

There's no oil, no smoke, no nothing otherwise. I mean, the oil smells a bit of gasoline (Amsoil like the pretentious prick I am), but it's not even burning that. Not even a half-quart at over 5,000 miles.

What I'm saying is: Give me some options, doc! Surely this is not terminal!

I'ma replace the T-stat tomorrow before taking it in, but if I have to, I'm going to thankfully use your knowledge when I do.

Damn, you just kicked my puppy tonight, but I appreciate you taking the time to do so.

[williaty]

Well fuck me sideways, then.

Yeah, tell me about it. Last year, I had my engine out once a month for 5 months in a row because I was doing R&D on some prototype engine internals. Then my HGs went (it was time). Then about 3 months after that, I spun not 1 but all 4 rod bearings. Life is hard for an engine that's a daily driver, a racer, and a development mule!

Listen, I cannot thank you enough for laying down such valuable expertise for me. Like, if I can buy you a ZS membership remotely I will, but you're basically telling me that this little mole I'm thinking of getting burned off because it's starting to bother me is, in fact, metastatic cancer.

I was honestly unaware ZS had memberships

So, right now, it's more like you've detected a cancer at an early stage. A little earlier (before you got heating symptoms) and you could have just burned it off (aka HG job with no need to machine the heads). If you act quickly, you can only have to go through chemo (HG service with heads milled). However, if you delay, you're going to end up losing limbs in surgery (spinning a bearing). The big thing is to not drive the car before you get it fixed. The pockets of hot/cold are actually bubbles of air traveling though the cooling system. Air is not good at carrying heat away from the metal bits. This leads to localized areas of extreme heat. This warps things. The longer you drive the car with a HG leak, the worse the warping. It's possible to warp things beyond the limit of repair. Additionally, you will eventually end up with coolant in the oil, since the HG is the only thing that separates the oil from the coolant. Coolant is a shitty lubricant. Once you cross a line in terms of coolant contamination, you'll spin a bearing. Endgame for your shortblock at that point.

I've owned this car 9 years, and have been active on the Subaru boards for longer than that. This headgasket problem is the first I've heard of. Roxy has been problem-free for my entire ownership, but for problems I've caused upgrading her. I've got the EJ205 with original turbo on a stage II reflash with exhaust and some other minor things. Driven hard always, but never raced.

Search for "headgasket problem" on NASIOC. Lots of rage.

If I've thrashed my rings and walls, I guess now wouldn't be a bad time to get a 2.5 short block replacement? If this is a total teardown, and I've always thought of upgrading anyway, might I just do it, then?

At this point, you have no reason to think that the shortblock (engine block, crank, rods, pistons, and bearings) has been damaged. For monetary reasons, I'd suggest not upgrading at this time. If you happen to spin a bearing (will sound like something between someone beating on your engine with a ball peen hammer and a diesel VW car), then, yeah, just buy a new factory 2.5L shortblock, a factory Master Gasket Kit, and then have your heads milled and put it all back together. You'll need a custom tune at that point, btw.

[williaty]

Oh, I think somewhere that I forgot to quote and answer, you wondered about where the coolant is going. One of two things is happening (Subarus love to do both). One option is combustion gasses are escaping into the coolant jacket, pressurizing the coolant, and forcing it into the overflow. Since your overflow is dry, this is unlikely, but you actually wouldn't be the first guy who had a HG leak and a hole in the bottom of his overflow tank at the same time Second option is that the pressurization of the cooling system is forcing very small amounts of coolant into the cylinder during the intake stroke (cylinder under vacuum). It may only be pulling in a few tenths of a mL each stroke, but that adds up at 3kRPM. Since the coolant is constantly flash boiled, you'll never notice anything except *maybe* the exhaust steams for a minute or two longer in the morning. This is more likely what's happening to you. Nice thing is that the constant steam-cleaning will make it so you don't have as much carbon to clean off your piston and head

[Vicarious_Lee]

Well, I got a thermostat for 5 bucks and am gonna just go on a prayer right now. We'll see if the other one is sticking. I still can't figure out how a head gasket would cause the heater to only intermittently work. Also, you said this:

BTW, you have also already driven the car too long with a headgasket leak and your cylinder heads WILL need torn down and machined flat again because you've warped them.

There's no indication that my rings are bad. In fact, I'm 5,000 miles on an oil change and it hasn't burned a drop. You sure? I just started noticing the heat?

Should I show up to the dealership with cometic gaskets? Unless you know someone close to Houston that can do it, I'm just not going to take any chances with rebuilding the motor.

Thanks for all your help, man. I appreciate it.

[grennels]

4) It's not your water pump. Subaru water pumps fail only in 1 of 2 ways. Either the impeller separates from the axle (which causes a god-awful noise) or they seize solid, which promptly destroys the engine. The EJ205 you've got is an interference engine and the water pump is driven by the timing belt. Any hiccup with the water pump and the valves are sent crashing into each other and the pistons.

Are ALL Suby water pumps driven by the timing belt. Seems like a pretty shitty
idea.

[williaty]

I still can't figure out how a head gasket would cause the heater to only intermittently work.

The HG leak is letting air into the cooling system. When the air goes through the heater core or a bubble temporarily blocks flow through the heater core, you get no heat.

Also, you said this:

BTW, you have also already driven the car too long with a headgasket leak and your cylinder heads WILL need torn down and machined flat again because you've warped them.

There's no indication that my rings are bad. In fact, I'm 5,000 miles on an oil change and it hasn't burned a drop. You sure? I just started noticing the heat?

Head flatness has nothing to do with piston rings. Complete different parts of the engine.

Should I show up to the dealership with cometic gaskets? Unless you know someone close to Houston that can do it, I'm just not going to take any chances with rebuilding the motor.

I wouldn't use the Cometic gaskets unless you're building a race engine. They cost too much and are a pain in the ass to work with. Just use the Subaru gaskets unless you're starting from a race-built shortblock.

[williaty]

Are ALL Suby water pumps driven by the timing belt. Seems like a pretty shitty
idea.

All of the Subaru water pumps I've had to work with are driven by the timing belt. It's actually not uncommon from makers other than Subaru as well.

[Vicarious_Lee]

I still can't figure out how a head gasket would cause the heater to only intermittently work.

The HG leak is letting air into the cooling system. When the air goes through the heater core or a bubble temporarily blocks flow through the heater core, you get no heat.

Also, you said this:

BTW, you have also already driven the car too long with a headgasket leak and your cylinder heads WILL need torn down and machined flat again because you've warped them.

There's no indication that my rings are bad. In fact, I'm 5,000 miles on an oil change and it hasn't burned a drop. You sure? I just started noticing the heat?

Head flatness has nothing to do with piston rings. Complete different parts of the engine.

Should I show up to the dealership with cometic gaskets? Unless you know someone close to Houston that can do it, I'm just not going to take any chances with rebuilding the motor.

I wouldn't use the Cometic gaskets unless you're building a race engine. They cost too much and are a pain in the ass to work with. Just use the Subaru gaskets unless you're starting from a race-built shortblock.

I hate ur face for the sense you're making right now. And I get it, heat warped the heads, not the cylinders. Nevermind I see where your'e coming from.

Well, time to just BOHICA this on up to the dealership. I need those fuel lines under the intake replaced anyway for the last few years. Get that cold start fuel smell as time goes on.

Well, thank you so much for all your help. I'll keep the thread updated.

Hey Will, are the heads going to need to be re-built or just milled? Should I consider upgrading heads?

[KJ4VOV]

I love it when a true expert shows up and lays it on the line.

I'm a good mechanic (ASE certified about 17 years ago - but out of the trade for a decade now), but with very little experience with Subies, so I'm glad Will dropped into this thread to steer it straight. And dang... how did I ever forget about Subies water pumps being timing belt driven? I've changed belts on a few in the past, so I should have remembered. It sucks becoming an old fart.

[Vicarious_Lee]

And a big NOPE on new heads. Only ones I can find are Cosworths and they're for the 2.5 block anyway. I called the dealership and looks like we're gonna need new head gaskets.

Thanks again for laying down the PWN for me, Will.

EDIT: It's the head gasket.

[Oneswunk]

Damn looks like wills got you covered. Good luck bro, ill be following.


Eta, ballz that sucks them.

[williaty]

Hey Will, are the heads going to need to be re-built or just milled? Should I consider upgrading heads?

To allow the heads to be milled, the valve springs, keepers, retainers, seats, seals, and valves will have to be removed from the head. That counts as a full rebuild, really.

There really aren't heads that are a significant upgrade. Well, there's some "for race use only" stuff, but the reliability is crap and you have to have huge supporting mods to pay off. We did upgraded (PnP+cams+secret sauce) heads for one of the TA cars, which then made 400lbf-ft +/-10% from 3800RPM to 7200RPM. That was a quick car to drive! For a street car, just re-use the stock heads.