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wrx54 02-03-2011 12:02 AM

Overheating after clutch install. Help!
So after several months of subaru withdrawal, I finally tore the guts out of my 2002 WRX Wagon in order to inspect a clutch failure.

I briefly entertained the idea of pulling the engine forward and so began the job by draining and removing the radiator. I then thought better of this and pulled the drive shaft and tranny out by the conventional method. After replacing a shredded throwout bearing, I reassembled downpipe, driveshaft, and heatshields, reconnected wires and airflow sensor, and reinstalled the intercooler.

That left the simple task of reinstalling and refilling the radiator.

Finally, I had coolant topped off after running engine and heater. Job done. It was time for a test drive.

5 miles of exuberance on a job well done and the familiar heart in stomach acceleration, then a sudden heat stroke! I nursed it back to the garage and topped off more fluid, burped the line, etc. Repeat; 5 miles then, bam! Busted radiator!

I waited impatiently for a radiator repair, then reinstalled and went through unusual amounts of fluid. Every 5-10 miles the same problem occurred.

So I pulled it all back out and took out the waterpump and termostat. The waterpump looked fine, but I replaced the thermostat and all hose segments on the pump then finally put everything back together.

5 miles and again same problem. *$%#! WTF?

Temperature runs normal on these drives and goes up rather suddenly. Before, I thought I had been loosing water, but now it just seems to dump into overflow tank, leaving the reservoir empty after a drive. I've observed a bubbling/boiling sound emanating from the return line through the turbo. Is this normal? Does this return line pass water through the turbo?

What's going on??

wagonracer 02-03-2011 07:10 AM

Sounds like you still have air in the system to me. Did you check the seals on the cap ?

wrx54 02-03-2011 11:45 AM

Yes, the cap seals are okay. Can anyone recommend a thread on the proper way to burp the system?

Also, does the coolant return line by the turbo somehow interact with the turbo, or does it just happen to attach in this area?

pzr2874 02-03-2011 12:45 PM

Here's something for you :


As far as the return line... Do you have a stock turbo still in the car ?

If so, the turbo is water AND oil cooled.... So, yes.

And another :


wrx54 02-03-2011 01:18 PM

Thanks guys, I'll give burping another try, but this procedure is basically what I have been doing. Except for step 4 I go on a short drive, is that bad?

1) Fill the coolant resevoir (plastic bottle) to the fill line (put cap on)
2) Fill the Turbo Coolant Reevoir (small metal right in front of turbo) (put cap on)
3) Start car and turn on heater (high)
4) Hold RPM's at 3000 for 10 minutes ( even if temp = H)
5) Turn engine off and leave key to ACC (keep heater on)
6) Let engine cool to "C"
7) Repeat steps 1-6 until no coolant is required to fill resevoirs

Paul, I wasn't sure the turbo was water cooled, thanks. I've been wanting to associate the problem with heavy acceleration, but I can't confirm that yet.

man show 02-03-2011 01:46 PM

When I do mine, I fill the radiator through the cap that's directly on it as far as it will go. Then I fill the plastic reservoir a little over the full line - definitely far enough to cover the little hose that goes down into it because you don't want that sucking air in to the system. Replace both caps. Then fill the system the rest of the way through the cap near the turbo (the highest point of the cooling system) and leave that cap off. Next, I turn on the engine and let it idle (with the heat on full blast) while I watch the bubbles escape through the reservoir cap near the turbo. Think about it - air bubbles want to go to the highest point in the system. Leave that cap off and let the bubbles escape through there. Add fluid through that point as necessary and keep a clean rag close by to wipe up any coolant that escapes since the fluid level will rise and fall as the engine changes temperatures and the fluid starts circulating. Be sure to gently squeeze the rubber (or silicone) hoses going to and from the radiator to aid the air in moving out of the system. After all the tiny bubbles are completely gone (it might take several minutes and you might have to repeat the process more than once) you should be good to go. Also, occasionally monitor the temperature gauge as the car is sitting there idling and make sure it doesn't go too high. If it creeps up really high, turn the car off, let it cool, add more fluid, and repeat the whole process. I've never had that happen, but it's just an indicator that fluid isn't getting all the way through the system and you would probably need to check for leaks and make sure all your connections are tight and make sure all fluid levels are full before trying to burp the system again. Good luck!

The stock turbo is oil and water cooled :)

wrx54 02-07-2011 11:42 PM

Update (bad news):

So I tried another round of burping, as well as a flush through the engine block drain plug.
Your instructions have been helpful; I found that warming up with the cap off to watch bubbles process out was a great method to speed filling coolant to proper level.

But the problem persists.

Even after 30+ minutes of idling and heat and a very steady bubble free level under the open cap, a five mile trip puts me back out of commission.

My suspicion is that the turbo is somehow pushing air into the system since this is where the bubbling occurs and because the problem seems to be tied to driving. After a drive the overfill reservoir literally overfills (way past the F line and up to the cap), leaving the water level in the turbo reservoir tank nearly empty. I've been using a Forrester XT (turbo) to compare so I know the turbo tank stays full and there is never a bubbling noise from the turbo coolant line as there is in my car. The Forrester is also relatively insensitive to throttle blips whereas mine tends to spew large amounts out the open cap when I hit the throttle.

I don't understand what could have caused a problem at the turbo, since there was no problem before the clutch job. I don't see what I could have changed during that install. Only other factor was a long downtime as the car sat in the garage for months.


BTW, this 2002 does not have a cap on the radiator.

What coolant do I need to use as I didn't think it would be a problem to use a tap water/green coolant mix?

pzr2874 02-08-2011 05:40 AM

Shouldn't matter on the mixing, as long as it was the green shtuff before...

What do you mean by there isn't a cap on the radiator ? Missing or it's a closed radiator ?

Any smoke ?

wrx54 02-08-2011 04:16 PM

2002s have a closed radiator. I understand later models have a cap both on the radiator and on the turbo reservoir.

No smoke.

What came out before was on the very blue side of green, but I naively believed the autozone tech who told me there is only red or green. Now I've been trying to read up on coolant colors and found one article that suggested that some blue coolants are actually closer to red than green. Could this be a problem? By now my system has been pretty thoroughly flushed with green coolant.

wrx54 02-08-2011 08:24 PM

Update (good news):

So I flushed once more and switched to a universal coolant, supposedly intercompatible with anything. On recommendation of a fellow engineer, I'm running this new fluid at 100% coolant, 0% water. I was extra thorough about filling, especially regarding run time at 3000 rpm.

I also squeezed out a substantial air bubble in the bottom radiator hose leading to the thermostat. I highly recommend squeezing here in addition to squeezing the top hose which is more frequently mentioned.

Problem solved!

Thanks all for your help!

pzr2874 02-09-2011 05:42 AM

Never knew that of the 02's... interesting. Glad all came out correctly.

wagonracer 02-09-2011 07:12 PM

Just a little side note for those that think we should be running Subaru coolant only: The Subaru long life coolant was developed as a band-aid for the graphite head gasket problems that exist on pretty much every Subaru built until '07 or '08. The Subaru coolant additive was another such band-aid. Since WRX's and the other turbo subies have 3 ply steel gaskets and not the problem graphite ones, there is no reason to stick with their coolant. I've been running Dex-cool (orange) for years with much success.

man show 02-10-2011 12:06 AM

Thanks wagonracer, I didn't know that.

I use both band-aids (Subaru OEM coolant + coolant conditioner) in my 07 WRX and I've had success with that too. I flush it with distilled water several times until it drains almost clear and then I refill it with a 50-50 coolant/distilled water mix and a bottle of conditioner every 30k. I guess I'm going a little overboard again, but it brings me peace of mind.

Sethsbiz 05-06-2011 08:30 PM

When burping a system Why turn on the heater?

RcrsWetDream 05-07-2011 11:15 AM

1 Attachment(s)
To make sure the coolant is running through it as that's how the heater gets the heat, it's basically a heat exchanger with the engine coolant...

I don't know how common it is for air bubbles to get stuck in there but it couldn't hurt to run. I always do it.

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