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Old 04-27-2015, 08:23 PM   #1
SubieEngineer
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Default 07 STI Pushing Coolant Out Overflow

Got a question for you mosport drivers... So, for the last several months, my STI has been pushing coolant into the overflow reservoir and spilling it out if pushed on the track. This never happens in daily driving, and the overflow won't change. During AX, the overflow will get maybe 3/4 full, but it's all sucked back into the system after regular driving. Driving it hard at the track and it will overflow the reservoir and spill into the engine bay, and I've seen it bubbling into the reservoir after a cooldown lap. I did have to add coolant twice after the car mostly cooled off and I saw the level in the overflow was below the Min line. I'm still using the stock upper tank and radiator caps.

Now, my OEM coolant gauge and my Defi coolant gauge (sensor in the upper radiator hose) never get scorching hot when on the track. The OEM gauge hovers a few ticks above 1/3 and doesn't move, and the Defi registered ~210 during 2 sessions yesterday, towards the end. Regular driving I see the Defi register ~190 or so. My coolant is 50/50 mixed, too.

I do have a Defi oil temp gauge, and it will get hot while on track... Normal driving I see 200, (210ish if I'm constantly pushing 85-90 or so). On track, it's easy to hit 220 before the first hot lap, and 240-260 is the normal range. I usually start backing down around 260 (oil temp sensor is in the rear port on top of the engine, for reference).

Now, do you think it's my headgaskets...? I don't see any obvious oil in the coolant or vice-versa. What should be my next step to test, a compression/leakdown check...? I'm considering just draining all the coolant in the system and filling it with distilled water, then driving that a few days as a "flush," then draining the water and replacing it with a 50/50 mix. If the "flush" fixes the issue, sweet. If not, hopefully just a radiator/oil cooling upgrade will be necessary.

For reference, here's my engine/exhaust mod list:
1. TopSpeed RR.5 Shortblock
-CP Pistons (99.75)
-Manley Rods
-ACL Bearings
-08+ STI Nitraded OEM Crankshaft
-08+ STI OEM Water Pump
2. Cobb Catted Turboback
3. TopSpeed Tuned, 22.5 PSI street and 18.5 PSI race maps (all coolant issues are using the race map)
4. Tomei Equal Length Headers w/ Uppipe, GrimmSpeed Ceramic Coated and Wrapped with DEI Titanium Exhaust Wrap
5. APS 70mm CAI
6. Mishimoto Black Silicone Turbo Inlet
7. ETS TMIC
8. Walbro 255 LPH Fuel Pump (GSS 342)
9. Injector Dynamics 1000cc Injectors
10. Killer B Oil Pickup
11. Killer B Baffling/Windage Tray
12. Grimmspeed EBCS
13. Air Pump Delete w/ KS Tech Block-Off PLate
14. TopSpeed TGV Deletes
15. GrimmSpeed 3mm Phenolic Intake Manifold Spacers
16. Crawford V2 Air-Oil Separator
17. NGK 1-Step Colder Spark Plugs
18. Blouch Dominator 1.5 XT-R Turbo w/ 10cm Exhaust Housing, Hotside Ceramic Coated
19. Gimmick Motorsports AfterMAF Hose

I've seen this thread, which linked to this IWSTI thread that I'm still reading, but wanted to gather some opinions. After talking with a friend of mine, a hydrocarbon test seems to be in order, as that'll have the most accurate results.

Thoughts...?
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Old 04-27-2015, 11:39 PM   #2
newtothescene
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Most likely a blow HG. I'd get a leakdown test to be sure.
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Old 04-28-2015, 12:02 AM   #3
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Quote:
Originally Posted by newtothescene View Post
Most likely a blow HG. I'd get a leakdown test to be sure.
That's what I'm hoping it's not...! I'm going to pick up a hydrocarbon tester to use this weekend, too. Likely this one: http://www.uview.com/index.cfm?dsp=p...productid=5122
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Old 04-28-2015, 12:39 AM   #4
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Sounds like a head gasket. Probably is a head gasket. Combustion getting into the cooling system will push coolant out with ease. It also may not show up on a leakdown test. Mine didnt.
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Old 04-28-2015, 02:13 AM   #5
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Quote:
Originally Posted by bhhamblin View Post
Sounds like a head gasket. Probably is a head gasket. Combustion getting into the cooling system will push coolant out with ease. It also may not show up on a leakdown test. Mine didnt.
Yay... Using a combustion test kit, do you stick it in the radiator, the upper tank, or the overflow...?
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Old 04-28-2015, 02:44 AM   #6
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What head studs did you use? Or did I miss it
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Old 04-28-2015, 11:31 AM   #7
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It could be a head gasket but not necessarily. These cars are prone to localized boiling when they get a little hot. If you are tracking the car, you should take a few precautions to keep temps down. On my old STi I had a similar problem and after going through the cooling system and upgrading it never happened again.

-Add engine oil cooler
-Add upgraded radiator
-Replace upper coolant reservoir cap with high pressure cap
-Dilute coolant mixture or run 100% distilled water with a bottle of water wetter

It also greatly helps to remove the A/C condenser but that's not really practical if it's still a street car. Try these things and see if it resolves the issue, you may not need to replace the head gaskets.
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Old 04-28-2015, 11:40 AM   #8
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Quote:
Originally Posted by richy_21 View Post
What head studs did you use? Or did I miss it
I can't remember... My invoice doesn't specify anything specific.

Quote:
Originally Posted by boost junkie View Post
It could be a head gasket but not necessarily. These cars are prone to localized boiling when they get a little hot. If you are tracking the car, you should take a few precautions to keep temps down. On my old STi I had a similar problem and after going through the cooling system and upgrading it never happened again.

-Add engine oil cooler
-Add upgraded radiator
-Replace upper coolant reservoir cap with high pressure cap
-Dilute coolant mixture or run 100% distilled water with a bottle of water wetter

It also greatly helps to remove the A/C condenser but that's not really practical if it's still a street car. Try these things and see if it resolves the issue, you may not need to replace the head gaskets.
I'm hoping I can go this route... If the cooling system can't handle track work, that's a much simpler fix than HG replacement. The radiator and engine oil cooler have been on my list for awhile, and I'm thinking about more distilled water and less coolant (I still drive it on the street semi-regularly).

Where would I source a higher-pressure upper tank cap? OEM or aftermarket?

Last edited by SubieEngineer; 04-28-2015 at 11:46 AM.
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Old 04-28-2015, 11:53 AM   #9
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http://www.rallysportdirect.com/High...e-Radiator-Cap

I used the STi cap but as you can see, there are plenty of cheaper options.
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Old 04-28-2015, 12:07 PM   #10
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I'll make bets it's a head gasket. My car pushed coolant for a while. I tried most of the things listed above until I gave in and got the HGs replaced. Sure enough, that was it, and ever since it doesn't push coolant at all, even during 1/2 hour hard stints on track.
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Old 04-28-2015, 12:23 PM   #11
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Is there any benefit to any of the non-water or regular coolant solutions, like Mishimoto's Liquid Chill or Evans coolant?

Quote:
Originally Posted by boost junkie View Post
http://www.rallysportdirect.com/High...e-Radiator-Cap

I used the STi cap but as you can see, there are plenty of cheaper options.
Thanks for the link!

Quote:
Originally Posted by mav1c View Post
I'll make bets it's a head gasket. My car pushed coolant for a while. I tried most of the things listed above until I gave in and got the HGs replaced. Sure enough, that was it, and ever since it doesn't push coolant at all, even during 1/2 hour hard stints on track.
How did you confirm they were done before you replaced them...?
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Old 04-29-2015, 09:46 AM   #12
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Quote:
Originally Posted by SubieEngineer View Post
How did you confirm they were done before you replaced them...?
I run just water and water wetter. I never had it tested, but you could see the "coolant" wasn't clean in the overflow. That, and it started pushing more and more coolant.

Once the old head gaskets were removed, it was pretty clear to see where they were leaking.
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Old 04-29-2015, 10:47 AM   #13
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Quote:
Originally Posted by mav1c View Post
I run just water and water wetter. I never had it tested, but you could see the "coolant" wasn't clean in the overflow. That, and it started pushing more and more coolant.

Once the old head gaskets were removed, it was pretty clear to see where they were leaking.
Yeah... I'm hoping for a definite diagnosis before I go through the end-all step of having the HGs replaced. My coolant still looks like coolant, not the milky stuff, thankfully. I've ordered the tester kit and it'll be here tomorrow. Hopefully the combustion leak test will be definitive...
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Old 04-29-2015, 05:42 PM   #14
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We've seen a few head gaskets on STIs. It seems more common on race cars, maybe because long downtime periods allow moisture corrosion to form at the bottom of the cylinders. As mentioned, a leakdown test will not always give a positive result. On one recent car we worked on, the leakdown results were fine, but the head gasket was definitely leaking.



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Old 04-29-2015, 07:49 PM   #15
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Just went through the same thing with my 06 STi. It's the head gasket(s). Go ahead and get it done, and go have fun.

Mine was totally fine driving to work, or just cruising around anywhere, and would fill up the coolant overflow tank during rallyxes. Eventually got bad enough that it was BLOWING coolant out the overflow tank during every run at the last one.

For months, I thought it was the radiator cap(s), or the overflow hoses, or whatever else I could find to support my denial, because it wasn't that bad at first. But eventually it was pretty obvious it was the head gaskets.

You can replace them now, or wait until it becomes a lot worse, but you're gonna have to do it sometime.
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Old 04-29-2015, 07:59 PM   #16
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Thanks for the advice, guys! I'll update when I run the combustion leak test... I just hate having to yank the motor for something after having a rebuilt one installed a few years ago. Oh, and the $$$ it's going to cost...
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Old 05-01-2015, 01:25 AM   #17
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Another thing you need to be careful about is all the other problems you may encounter if kept too long - oil dilution resulting in spun bearings, lowered octane resulting in preignition. Just an FYI. May not happen but the chances are higher now that you have this issue. Good luck.
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Old 05-01-2015, 05:03 PM   #18
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As others said I had the same problem. Mine would only boil over on cool down laps. Otherwise it ran fine. Replaced the HG and added ARP head studs and no problems since.
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Old 05-02-2015, 01:44 AM   #19
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So the combustion leak test was inconclusive... I tried the "regular" test using the upper tank and a spill-proof funnel so the coolant had room to expand (I wound up sucking some out before then), then the "severe leak" (or whatever it's called) where I had my GF rev the engine while I used the tester. Never changed color. I'm still not convinced, though.

Quote:
Originally Posted by newtothescene View Post
Another thing you need to be careful about is all the other problems you may encounter if kept too long - oil dilution resulting in spun bearings, lowered octane resulting in preignition. Just an FYI. May not happen but the chances are higher now that you have this issue. Good luck.
You know, this would explain why my STI has been more finicky with the fuel it uses... Tends to want to throw a cylinder 4 misfire code, which started appearing more often on track (would pop up during the first laps of the first session, then stay gone if I cleared the code). Goes away on its own when I run some 100+ mixed with name-brand 93, and would randomly .

Quote:
Originally Posted by elirentz View Post
As others said I had the same problem. Mine would only boil over on cool down laps. Otherwise it ran fine. Replaced the HG and added ARP head studs and no problems since.
Exactly my problem. It seems I can run the heat at full blast all session and it may trickle out on my last lap or so (including cool down).
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Old 05-06-2015, 08:30 PM   #20
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Interested in seeing the resolution to this, the temp gauge on my 06 will stay rock solid the entire track session, the entire cool down lap, and into the infield, then when I park it and turn it off it forces out a ton of coolant. I don't run the heat on the track, and the fans are operating correctly
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Old 05-06-2015, 09:47 PM   #21
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My fault, sorry.
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Old 05-07-2015, 11:00 AM   #22
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Originally Posted by The Satch View Post
Interested in seeing the resolution to this, the temp gauge on my 06 will stay rock solid the entire track session, the entire cool down lap, and into the infield, then when I park it and turn it off it forces out a ton of coolant. I don't run the heat on the track, and the fans are operating correctly
I'm working on it...! I have some ideas, we'll see what happens in the next few weeks.
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Old 05-07-2015, 11:55 AM   #23
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I wonder what it could be. Hmmm... (scratches chin)

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Old 05-07-2015, 02:22 PM   #24
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Quote:
Originally Posted by Fred View Post
I wonder what it could be. Hmmm... (scratches chin)

I'm still hoping it's not the HGs, but I'm going to take a step by step approach, with the cheaper/simpler fixes, first.

Tomorrow I'll buy 2 new caps for the radiator and upper tank, and replace the coolant with distilled water and water wetter. I have an AX Sunday, I'll see if the overflow bottle fluid level changes, then.

Next step is to pick up an upgraded radiator (Mishimoto X-Line) and oil cooler, and install those with a stock-pressure radiator cap and higher-pressure upper tank cap (no more than 1.3 bar, since my OEM radiator cap is 1.37 bar). Maybe upgrade to silicone upper/lower hoses while I'm at it.

With that last setup, I can see what it does at the track. If it's still pushing coolant... Well, yeah, it's the HGs. Else, hopefully I'm in the clear for quite awhile!
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Old 05-08-2015, 09:27 AM   #25
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Quote:
Originally Posted by SubieEngineer View Post
I'm still hoping it's not the HGs, but I'm going to take a step by step approach, with the cheaper/simpler fixes, first.

Tomorrow I'll buy 2 new caps for the radiator and upper tank, and replace the coolant with distilled water and water wetter. I have an AX Sunday, I'll see if the overflow bottle fluid level changes, then.

Next step is to pick up an upgraded radiator (Mishimoto X-Line) and oil cooler, and install those with a stock-pressure radiator cap and higher-pressure upper tank cap (no more than 1.3 bar, since my OEM radiator cap is 1.37 bar). Maybe upgrade to silicone upper/lower hoses while I'm at it.

With that last setup, I can see what it does at the track. If it's still pushing coolant... Well, yeah, it's the HGs. Else, hopefully I'm in the clear for quite awhile!
Quite frankly, I think most of that is a waste of money, at least if viewed in terms of its usefulness in diagnosing your current problem.

I'd probably replace the radiator cap just to be sure, but if it still pushes coolant and you've pressure tested the system to make sure you have no leaks it's almost certainly the head gaskets, which you could just about fix for the money you're planning on spending on an upgraded radiator and oil cooler.

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