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Old 05-16-2018, 07:03 AM   #1
Javiisst
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Member#: 394341
Join Date: Jun 2014
Default Subaru STI 2005, high pressure in cooling system

Hello,
I'm quite new to posting questions on this forum and I'm trying to find answers that I could not find myself.

I will use the forum more and more in the future for, among other things, my project/build I have done on my car but for now, my wondering ...

I have experienced now that the engine starts boiling / getting hot after a little dragrace on the weekend.
After a little troubleshooting and investigation, it seems when I load / launch, then it spills out glycol from the reservoir tank.
Read a bit here and there, they says the headgasket is the problem.
I bought a "block test" and the result was showing nothing at all, pictures below.

before test


after test



The car has some modefications as:
injectores
turbo
FMIC and so on but the engine itself is original EJ207 unopened. approximately 440bhp.

Now I wonder from them the experts here, what it might may be...?

Thank you for all the help and answers
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Old 05-16-2018, 08:34 AM   #2
Charlie-III
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Member#: 30669
Join Date: Dec 2002
Chapter/Region: Tri-State
Location: USA, North NJ, 07456
Vehicle:
1998 Legacy 2.5GT
Silver Sleeper BK, 5MT

Default

If you're pushing coolant out the overflow tank, then either you have air bubbles or a HG leak.
This is assuming the temp gauge is not running hot.
Air in the system can also make the interior heater run cold.

Do you keep an eye on the overflow tank? If you let is run low, that is a way to get air into the system as it cools off and sucks air in.
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Old 05-16-2018, 01:24 PM   #3
Javiisst
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The air inside the car is warm and the temp gauge is showing normal.
I have been driving normaly and filling up the expansion tank and now its all good for several days, but when i drive hard and boosting,launching then its coming out from the reservior tank and doing so several times (dragrace 10 times or so) then the temp gauge is going up = missing coolant, and i see coolant coming out under the car from the reservior when launching...

If it is/was leak from HG, shouldnt that test show something?
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Old 05-16-2018, 05:02 PM   #4
Charlie-III
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1998 Legacy 2.5GT
Silver Sleeper BK, 5MT

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Normally, yes a hydrocarbon test should show a fail if it was HG's.
It could also be a tiny leak right now that only shows with higher boost, thus higher combustion pressure.
I would burp it and keep an eye on the overflow tank. A failing HG will only get worse, not better.
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Old 05-16-2018, 09:06 PM   #5
Javiisst
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Okay I understand now what your saying and here are some new updates
I drove back home from work with cooling full in the system and drove a bit hard just for testing, when I was home then this is how the overflow tank looked like

And it was burping and coolant was coming out, engine off.

And i heard burping/air coming and going noise and it come from the turbo...

Now what is that and why is that happening?

I was thinking about the turbo before and the radiator, expansion tank cap.... Will replace them soon. But the noise from the turbo area ?
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Old 05-16-2018, 10:42 PM   #6
Charlie-III
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Location: USA, North NJ, 07456
Vehicle:
1998 Legacy 2.5GT
Silver Sleeper BK, 5MT

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I am guessing here, but it's an educated guess with science.
The turbo cooling passage is rather hot. Pressurized liquid has a higher boiling point. You have the system open, thus lower pressure and you are hearing it boil.

Now, maybe you have some other issue like low cooling flow through the turbo which is boiling the coolant even when the system is sealed. This can lead to pushing coolant just like an overheat......well.....it IS an overheat if this is happening.
Maybe check coolant flow into and out of the turbo?

As I said, I am more of a NA guy and there are plenty of others here with a lot more background in FI. But some of this is common regardless.
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Old 05-17-2018, 04:32 PM   #7
Javiisst
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okay i understand what you are saying but the turbo is a GTX3076R bolt-on so there is no modification needed with the flowing pipes and it is flowing, the sound i was talking about is when the car is off and then cooling is not running around and like you said the turbo is rather hot so maybe thats why its boiling ?

and one more thing to ad, or 2, the expansion tank is from a Subaru with the aluminium tank and the one on the car was the plastic one before but it broke... shouldnt mater?
and the other thing is that im going to change the radiator and expansion cap... see of this has anything to do with it... hard to belive it does but i want to try everything before taking the big step and taking out the engine...

someone should know this issue from experience...
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Old 05-24-2018, 09:13 AM   #8
Javiisst
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no new advices ?
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