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Old 04-07-2008, 12:08 AM   #1
gakusya
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Default Cooling system problem

Coolant is not returning to the engine from reservoir after cooling down. For city driving, it can still recirculate but not highway driving. After driving on the highway, I can see a lot of bubbling in reservoir tank. I can see some particles like carbon dust and color change of coolant. Is there any way, I can find out which bank is injecting exhaust gas in the cooling system?
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Old 04-07-2008, 01:39 AM   #2
fastnoypi
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if you are seeing an extraordinary amount of steam in your exhaust , you might be able to tell by just dropping your exhaust manifold and seeing which side has some coolant residue in the port.
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Old 04-15-2008, 03:35 PM   #3
gakusya
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I checked coolant and compression but everything was normal. Coolant test indicating that air bubbles are not from exhaust (fresh air). Is there any other possibility where the air can go into cooling system?

Thanks,
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Old 04-15-2008, 10:24 PM   #4
4cylFI
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Default Just boiling?

I may have missed something, but are you sure that the coolant isn't simplying boiling in the overflow tank? Since the radiator operates under pressure, the coolant can be over its boiling point when not under pressure (ie you either open the cap or it gets pushed to the overflow reservoir).

That said, my forester isn't sucking everything back from the reservoir as it cools either. I plan to do a close inspection on the tube from the radiator to the overflow to see if it has any pinholes, cracks, etc.. which may reduce the vacuum that sucks the liquid back in.

Good luck.
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Old 04-16-2008, 03:31 PM   #5
gakusya
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If it is just boiling, I don't care at all. The main problem is that overflowed coolant in reservoir tank is not going back to the engine and getting a lot of air in the cooling system.

If there are bubbles in reservoir tank, I do need to idle the engine for at least 10 minutes to stop bubbling. Otherwise, coolant won't return to the engine.
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Old 04-16-2008, 05:37 PM   #6
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radiator cap
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Old 04-16-2008, 06:24 PM   #7
gakusya
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Quote:
Originally Posted by nv-wrx View Post
radiator cap
Thanks for your reply but I already changed both caps twice.
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Old 01-14-2009, 03:24 AM   #8
gakusya
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Default Finally, I found a solution!

The problem was caused by the coolant (Prestone).
I switched to Honda coolant 2 months ago, which solved the problem. (I connected to tap water and run it for an hour to rinse the system before switching the coolant.) Basically, Honda coolant is also silicate free as Subaru. (I believe the most of Japanese brands are ok to use in Subaru, if you flush the system completely before filling in.)
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Old 01-14-2009, 10:45 AM   #9
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Make sure the ear'd rad. cap is on the high point above the turbo, the round cap goes on the radiator. The ear'd cap allows the vacuum back to the engine.

Seems strange that the coolant itself fixed the problem, did you find alot of build up w/ the prestone?
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Old 01-14-2009, 02:31 PM   #10
gakusya
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Quote:
Originally Posted by strohausii View Post
Make sure the ear'd rad. cap is on the high point above the turbo, the round cap goes on the radiator. The ear'd cap allows the vacuum back to the engine.

Seems strange that the coolant itself fixed the problem, did you find alot of build up w/ the prestone?
I know about caps because I spend a lot of time with this issue. (6 coolant flushes in the last 6 months.)

I could find many black precipitates in the reservoir when Prestone was in. Since I switched to Honda coolant, the coolant level is always within the normal range.
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Old 01-14-2009, 03:12 PM   #11
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in the early WRX's we got the black flecks in our coolant, but that was due to the bottom inside of the resevoiur plate peeling paint (under where the top cap goes).
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Old 01-14-2009, 04:43 PM   #12
gakusya
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These black things were really sticky (at the lower temperature), so everywhere inside of the reservoir. Only if there is no exhaust gas contamination (this is very simple test), the coolant switch may solve the problem.
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Old 03-02-2009, 05:23 AM   #13
letsteyr
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hi gakusya, i think i got the same problem as you got.

A WRX STI 2006 2.5L + atp3071 turbo

Coolant overflows when i drive hard (i think it's more after driving hard)
No overheat, No consumption (oil or coolant), No milk, No smoke
A few little black things (2 or 3 in the bootle)
Tryed with a 1.3b upper cap => still overflow
changed my radiator with a koyo => a little less oveflow
changed the termostat with a crucial => still overflow

Coolant has difficulty to go back into the radiator except by very low temperature.
I did the carbon test (blue/yellow test) => No carbon, fresh air.
My compressions are balanced and ok.
My sparks are ok.

My coolant water is a common elf coolant water.

Can you give details about the coolant you put (brand, specs...). Thanks
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Old 03-02-2009, 01:38 PM   #14
gakusya
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Quote:
Originally Posted by letsteyr View Post
hi gakusya, i think i got the same problem as you got.

A WRX STI 2006 2.5L + atp3071 turbo

Coolant overflows when i drive hard (i think it's more after driving hard)
No overheat, No consumption (oil or coolant), No milk, No smoke
A few little black things (2 or 3 in the bootle)
Tryed with a 1.3b upper cap => still overflow
changed my radiator with a koyo => a little less oveflow
changed the termostat with a crucial => still overflow

Coolant has difficulty to go back into the radiator except by very low temperature.
I did the carbon test (blue/yellow test) => No carbon, fresh air.
My compressions are balanced and ok.
My sparks are ok.

My coolant water is a common elf coolant water.

Can you give details about the coolant you put (brand, specs...). Thanks
It is genuine Honda coolant (I believe there is only one kind of coolant from Honda.). Plus, I added Subaru coolant conditioner. (So far, I didn't see any harmful precipitate or chemical reaction with Honda coolant.) Since I switched with Honda coolant, I have no longer have overflow problem.
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Old 03-02-2009, 11:49 PM   #15
letsteyr
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ok. You can't explain why? No idea? Where that fresh air is coming from?
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Old 02-11-2011, 09:00 PM   #16
pekoso1
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Quote:
Originally Posted by letsteyr View Post
hi gakusya, i think i got the same problem as you got.

A WRX STI 2006 2.5L + atp3071 turbo

Coolant overflows when i drive hard (i think it's more after driving hard)
No overheat, No consumption (oil or coolant), No milk, No smoke
A few little black things (2 or 3 in the bootle)
Tryed with a 1.3b upper cap => still overflow
changed my radiator with a koyo => a little less oveflow
changed the termostat with a crucial => still overflow

Coolant has difficulty to go back into the radiator except by very low temperature.
I did the carbon test (blue/yellow test) => No carbon, fresh air.
My compressions are balanced and ok.
My sparks are ok.

My coolant water is a common elf coolant water.

Can you give details about the coolant you put (brand, specs...). Thanks
I go this problem I just installed a new Mishimoto rad and caps and when I pushed the car hard the coolant overflows and bubbles come out.... But I also have a smaller coolant reservoir due to turbo xs fmic.... I don't know if thats a factor in this issue...
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