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Old 11-08-2007, 06:38 AM   #1
xt2004
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Default STI MY06 overheating

I have a 2006 STI 2.5 litre, I take it to the race track, not a real race but club sprints against time, which is one warm up lap three timed laps and one cool down lap. The engine is stock standard.
The problem I have is that after I come back from the track the overflow bottle is over flowing and coolant is all over the engine that is on a 21º C day. I have been told by Subaru STI that this is normal and I should not worry about it. Now on a 31º C day the temperature rises on the temperature gauge into the middle of the third section of the gauge and much more coolant is lost, after the engine cooled down the overflow bottle is empty. I have been told this is normal, but they could fix it by fitting a STI radiator cap at a cost of $60. I now also happen in city traffic on a cool 15º C day.
I just can’t believe that Subaru would have designed and STI engine like that. The question I have is do you guys in the US have the same problem; they have the problem in Germany and have to replace cylinder head gaskets.

Cheers
Albert
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Old 11-08-2007, 10:43 AM   #2
OKR S06
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Hey Albert,

When I was reading your post I started to think if your coolant is getting that hot, a new radiator cap is not going to fix it. Your Subaru dealer telling you that its just a radiator cap is lying to you. Your car is having other problems and needs to be repaired. Your problem definitely sounds like a head gasket. Try checking your oil and see if it looks like chocolate milk.....that is a very good indication you have a blown head gasket. It could also be a water pump or thermostat. But, if I were you, I would take it in to Subaru and demand they fix this problem. I don't know of anyone here in the states having this problem. But, then again someone here might have posted about the same problem and I never have seen the post. Also, do you have any mods done to your motor?

Here is a good post I found from another guy that seems to have the same problem as you. Take a look at it.

http://forums.nasioc.com/forums/show...ht=Overheating

Last edited by OKR S06; 11-08-2007 at 10:54 AM.
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Old 11-08-2007, 03:27 PM   #3
Got Boost?
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also, be careful installing stronger, new radiator caps with the factory radiator. The factory radiator is not strong enough and will fail (start leaking) at the top/bottom tank seams.
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Old 11-08-2007, 03:42 PM   #4
android148
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yea i blew my seals out when i put a sti rad cap on my car. It the rubber seals cant take the higher pressure in the stock rad
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Old 11-08-2007, 04:37 PM   #5
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It's either:

1) Radiator cap, cause it will pump coolant into the resevoir like that if it has gone bad.
or
2) Headgaskets with an internal leak, cause the exhaust gasses will pump the coolant out of the engine into the resevoir in the same fashion.

Since they tried to replace the radiator cap, and it didn't work, its probably the headgaskets.
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Old 11-09-2007, 04:15 AM   #6
xt2004
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I can confirm they have replaced the radiator cap and the car is stock. It is going in on Monday 12th to have the rear diff replaced and have they going take out the radiator, so they say. I have done some research and found that they have this problem in Germany and in some cases had to replace pistons as well. Strangely when on of the STI owner send a letter to Subaru in Germany expressing his concern about the problem other STI owners have he basically got told they done have this problem. It will be interesting what reception I will get on Monday.

Many thanks have good weekend
Albert
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Old 11-09-2007, 02:25 PM   #7
supradupraTT
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my 04 sti used to do the same thing, it only did it once while I raced it a couple times in a row. Is your cooling fans engaging?
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Old 11-10-2007, 11:34 AM   #8
RexyGirl
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Sounds like a stupid question (but I have seen dumber things happen).....

Where does the coolant read on the bottle when the car is cold and when it is hot (not after racing it)???
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Old 11-11-2007, 01:21 AM   #9
cyrexpl
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This sounds like a headgasket issue for sure.
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Old 06-14-2008, 05:10 AM   #10
xt2004
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Well it is been a while. Just a quick report back, they changes the radiator caps to 1.3bar STI caps. This has stopped the overflow of the overflow bottle in normal driving conditions. I had no opportunity to take the car on a racetrack until just recently. The car overheated in a mayor way, it overheats once I am doing my cool down lap, not during racing. This is same symptoms happens in Germany when they are drive 200km/h on the autobahns and once slowing down their cars overheat. My car is booked in on the 17th to have the overheating “fixed”, being the first in Australia. My worries are that there seems to be no fix according to German Subaru forums, some car had have been “fixed twice”
As guys would have larger number of 2.5l STI’s than Germany and Australia, what have been the results?
Cheers
Albert
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Old 06-14-2008, 12:37 PM   #11
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head gasket... get a high pressure one. if its actually from just a lack of cooling capacity, then get an aftermarket radiator and some lightweight aftermarket cooling fans and a 160 degree thermostat... not more than 500 dollars together
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Old 06-14-2008, 08:26 PM   #12
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Quote:
Originally Posted by RexyGirl View Post
Sounds like a stupid question (but I have seen dumber things happen).....

Where does the coolant read on the bottle when the car is cold and when it is hot (not after racing it)???
+1.

I one where a guy that filled his entire overflow up with coolant when the engine was cold.
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Old 06-14-2008, 08:46 PM   #13
elirentz
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Quote:
Originally Posted by Kostamojen View Post
It's either:

1) Radiator cap, cause it will pump coolant into the resevoir like that if it has gone bad.
or
2) Headgaskets with an internal leak, cause the exhaust gasses will pump the coolant out of the engine into the resevoir in the same fashion.

Since they tried to replace the radiator cap, and it didn't work, its probably the headgaskets.
Yep! I had the same problem with my 05. Ended up being a head gasket.
Read this thread:
Iwsti Headgasket thread

When they replace the radiator caps did they replace the lower one with the pink sti one? If they did you need to have the round stock one there it is actually rated for more pressure than the pink one read the labels on both. With the way the pressures in the stock system work the lower cap needs to be rated for a higher pressure than the one on the upper reservoir.
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Old 06-15-2008, 02:14 AM   #14
xt2004
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Quote:
Originally Posted by elirentz View Post
Yep! I had the same problem with my 05. Ended up being a head gasket.
Read this thread:
Iwsti Headgasket thread

When they replace the radiator caps did they replace the lower one with the pink sti one? If they did you need to have the round stock one there it is actually rated for more pressure than the pink one read the labels on both. With the way the pressures in the stock system work the lower cap needs to be rated for a higher pressure than the one on the upper reservoir.
Well they did replace upper and lower cap with the pink STI cap.

What I would like to know is the cause of the problem.
1) are the head gaskets just plain faulty
2) if the failure of the head gasket is only a symptom of the problem, then what is the root problem?
3) faulty Waterpump
4) faulty radiator
5) or just plain bad design

I somehow it would be hard to believe that the problem is design related and in particular to the 2.5L STI, even that is were the problem is mostly manifested. We have in our club 2L STI with more than 200KW @ the wheels with standard cooling systems and no over heating problems. I uses to have 02 STI with 180KW @ the wheels and used to race in 43 Degress C with out any temerature changes on the gauge or any coolant being spilt. Now a standard 2.5LSTI with the same cooling system got an over heating problem you would think there is a faulty part. Why haven't we seen 2.5L WRX's with 180KW @ the wheel with the same problem?
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Old 06-15-2008, 12:45 PM   #15
elirentz
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I think part of it is the water pump impeller design. Here's a pic of the upgraded one I used on my new motor



The guy that helped me build the motor said that Subaru has changed the design from something similar to the one on the right to the one on the left. Its obvious to me that the older design is better.

Crawford has some good posts in that iwsti thread where they talk about they're experiences with cooling system and head gaskets in subaru's.
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Old 06-17-2008, 08:38 AM   #16
xt2004
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Quote:
Originally Posted by elirentz View Post
I think part of it is the water pump impeller design. Here's a pic of the upgraded one I used on my new motor



The guy that helped me build the motor said that Subaru has changed the design from something similar to the one on the right to the one on the left. Its obvious to me that the older design is better.

Crawford has some good posts in that iwsti thread where they talk about they're experiences with cooling system and head gaskets in subaru's.
It looks cheap, well I dropped the car of this morning, there was a long list on the worksheet of parts the going to replace.
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Old 07-10-2008, 09:52 PM   #17
subaru07
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i have a 07 2.5i and im having an overheating problem when ever i go past 100mph. im not sure if thats normal if ur going that fast but when i pulled over the tank was overflowing and the top radiator hose was sucked flat. im not sure but i think it might be the thermostat or there might be a restriction in the system.
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