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Dual STi radiator cap?
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Old 06-15-07, 09:07 PM   #1
Gouki
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Question Dual STi radiator cap?

After doing some research I've read that the cap next to the intercooler is the one to replace with the STi high pressure cap. I've come in possesion with two of these, so would it be beneficial/hurtful/ect to run two caps, one next to the intercooler and one on the radiator itself?
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Old 06-15-07, 10:18 PM   #2
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Default Re: Dual STi radiator cap?

I'm pretty sure that is what you are supposed to do. Make sure your lines are in good condition and you might consider upgrading to silicon hoses too.
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Old 06-15-07, 11:36 PM   #3
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Default Re: Dual STi radiator cap?

Heh heh, that's what I was thinking...
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Old 06-16-07, 01:22 AM   #4
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Default Re: Dual STi radiator cap?

No that is wrong, you only want to replace one (i believe the radiator) with the sti high pressure cap, it has to do with draining or something and if you run both caps the pressure will be the same in both and you wont get any drainage, causing the car to overheat or something.. I've actually read that some shops recommend that you dont use those caps and that the stock ones are fine.. So if you have two caps and wanna run them, IMO i would just run one and sell the other just to be safe..
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Old 06-16-07, 09:46 AM   #5
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Default Re: Dual STi radiator cap?

The cap on the upper tank says 108kPa on it.
The cap on the radiator says 137kPa. So that means the radiator cap has a higher pressure relief on it. Plus it's vented to the coolant overflow tank. The upper tank has all those lines on it for cooling the turbo on shutdown. So I think that maybe that cap goes on the radiator.
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Old 06-16-07, 09:52 AM   #6
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Default Re: Dual STi radiator cap?

I put the sti cap on my radiator and it blew that hose off. I slapped it on to the tank near the turbo and no problems.
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Old 06-16-07, 11:32 AM   #7
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Default Re: Dual STi radiator cap?

the upper tank is where the aftermarket 1.3 bar cap goes. 137kpa=1.37 bar. replacing the radiator cap is redundant.
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Old 06-16-07, 12:23 PM   #8
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Default Re: Dual STi radiator cap?

Quote:
Originally Posted by snorky
the upper tank is where the aftermarket 1.3 bar cap goes. 137kpa=1.37 bar. replacing the radiator cap is redundant.
Thanks for all of your responses.

Snorky:

So it'd be fine to replace the radiator cap with the STi cap, it just won't change anything?
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Old 06-16-07, 12:29 PM   #9
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Default Re: Dual STi radiator cap?

Quote:
Originally Posted by STimo
No that is wrong, you only want to replace one (i believe the radiator) with the sti high pressure cap, it has to do with draining or something and if you run both caps the pressure will be the same in both and you wont get any drainage, causing the car to overheat or something.. I've actually read that some shops recommend that you dont use those caps and that the stock ones are fine.. So if you have two caps and wanna run them, IMO i would just run one and sell the other just to be safe..
I ran a 1.4bar Crucial Racing cap on the fill tank on the track... had some overheating problems... what would happen is the system would pressurize, not be able to "bleed off" and fill my coolant bottle to the top... and then for whatever reason, it would not get sucked back in when the pressure relieved itself... on the street this setup was fine.
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Old 06-16-07, 12:31 PM   #10
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Default Re: Dual STi radiator cap?

Quote:
Originally Posted by zell_06
I put the sti cap on my radiator and it blew that hose off. I slapped it on to the tank near the turbo and no problems.
This doesn't make sense.. the one on the rad is 1.4 bar... the one on the fill tank is 1.1 bar.. so if u put the 1.3 bar Sti cap on the rad, it would actually bleed off BEFORE the stock 1.4 bar one... if any hoses are blowing off, they need to be tightened down.
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