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Discussion Starter #1
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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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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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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Discussion Starter #8
snorky said:
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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STimo said:
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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zell_06 said:
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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Basically what I did is run the 1.3Bar STI cap on the fill tank and everything has been fine so far... I think the 1.4 Bar crucial cap on the fill tank was a bit higher than the 1.37bar one on the rad... I think the idea is u want to run the rad one a BIT higher than the one on the fill tank... so I run 1.4 (1.37) bar on the rad (stock) and 1.3bar (STI) on the fill tank... seems to be ok so far... will report back after next full track event.
 

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AnorexicSTI said:
so I run 1.4 (1.37) bar on the rad (stock) and 1.3bar (STI) on the fill tank... seems to be ok so far... will report back after next full track event.
+1 this is what i have been running for a year. with multiple track and autoxs. i don't have a coolant temp gauge (aside from stock) so i cannot comment on the cooling benefits. however my stock gauge does not ever move above the slightly below half spot that it always occupies when the engine is fully warmed. obviously the stocker isn't a very good indicator/measuring device but my point is that i have not seen an ill effects.
 

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Have you overheated? If not, then put the caps down and leave it all alone. If anything, drain some fluid and pour in a bottle of WaterWetter and distilled water....best thing you can do to shed heat.

Distilled water and WaterWetter...do it.

Be good,
TomK
 

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They say if you going to use 1.3 radiator cap, use silicone or performance hoses.
 

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ace996 said:
Have you overheated? If not, then put the caps down and leave it all alone. If anything, drain some fluid and pour in a bottle of WaterWetter and distilled water....best thing you can do to shed heat.

Distilled water and WaterWetter...do it.

Be good,
TomK
water wetter is garbage
 

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Discussion Starter #18
Okay, so I need a higher pressure at the ratiator than the one next to the intercooler?
 

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For me I would leave the fill tank cap along.
My opinion is if I put a higher pressure cap on the fill tank, that means I need more pressure to open up the cap and let the coolant run into the turbo and engine, another word means it is harder to let the coolant to get in and cool down the turbo & engine. only my 2 cents......
 

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your understanding of the cooling system is incorrect. the thermostat is what keeps fluid from circulating into the sytem. that is on the other side of the system. once the coolant reaches the thermostat's opening temperature("ideal" operating temperature), the thermostat begins to open.

the high pressure cap allows more pressure to be built up inside the system before it is dumped into the return (or reservoir in the case of the radiator cap). the higher pressure raises the boiling point of the fluid and reduces water pump cavitation.
 
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