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Massive Coolant Leak on 2007 STi

1.3K views 12 replies 4 participants last post by  jedon  
#1 ·
I noticed my temp gauge getting hot so I pulled over and checked the oil which was fine, and the coolant overflow, which was empty. There was a gas station nearby so I got water and filled the overflow up, the temps went down. After a few miles the temps went up again so I pulled over and the tank was low so I added more, I figured it was getting the coolant into the system. Another few miles and same thing, topped off the tank and this time it was fine for another dozen miles to get home. Next day I go to leave and after a mile temp goes up, overflow tank level is fine, return home. I read up on it and the internet says to burp the system. Okay cool, I start to do that and it takes almost a gallon of distilled water, then I notice there is coolant dripping/pouring out underneath the car. I take the undercarriage cover off but I can't really see where it's coming from. I took the intercooler off to see what I could see, no revelations there. I added water gain and watched more closely as it leaked and it looks like from the engine? I see some mention of blown head gasket but can that much coolant loss be from the head gasket? Engine seems to run fine.
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Any help greatly appreciated!
-Jedon
 
Discussion starter · #4 ·
Thanks TC Skates and Jay11STI, I did take off the intercooler and look around and added more coolant while watching but wasn't able to see where it's coming from. There was a place that was wet and had some leaves and stuff in it, a depression in the block with a sensor, knock sensor maybe? I cleaned it up and kept an eye on it but more did not accumulate.
Do I need to take off the intake manifold to get to more coolant lines?
 
Discussion starter · #8 ·
TC Skates, ouch, I hope not, the engine already blew at 44K and I have another 44K on this one.

Thanks Jay11STI, I'll get a pressure test kit.

Thanks slammedsix!

Not too many places for coolant to be leaking on top of the engine like in your picture. You have the coolant crossover pipe has 2 o-rings that like to leak but not to that level. The coolant lines that run to and from the throttle body are pretty notorious for leaking. As mention before your best bet is to pressure test the system with a tester. Sometimes a clamp or hose will not leak just sitting but add maybe 5 psi and it start spewing everywhere. System should be tested to 20psi.

Also when pressure testing the system do it with a cold engine for safety
 
Discussion starter · #10 ·
Okay, we got the intake manifold off ( okay mostly not me... ).
My friend tried pressure testing it and it held pretty good, maybe it only leaks when hot?
There is a very wet spot on the drivers side under the manifold, perhaps it's the water crossover pipe gasket?
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Discussion starter · #12 ·
Its hard to tell but it could be the crossover pipe. I would say clean it up real good and try pressure testing again to see what gets wet and starts to leak.
Is it possible to pressure test without putting it all back together ie the intake manifold? Not exactly a trivial task... Thanks!
 
Discussion starter · #13 ·
We replaced the o-rings in the crossover pipe and put it back together, so far so good but I need a longer drive test, I pushed it pretty hard for 15 minutes or so and temps were solid and no more leaking.