Car boosts and pulls, but dies off.

['96_Talon_TSi]

Alright so i've seen posts about stuff sounding like this a million times, but i think i have a different problem. Mods are : intake, intercooler pipe, 3" exhaust and evo3 16g @ 10psi. I never noticed this problem until i put the evo3 on. It's a used turbo, but had no shaft play and spun freely.

The car will boost fine when under load and it pulls pretty well, but when i get into higher RPMs it does off. Sometimes the car will burn coolant and blow white smoke out of the tailpipe, but not always.

Hoping to find a blown headgasket to slove the problems i performed a compression test and came up with this:

cyl1 - 162psi
cyl2 - 150psi
cyl3 - 160psi
cyl4 - 162psi

The engine wasn't at running temp when the test was performed, so i expected the numbers to be a bit low. The test doesnt bother me but cyl #2 had me concerned, so i performed a cyl leak test.

The leak test showed no leaks on cylinders 1,3,4 (no leaks in intake valves, exhaust valves, crankcase, or bubbles in coolant) but there was an exhaust leak in cylinder #2. There was no air coming out of the crankcase, throttle body, or bubbles in the coolant,however there was air coming out of cyl #4.

I'm thinking its either Cyl #2 exhaust valves arent seating correctly (carbon buildup or collapsed lifter)

However someone suggested to me there may be a hairline crack in the #2 combustion chamber that opens up when i hit boost, or that the head could be warped around cyl #2.

I'm totally stumped on this problem, any help would be awesome.

Thanks guys.

 

[T2Small]

If the coolant burning is not consistent, I would be suprised if the compression check did show a headgasket problem.

I would suspect the headgasket first, but it may not be "gone" enough for you to really notice it. Why don't you pull the head? It is very likely to be head or headgasket related, and that is the only way to know 100%. I suspect that at a certain temperature or pressure the headgasket is finally seeping coolant, but under other conditions it seals fairly well.

There really is not many other ways to get coolant into the exhaust besides the headgasket. I suppose you could have some coolant in the oil, and you are burning the "oil and coolant" mix. But that shouldn't look or smell like burning just coolant.