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Thread: Boost/Vac Leak TB shaft issues

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2015-11-11 21:08:48
Boost/Vac Leak TB shaft issues
I have searched the forum and seems like people with similar issues found a way to fix them but did not report back as to how. I have a low port DE with an OEM t25 kit, upon testing it for leaks I came across the shaft of the TB leaking on both sides (cable side, TPS side). I went ahead replaced it with a spare TB out of a spare low port but ended up leaking as well. While pressure testing the system comes up to 20psi +/- 2psi and will not go past that. It takes about 17seconds to lose all the pressure out of the system. I am using a 12v. Electric air pump and it seems the air leaking past the TB is greater than what the pump can supply at 20psi; so it manages to settle around that pressure. I suspect that I ruined the first TB by using compressed air from the shop at work and bumping the pressure up to about 70 psi. I don't intend to run 70 psi, but at the time of testing the higher pressure made it easier to hear and find the leaks. Yeah I Fudged up.

So I now have two options,

A. Replace the TB with a different unit until I find one that doesn't leak.
B. Find a repair kit or better yet buy a set of aftermarket seals for the existing TB.

I searched on the forum and found this TB Boost Leak?

Any one else have some experience with this issue?

I'm sure someone will chime in and tell me to do a boost leak test or search the forum....... Well I already did, several times and spent hours on both Google and on this forum. Information on boost leaks is all over the place and most are car/engine specific and it’s usually some guy who doesn't know squat trying to give advice.

I have the cap at the turbo inlet, I have tested hot side only, hot and cold capped off before the TB, and just recently I have tested with the cold side connected to the TB. I have read that turning the #1 piston to TDC is the correct way to test, but have not done that just yet.

I have typical boost leak symptoms, pig rich at idle, part throttle and tends to lean out at WOT. The IC pipes alone will hold pressure although I do think the BOV is not holding pressure past 25psi. Even with the adjustment set to full hard.
So I ended up changing the system to blow through as opposed to draw through. At initial start up the car will idle @ 14.7 afr then slowly go to 10 afr and the rich condition.
Set up is,
Low Port DE / Avenir T25 kit / 370cc inj / calum RT / ebay 2.5 IC piping kit / knock off greddy type s bov / E60 maf (currently blow through)

2015-11-12 12:12:57
Bump. Any one with ideas?
2015-11-12 13:33:33
I don't know of a TB repair kit but as for the BOV, teflon tape on the adjustment screw fixed my leak.
2015-11-12 13:56:29
It actually doesn't leak past the adjustment screw, it did come with a small Viton ring that squeezes in between the nut and the housing. The BOV has been one headache after another, first the flange was warped so I had to fly cut it back to tolerance. Then the cheap gasket went out, got some Permatex and fixed that issue. Then the vacuum fitting on the top snapped off (during our drive out to Lockhart for BBQ), replaced it. Last but not least fighting the compressor surge vs. spring tension.
Too tight = Bad bov flutter/compressor surge.
Too loose = open @ idle / leak @ full boost.

I'm done with this bov, I actually bit the bullet and bought a 3rd gen SSQV along with the recirculation fitting. It is supposed to stay closed @ idle, the more boost the stronger seal, and best part works at all boost/load levels! No Adjustment !

Patiently waiting on the adapter so I can bolt this bad boy in.
2015-11-12 14:33:09
Sounds like ur typical Chinese trash parts
2015-11-12 21:19:17
I had issues with the greddy knockoffs, switched to a hks knockoff an problems went away.. running the same bov on a friend's car too.
2015-11-13 12:22:35
Originally Posted by lynchfourtwenty
I had issues with the greddy knockoffs, switched to a hks knockoff an problems went away.. running the same bov on a friend's car too.
Does it really stay closed at idle? I read the HKS only opens when a pressure difference exists in the internal chambers, but at idle vacuum is present and the underside of the valve never really sees vacuum...? Have you ever tested your TB? Maybe its so common that I may not have to worry about it lol.
2015-11-14 17:48:12
No never tested my TB. I run draw thru with recirculation as God intended lol.

I've also never tested my bov or my friends.. when we first boosted his car we used an older style his knock off that was "adjustable" but it acted a lot like the greddy one I had.. now that he has a newer style like mine it seems to work better.. no flutter at low boost shifts and it's quieter on higher boost shifts.. tho our 2 bovs are identical and intake setups and recirculation is basically the same they each sound different, mine is overall more quiet of the 2
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