Hi all,

Im a first time poster here and a relatively new owner.

I bought a lovely mildly modded 996 turbo in summer and have slowly been doing little bits and pieces on it.

Following a boost leak check, (20psi pumped in through the turbo cold side outlet) I discovered a large leak from a plastic valve that sits on top of the throttle body/intermediate pipe.




This is not a picture of my engine just one that clearly shows the suspect part!

I've had a google about and not much has shown up. Am I the only person who's seen it leak there? I can't be that special !

It doesn't appear the valve itself can be replaced and that it comes complete with the 'intermediate pipe' part number 99611021571. What does the valve do? Is it some sort of re-breather?

Any advice would be greatly appreciated.

 

I don't know ( sorry )which valve that pic is pointing to? and don't recognize that as anything I have ever replaced but - as another potential and likely source of minor vac leaks - is the #16 check valve. which sits very inconveniently just behind/above the plenum. the infamous #16 check valve that often develops a hairline crack resulting in just enough of a leak that if you are not aware of it. can drive you nuts when attempting to chase down minor leaks

*usually* you can detect a bit of leakage and air escaping but this must be under pressure e.g. the 20psi boost leak test. so you may need eyes and ears on that area while pressure testing

all I got. good luck w/ it.

 

That looks like the top peice to the intake plenum, I don't think that is serviceable. There is a check valve built into the top piece, on the passengerr side connection. Why are the all the hoses disconnected? Where exactly was the leak? There are 3 connectors on the top of the plenum, are you sure it wasn't one of those 3 connections, between the plastic and hose? Replacing the plenum can be done with the engine in the car, it's a bit of pain, but doable, I've done it.. I would make sure you know for sure before going down that path, which would be unusual, not sure I've heard of many issues with plenum failure, certainly loose hose clamps and the like. The check valve on the drivers side coming off that plenum is a common failure.

 

the OP says that pic is not of his car but merely representative of the location of the *mystery* leak.

the OEM plenum while made of plastic, is not prone to leaks, agreed. again, the 16 valve atop the plenum is likely the source of a vac leak. particularly if never swapped before. it's a very thin valve and hardly robust. hence its propensity for cracking/leaks.

agree also on the plenum being a b***h to remove and re-install. i replaced my OEM years ago with an IPD.

hint: drop the motor at the mounts a bit to maximize any/all possible "clearance" to remove/replace the plenum - and prepare to wrangle/wrestle with it

OP - check your check valve lol. i bet that's "it".

 

What is the PN for this #16 valve?

EDIT: Ok found it, 99611013570. Lowering my engine to replace the oil pressure sender so going to replace this valve at same time.

Example Diagram

 

#16 in the pic a common failure, #9 has been known to fail also.

 

Thanks, I replaced the plenum with a new oem one.

Boost leaks gone or at least vastly reduced!

Now I've noticed and exhaust leak on the turbo to header gasket area!!!