hello, i've just bought an Octavua vrs

Car was fine for first week but now it feels slower and I can hear a hissing sound as boost builds up

I have checked all the pipes, no holes or leak

Checked intercooler, which was fine.

Cleaned TB

No misfire, no warning lights illuminated.

I found this pipe which wasn't attached to anything, could this be the cause of the leak? Where does it go?

That's part of the Secondary Air Intake system, & should be connected to the OEM air box, but you have an aftermarket cone filter (Bad idea as sucking in hot air is a great way to lose a few horses).

If you can hear hissing you've definitely got a boost or vacuum leak.

Thanks for the replies Paul

Its definatley an air leak but i've taken off and removed every pipe I could

No holes

If my BOV was faulty, Would it still make the dump valve/turbo chatter noise? (Hmmmptisssh)

VAG 1.8T's don't like BOV's they need a recirc valve. If you actually have a recirc valve fitted it shouldn't chatter or go "Hmmmptisssh" If it does the seal has failed.

Most common pipes to split are all the small ones around the inlet manifold, & the S pipe under the inlet manifold.

I have exactly the same situation.  checked for leaks cant find any.  I also have like a flat spot at about 1500 revs . over that it seems ok although i can hear the turbo spinning up but the boost doesnt really kick in till about 3000 revs ,  annoying ..

Thanks for the replies guys

Today, i checked all the pipework again,including the ones under the inlet, by the dipstick, still no holes/leaks

This is the BOV thats fitted to my car, standard bosch one

Is there anyway to test if this is faulty?

Yes..  

 

Hold it in your hand.. with the other hand push the piston up with a screwdriver handle or similar.. while the piston is pushed up, place the thumb of the hand you are holding the valve with OVER THE VAC NIPPLE (top of valve)..  now release the screwdriver while holding thumb over nipple..

 

If the piston moves, it's leaking! 

If it don't, it's ok 

The piston should only move when you release your thumb 

Hi lucky

I removed the bov, the piston is already at the top, i didnt need to use a screwdriver etc, seems to be stuck.

Could this cause the boost leak?

Hi lucky

I removed the bov, the piston is already at the top, i didnt need to use a screwdriver etc, seems to be stuck.

Could this cause the boost leak?

That would do it.

I'll get a new dump valve tmrw,hopefully fixes the problems

Thanks for the help people

In a word yes.! 

Update

Added a forge DV and still the same problem

I've checked every pipe and cannot find a leak

Ahhhhh!!!

I'm out of ideas.

Heres a short video, of how the car sounds.

(Standard bosch BOV)

[Yt]http://youtu.be/rokiHi17UxY[/yt]

Sounds ok from what I can hear.

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Edited 12 April, 201412 yr by mluton

So today, i unplugged (electrical connector)on n75 valve, and my car feels smoother and power delivery is smoother as well.

Does this mean my n75 valve needs replacing?

N75 failure is fairly rare, but not unheard of.

Have a look at the part number letter stamped on the side. Standard N75 is p/n followed by a C or F.  A common mod is to put a J or H valve on, which give steeper boost spikes. Could be you have one of those fitted or your standard valve has a problem.