*sigh* boost leak

[curlyks2]

Errr... title says it all really. I have a boost leak somewhere. Boosts quite happily to c. 1 bar, then above that I can just hear all the boosty goodness whistling away. Don't know yet whether it's a hole or a hose/clip shifted a little (or something else) - that looks like a job for the bank holiday weekend.

[Rusty]

D'oh. Bain of the S2 owner's existence

[istoo]

i think i have the same, either that or somewhere has put a whistling kettle under the bonnet somewhere.

[paul.m]

i think i have the same aswell. Seems to have lost performance, big flat spot around 4000rpm and whistles alot. I've ordered that pipe to replace the intercooler o-ring, and intend on replacing all the boost hoses for new silicon ones (samco, roost or similar)

[Rusty]

@ Paul, if it's stock, you will have a leak, the hoses degrade over time. Mark H mod, Samcos and new vacuum lines are the way forwards, then pressure test the whole lot to 1 bar if possible! The breather should be fully sealed as well, if possible.

[paul.m]

could you elaborate on what you mean about the breather? I am wondering if there is an issue with a breather valve somewhere because very rarely it will puff out blue smoke but i can never get it to do it on cue. It seems its completely random, sometimes after flooring it, sometimes when cruising at 50mph in 6th and sometimes just on a gentle over-run it will just puff out the smoke once, not for any length of time

[curlyks2]

Think I've found mine - see picture. The right angled rubber pipe indicated is split under the hose clamp and leaks air even under the light pressure of a couple of bungs and a bicycle pump.

Can anyone tell me (a) whether the right angle is available separately from the rest of the hose system it's connected to, and (b) appropriate part numbers? Many thanks.

[veneto rs2]

Yes the rubber angle it's available separetely
And still being supply (bought one myself few days ago)

Part No 034 133 997 J
about 9,00 euros in Italy

[Rusty]

That isn't under pressure so will not act as a 'boost leak' as it's a breather hose and so is at atmosphere at a maximum. A small breather leak will not cause too many issues but it is good practice to have it all sealed up so the car runs correctly. IME a leak on the low pressure side can cause a slight cough when coming on boost and maybe a rough idle but as before, it won't cause any boost issues. I suggest you block the breather pipe in the inlet and try again as the problem is elsewhere...

[UrS4boy]

That isn't under pressure so will not act as a 'boost leak' as it's a breather hose and so is at atmosphere at a maximum.

Sorry but I think you are wrong. Normally true but if the non-return (PCV) valve or the pressure control valve are fubar'd then you can have that crankcase vent under pressure, as shown, in this AAN-related post:

http://forums.quattroworld.com/s4s6/msgs/22506.phtml

All the hoses and valves in that system need to be in 100% working order.

[Rusty]

Aye, worth a check. All located under the IM and TB.

If the non return valve is broken then the car will run like crap as it will be leaking boost back to the low pressure side of the turbo, similar to a broken DV, it will also be pressurising the breather and block.

The order of components is slightly different on the S2 to the AAN diagram above due to the different inlet position, the PCV is before the 1 way valve on the S2 with the 1 way valve linking the head return pipe to the N80 T piece (blue plug / ~1" OD blue valve).

As before, block the breather on the inlet boot and pressure test again. If that's inconclusive then you can go a bit further.

If you want to eliminate the breather from your investigations while driving then you need to do the following.



Use some 8mm fuel hose, a bolt and 2 clamps to block the pipe that goes into the IM under the TB area, block the pipe that used to go from the N80 into the IM, again with an 8mm bolt and block the inlet hose too using a 19mm bung. The pipe that used to go into the inlet boot pipe can be covered with a breathable gauze or filter to prevent oil going over the engine. It's a short test so should be OK but you've been warned!

For a longer term test you can either run a pipe from the N80 to the inner wing or disconnect the breather in the boot and again using some 8mm hose, route it through the rear breather flaps in the boot - you don't want fumes in the engine bay or car!

This will eliminate the breather system from your investigations, when it's all running properly you can re-connect it (hopefully after a thorough inspection and replacing any damaged parts) and see where you get to.

[paul.m]

ok cheers guys. The cars used about 2.5 litres in 2 weeks now. Think it may be the turbo. The spindle seems to have about 25 thou play up and down , and about 2 thou end float.

[curlyks2]

Pipe replaced (see picture for the old one, including big split), system checked, boost and smile restored.

[istoo]

Pipe replaced (see picture for the old one, including big split), system checked, boost and smile restored.

Looks like a tiny elbow, and appears to be under the clip that holds it, means i have a lot of checking to do!

[curlyks2]

Looks like a tiny elbow, and appears to be under the clip that holds it, means i have a lot of checking to do!

Not the biggest of parts, true. Happily though it isn't/wasn't a difficult one to get to - the first picture in the thread shows where it is, and to get to it it's two hose clips and three bolts to remove the intake pipe, and then you've got clear access.