Possible cure for the annoying S3 over revving when changing gear


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Oct 30, 2007
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First a quick background.

Had the car for over 2 years, around about 18months ago my car had a new clutch slave cylinder fitted and since then i noticed the annoying over revving when changing gear. not so bad back then but a year later it started getting really bad. change at about 4k rpm and it would shoot straight up to 6krpm.

Car - Audi S3 2001 facelift
Jabba custom map before i bought the car
not alot else done to it.

So i replaced the clutch switch (the one on it was broken anyway. - didnt cure the over revving
Replaced a N75 valve from another S3 which didnt have the problem - didnt cure it
removed and cleaned TB then re-aligned - didnt cure it
replaced the DV with a forge one. - didnt cure it

But yesterday, i was checking the car over, checked the brake fluid res, rear left under the bonnet as if you are standing in front of the car. Noticed a rubber pipe directly above it which runs alongside my charge pipe had split, well gone brittle and cracked where it connects to a 90 degree bend. At the time all the garages had closed and i needed a quick fix to get me where i was going. so i used duct tape, taped the crack and the connecter so nothing leaked, plus a cable tie to make sure. - well this seems to of cured the over revving while changing gears. drove for around 350miles the past 2 days and its been great, it still does it very slightly but heared that remapped S3s so it slightly anyway to keep the turbo spinning.

so anyone who has this annoying issue check your rubber pipes around the brake fluid res and see if you have any split.
the only one it could be would be the servo hose, the other pipes would be hydraulic related

definately get the hose changed.

it says a lot about the places youve been taking your car to tbh
not sure its the servo pipe, it runs down behind the engine towards the turbo then 90 degree bend and follows the charge pipe down the front of the engine.

what do you mean about the places ive been taking my car? it has dont 150k miles so its probably the age.

ye getting a replacement today
Yeah its the servo pipe, Mine original and in perfect condition. When you rev your engine does air blow out of the crack, because if it does that means the pcv check valves are letting by which could be the reason its split in the first place.

I may be wrong but pretty sure servo is ment to get vacuum only, unless there is a check valve futhur up the line?
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ye the new switch doesnt need adjusting, the pin doesnt click in and out like the old one, its the new revised switch.

the picture below with the red line is the one thats split


Hmmm gonna have a look at this when i get home as i have an AMK and im pretty sure i dont have that?
ok, maybe it should go under that top boost hose, but let me know as im 100% sure mines a amk.
iirc that hose is indeed part of the pcv system and as far am im aware should not cause over revving?!

check out about half way down this page for a good picture and description:

i checked this, and noticed there is a oneway valve futhur towards the servo, which means that pipe it under positive and negative pressure where it split. So it will make it over rev, hesitant and hunt on idle if this pipe is damaged
ye just checked it, took the tape off and it started over revving again, what sportstractor said makes sense so replaceing it has sorted my over revving problem.:yahoo:
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it's maybe the strange connector pipe under the cross member near there master cylinder, mine has a jubilee clip on after it fell apart. It's like a 90 degree hard plastic push fit connector (ribbed)

You can follow the pipe from the inlet manifold toward the master cylinder.

Screenshot 20161117 220820
There was a re-call on the VAC pipes ? , I had to replace many of the pre-formed rubber hoses , they had splits in them , solved a lot of hunting , especially with the air-con pump on and over run when changing gear .. still not 100% convinced the brake servo is not being fed positive pressure now and then .. may be a new one way valve would help if there is one on the BAM engine
Mine has done this for12-18 months tried a few clutch switches , no fault codes ,new clutch never got to the bottom of it. Is there a way to test if the servo is getting positive pressure
seems to be issues round the break servo, some report it leaking vac - fixed with spraying silicone grease , past the in put shaft , other replacing it , not a simple job , audi seem to like vac valves , had problems with the 80CD years back and the strange pie-berg carb .. the ford xrx4xi was a pumped pressure system ... if I swap from acceleration to breaking .. sometimes I have a short [exciting] time before the breaks come fully 'on' ... with the engine off , I get about 30 seconds , before the vac has failed ... improved with new pipes

don't see any simple way to test for + pressure or leaks , without some rubber bungs , hoses and a sensor


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