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b5 s4 AIR LEAK

S4SIMON May 11, 2008

  1. S4SIMON

    S4SIMON New Member

    Recently noticed boost trim/limp home mode had kicked in - specialist read fault code for 'air leak' and replaced a small hose free of charge & reset car - fine for a few days. Happened again and two air leak codes came up - morning at garage and two hoses replaced. Twenty minutes of driving later and you guessed it - same story. Booked in for tomorrow - but I'm wondering if 1) this could signify something more sinister and 2) doesn't VAG-COM tell you where in the system an air leak is making it easy to locate and fix? I notice there are absolutely bloody loads of little hoses all over the engine so I'm worried this is going to hurt, labour cost-wise. I asked about simply changing the full set of hoses but since there are so many I was told it would cost fortunes....

    Worried of East Anglia
  2. stapo69

    stapo69 All hail the mighty quattro!

    If it's boost hoses that are leaking try a fullset of silicones off ebay, autobahn88/zena racing ones from hong kong, 100 notes gets the fullkit, got a set on mine with no real probs at all, replaced them all as I had 2 different ones go in the space of 2 weeks. Samcos go for around £300, but I really couldn't tell much difference at all.
  3. Blue_Thunder

    Blue_Thunder Well-Known Member

    Vagcom isn't that smart. Won't always throw a code either.

    Ideally you need to do a pressure test. This involves placing a pressure tester (basically a big plastic bung with a valve) over the Y-pipe and pressuring the system with a compressor to about 10-15psi. If there are any leaks, you'll hear them.

    Likely suspects for pressure leaks in the S4 are from the F-hose, TBB, intercooler end caps and also faulty one-way valves can cause problems.
  4. S4SIMON

    S4SIMON New Member

    Cheers for that. They called today to say that the air leak fault codes aren't coming up any more but a fuel trim one is. The seem to have been pretty methodical about it and the MAF readings they're getting are well outside the normal parameters.
    So they're replacing the MAF tomorrow, and think that should do it.

    My worry is that this might all be linked to the generic remap I had done in january, but only time will tell.

    Fingers and everything else possible crossed.

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