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Test for boost leaks

Discussion in 'A3/S3 Forum (8L Chassis)' started by 1animal1, Aug 14, 2008.

  1. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Aug 14, 2008]
    Does anyone know of a simple test for boost leaks....i have checked where possible for split pipes but would like to make certain that no other leaks exist.

    I have read about certain smoke tests and pressure tests but haven't checked on what is associated and costs etc...anyones any ideas of these or similar tests
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  3. abdus
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    abdus Top Gear VCDS Map User

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  4. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Aug 14, 2008]
    cheers abdus, im gonna have to try and source a compressor and valve... definately a really good guide

    if any easier suggestions come up ill be interested
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  5. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Aug 14, 2008]
    just thinking out loud, im gonna try and source a 'bike' air valve tonight(threaded if pos might be a long shot)so that i can attach the car tyre compressor to the can...... needing a non return valve to rid the threat of back pressure once the system is charged upto 15psi
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  6. Jimmeh
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    Jimmeh Active Member

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    [Aug 14, 2008]
    Tim, if you have any joy with this, do let me know. I'm yet to check the obvious areas (TIP?) but am sure I am loosing some boost somewhere due to the max reading from a VAGCOM run being a bit off 'default'.
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  7. dansansome
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    dansansome Member VCDS Map User

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    [Aug 14, 2008]
    how about buying a bicycle inner tube and bonding the valve of that to the can (from the inside, so that when the system is pressurised, it aids the seal).

    you might be able to get your entire shopping list from halfords :)

    might try this myself....
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  8. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Aug 14, 2008]
    was thinking along the lines of a 'racer' tyre valve as they were always threaded all the way through and wacking two rubber seals together
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  9. mac1403
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    mac1403 Member

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    [Aug 14, 2008]
    I knocked this up for my A4. Maybe you could do something similar. Measure dia of the pipe off the airbox. Go to B&Q an get some plastic pipe the same dia and blank end plus some strong adhesive and if you can an American airline fitting (fits perfect onto a portable tyre inflator) I know its a bit Blue Peter ish, but it worked a treat on the A4


    [​IMG]

    [​IMG]
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  10. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Aug 15, 2008]
    cheers Mac..... where did you get the american air line from? i think the can will be the easiest to use as i wouldnt have to seal the end cap etc, but the valve is the bit with the question mark at the minute....never made it to bike shop last night, hopefully get to a halfrauds today
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  11. mac1403
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    mac1403 Member

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    [Aug 15, 2008]
    i might have one lying around if you send your address i will post it
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  12. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Aug 15, 2008]
    Cheers Mac, i'll give Halfrauds a go tonight, if i cant get ahold of anything ill pm you my address - really appreciate that mate
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  13. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Aug 25, 2008]
    okies an update...... i have made a unit using a can and a fully threaded valve from a push bike...... hooked it upto the TIP which is 80mm in diameter...the can is only 75mm (could be slight pressure loss here)

    ive used a normal compressor to push air in, noisey damn thing too!!! the pressure wasnt getting ver 2-3bar so think i either have aserious leak which isnt showing on VAGcom or i need something that will fit the TIP better.... once i removed the airline.... there is pressure holding as 1 minute later i released the oil cap which was under slight pressure..... just need to make sure the entrance unit is air tight, next step may be to replace the oil filler cap/neck.

    Mac.....what was the diameter of the pipe you used as i cant find anything except guttering that is 80mm, which you just so happens cannot buy a stopper cap for
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  14. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Sep 4, 2008]
    anyone got any suggestions on a can type cylindrical unit to fit onto the TIP....needs to be 800mm diameter...been to few DIY shops and cant find anything immediately obvious
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  15. Morgan-VAGCHECK
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    Morgan-VAGCHECK Foot to the floor

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    [Sep 4, 2008]
    Just one thing..

    You really do not want to be applying 2-3 bar pressure with this method !

    You could end up a very unhappy chap !
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  16. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Sep 5, 2008]
    Morgan, ive only tried this twice after MAF..... and both times noticed blue smoke for 1 minute on idle afterwards......

    Whats your thoughts on this....i have followed the instruction of the golf/A4 guys who have posted
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  17. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Sep 5, 2008]
    obviously the blue smoke prompted a slight leak of runny poo to dribble uncontrollably down my left leg only to enter the top of my sock and stop short of the heel....thank god for that!!!
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  18. HTC
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    HTC Active Member

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    [Sep 5, 2008]
    You are probably forcing pressure into the crankcase via the pvc system. I'd remove the PVC valve from the TIP and plug the hole before trying again.

    I wouldn't go above 30psi or 2 bar personally.
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  19. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Sep 5, 2008]
    HTC, what would the PVC system look like? may also be an option to pump air in here and block the air box off.......

    firstly what are the dangers of going over 2 bar, secondly will plugging the PVC system stop pressure building below the oil cap?

    apologies, im not the most experianced DIY mechanic:thumbsup:
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  20. HTC
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    HTC Active Member

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    [Sep 5, 2008]
    It's the pipework that allows the pressure and fumes from the crankcase during running to be sent into the inlet manifold and TIP depending on whether you are on or off boost.

    The pipe I'm talking about is the one that runs from the top of the cam cover on the passenger side to the plastic disc valve at the TIP. I'm not sure how how much pressure (if any) it can take in the wrong direction. You don't have to worry about the N75. When it's de-energised it connects the turbo outlet to the actuator which you'd want to test anyway.
    The one way valve at the front of the block under the inlet manifold stops pressure going into the crankcase so you shouldn't need to worry about that either.

    If you pump up the carnkcase too much then you'll be forcing oil up into places it wouldn't normally go. Past gaskets and past valve stem seals etc.

    You only need to test up to what you expect your maximum boost to be. I'm pretty sure testing as you have been with the PCV removed from the TIP and the hole blocked is the correct way. You won't get pressure under the oil filler then.

    Hope that makes sense.
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  21. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Sep 5, 2008]
    thanks HTC

    in summary i need to block the pipe from the TIP to the plastic disc valvey thingy, i gather i wont need to block the disc outlet as this is part of the vacuum system rather than the boost? having already put pressure through and having no running issues other than the previous problem (no VAG faults either), can i assume the valve is still intact

    one other thing ive noticed (not sure if this is part of the problem)is that when i secure the front boost pipe to the solid pipe that sits on top and to the left of the upper engine.... the pipe always seems to have slipped 2-3 mm, gonna replace the clip this weekend as its a bugger to tighten.
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  22. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Sep 5, 2008]
    buggar...... understand what your saying now HTC.... thanks again:laugh::thumbsup:
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  23. themanthatcan
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    themanthatcan Member VCDS Map User

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    [Sep 5, 2008]
    I think that's pretty normal Tim. Mine does it and most the engine-bay pics I've seen of the 1.8T have bee the same.
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  24. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Sep 5, 2008]
    think im gonna replace it anyway and whip the bumper off the next chance i get to tighten and secure everything....belt and braces
    #23
  25. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Sep 6, 2008]
    Jay, thanks for the tip mate, bought couple rolls of PTF tape to build the can seal up:salute:
    #24
  26. abdus
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    abdus Top Gear VCDS Map User

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  27. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [Oct 1, 2008]
    ^^ Thats what i have, he made a slightly smaller one to fit the A4 1.8t, Works a treat at only a few Lb. If you have a leak usualy its evident when you presurise. If its not hissing at 2 or 3 bar, it probably isnt leaking IMHO
    #26
  28. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Oct 1, 2008]
    thanks Abdus, i cant view it as cant get ebay at work.....still havent got around to checking mine yet although i agree with Byzan, 2-3bar should do it.

    After driving and monitoring the situation i think it only happens on max boost in 3rd gear mostly, this to me should hopefully indicate a boost leak but most liklely a pipe that needs tightening as opposed to split pipes...otherwise it would kick in all the time in theory of course
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