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I stripped my Forge DV down as i wasnt sure if it was leaking... Advice needed please

Discussion in 'A3/S3 Forum (8L Chassis)' started by S3 Paul, Jan 19, 2013.

  1. S3 Paul
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    S3 Paul Moderator Moderator

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    Well after reading Jardo's thread about the Forge DV and that its prone to leaking boost i thought as mine had been on a while i would try the bubble test...
    Basicaly i used a bike pump to preasurise the DV as instructed by Jardo... after just one pump there was bubbles leaking out of the bottom. Bad news...
    So i stripped it down to check the insides.
    This is what i was faced with...
    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    Sorry for the quality... iphone
    The ring at the bottom of the piston is clearly worn but could it be lapped out with grinding paste method,
    There is next to no wear on the inside of the DV body,
    the marks on the side of the piston... is this damage or how they come?
    the spring looks a little battered? or is this fine and not something to worry about ?

    Thanks for any help.

    Paul
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  2. superkarl
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    superkarl MAN OF STEEL

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    Lap it in with paste, and as tuffty has been recommending, use a green spring with a shim.
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  3. 16Klappe
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    16Klappe Princess Slayer

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    Hmm, so with pressure in the top nipple and the side port it leaked quite readily. Sounds bad.

    As SK and myself have instructed a valve grinding dowel and some valve grinding paste to re-face the piston in the body will be the best idea.

    Did you use grease on the o rings rather than light oil as I said? Sometimes they can cause the valve to stick slightly.

    A green spring and a shim (to lower the cylinder volume) should be enough.

    Dare I say it...Try an OE valve.
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  4. S3 Paul
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    S3 Paul Moderator Moderator

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    so... Slowly lap the piston in against the body ?
    bottom face obviously , then before refitting I need to buy a green spring and a shim?
    with any luck I will be picking up a standard DV tomorrow if its not faulty I will fit that,
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  5. S3 Paul
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    S3 Paul Moderator Moderator

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    Am I right in thinking its the " valve tuning kit"
    I need from forge?
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  6. Prawn
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    Prawn My other car is a MINI!!!!

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    you need a forge service kit, which consists of 2 o-rings and some grease, then some generic lapping paste and a stick with a suction cap on the end.

    The bit you need to lap in is the conical end of the piston. You can see the mark on yours where it has been making contact with the seat.

    On a fully lapped piston, that band will be a full 4mm wide to show it's making complete contact with the piston seat and sealing fully. A narrow band suggests it's not well fitted and highly likely to leak.

    Try lapping it in well, and also if it's got the hexagonal top try sealing up the side port where it scews in as well, they often leak from there.
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  7. S3 Paul
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    S3 Paul Moderator Moderator

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    Thanks,
    the O rings look fine, I've checked them for any damage.
    Is the side port just screwed in?
    i didn't want to try and force it , seal it with? Silicone on the threads? Ptfe?
    i will lap the piston to the seat in the morning .
    deffo a shim and new spring?
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  8. Prawn
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    Prawn My other car is a MINI!!!!

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    if the top it hexagonal, then yea, the side port is screwed in.

    Tough to say what to seal it with, I've not done mine yet, and I'm certain it'll be leaking!

    Lap the piston until you've got a clear and clean 4mm seat the whole way around.

    I run a yellow spring and shim with my hybrid, seems perfect. Just try adding a shim to yours with the yellow spring.

    When you fit the shim, I used a little sealant on the bottom of the shim on mine, to totally seal it off from the cavity that remains below the piston, just to ensure the chamber volume is reduced.
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  9. A3 T
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    A3 T Lord Of The Rings

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    I'm i bit confused about all this lapping the piston stuff....lol


    Wouldn't lapping the piston make it harder should he need to renew the piston at a later date ?
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  10. 16Klappe
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    16Klappe Princess Slayer

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    No.

    Eventually he would need a new piston...But that would take decades.
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  11. A3 T
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    A3 T Lord Of The Rings

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    But wouldn't the paste also grind away at the body of the valve or am i looking at this completely the wrong way ?
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  12. superkarl
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    superkarl MAN OF STEEL

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    The bottom of the piston is what youre lapping with paste, it needs a good seal, lapping it with grinding paste ensures a uniform seal all the way around.
    Compare it to the lapping of valves in a gead, and the seal between valve and valve seat, needs to be bang on all the way around.
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  13. A3 T
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    A3 T Lord Of The Rings

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    I'm currently using a baily dv30 but I've got a 007 on its way.

    It will probably be clear when i take it apart....lol
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  14. vanilla_ice
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    vanilla_ice Member

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    So grind out the line shown on the second photo to 4mm wide?


    Does anything need to be done to the band caused by O-rings shown in the first photo?
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  15. Prawn
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    Prawn My other car is a MINI!!!!

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    BANG ON :applaus: Somebody gets it ;)

    That line as seen on Pauls, is where the sealing is occuring against boost pressure.

    On Pauls it's a very thin line. On mine after lapping, it's a full 4mm thick seat
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  16. S3 Paul
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    S3 Paul Moderator Moderator

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    I've just had a quick go at lapping the piston.
    out of interest are we looking for a fully dull 4mm? Like you would a valve in a cylinder head?
    ive tried to remove the side pipe but to say its tight is a massive understatement ,
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  17. Prawn
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    Prawn My other car is a MINI!!!!

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    yes a nice dull band paul.

    Is your valve a hex top or round top? Only hex top ones are removable I think.
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  18. S3 Paul
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    S3 Paul Moderator Moderator

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    It's hex topped . I can see its threaded but without damaging it by clamping the pipe in some soft jaws I don't think it's going to budge too easy,
    i will give it another go when I venture outside ,
    i used a little rough paste to make a start on the seat I've just cleaned it down before I swap to fine ppaste the band is now 4mm but has a few lines from the rough paste...
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  19. Prawn
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    Prawn My other car is a MINI!!!!

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    Sounds good mate. it's a huge difference compared to your first pic isn't it? The two faces are very very closely machined, but obviously not perfectly.

    Bigger the seat the better the seal :)
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  20. S3 Paul
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    S3 Paul Moderator Moderator

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    Well...
    just tried it with bubble test...
    bubbles galore , out of both the end and the thread on the side,
    great news... Not
    i just hope that the standard valve is available today and that its not split,
    big asks I know for a Sunday but I need the car for the morning
    #20
  21. badger5
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    badger5 RIP S3dave Site Sponsor

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    Is this how you tested it Paul?
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  22. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    <tuffty/>
    Last edited by a moderator: Aug 15, 2014 at 10:19 PM
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  23. s3clarke
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    s3clarke Money grabbing s3!

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    Well after reading the same post as the op, I can confirm I have taken my round headed 007 off my s3, checked the piston for leaks with the pen trick, finger over the nipple job, and the piston just drops back down. Great news! I've just put the oem dv back on, which I think I'll be leaving on as that was spot on no leaks etc. Also... My forge dv has a blue spring.. I brought it second hand and never checked it, just put it on, until recently with all these dv posts I've realised they have a few different springs and need servicing every so often. What do u suggest? My car is basically standard and if I play with it, will only be going to the 270-280bhp mark. So for hijacking, just didn't want to raise a new post for the same issues. Cheers.
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  24. S3 Paul
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    S3 Paul Moderator Moderator

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    I beleave so... i used this...
    to put equal air preasure to both the SIDE and to the TOP small fitting.
    The valve leaked straight away with only 1 pump of my cycle pump,
    [​IMG]

    Is this correct or wrong?
    I cant see a second pipe going to the top of the DV on the video tuffty posted???
    #24
  25. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    In fairness the ECU is pretty intelligent... as its a load based ECU it can cope with minor leaks by increasing boost as compensation... load based ECU's don't have 'boost' tables... they alter boost to achieve the requested torque from the driver... this is why you see higher boost levels during the summer than during the winter as the ECU requests more boost to compensate for the less dense air to meet the torque request...

    What this means in real life is that the small leak that some of these valves have won't have an adverse affect on performance... no leaks are better but for the most part (unlike some of the chinese copy valves I have seen) its not going to change your life...

    <tuffty/>
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  26. s3clarke
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    s3clarke Money grabbing s3!

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    Gave it a quick clean, used cutting paste on all the worn marks, regreased it and put it back together, this time the valve drops a little then holds. Think I will stick either a green or a yellow spring in which ever is recommended on a standard 225, with new o rings and either try it again or if I am happy with the oem valve I will sell the forge.
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  27. S3 Paul
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    S3 Paul Moderator Moderator

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    Well... I fitted an oem valve ( that passes the pen test) and now the car will spike round to 22 psi but drops to 15 psi every prolonged pull?
    duff valve?
    car fecked?
    im sick of this car, it's always something
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  28. A3 T
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    A3 T Lord Of The Rings

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    I don't suppose you have a how to lap the forge valve video do ya ....lol
    Last edited by a moderator: Aug 15, 2014 at 10:19 PM
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  29. S3 Paul
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    S3 Paul Moderator Moderator

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    When lapping in the piston seat did people use the o rings to centralise the piston? Or just allow it to self centre ?
    Can somebody confirm how I tested the valve was right?
    i asked a few times and tried to read all the threads...
    #29
  30. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    Connect the alloy bit of your tester to side inlet of the DV (one that sees boost when fitted the correct way round) and then the blue tube coming from the side of your tester to the vac inlet on the top of the DV... pressurise through your valve as normal...

    The side port should undo on the newer 007p's... I used thread lock initially on mine but still leaked... so then I used 100deg c silicon... all good now

    <tuffty/>
    #30
  31. 16Klappe
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    16Klappe Princess Slayer

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    Push the piston of the OEM valve up and place your thumb over the top nipple. Look through the side port and see if the seal drops.

    If it drops it is ****ed, if it stays firm it should be fine.
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  32. S3 Paul
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    S3 Paul Moderator Moderator

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    ah,
    well it holds vacuum,
    It doesn't hold fully open but it doesn't drop all the way. When I remove my finger it snaps shut,
    is the forge DV repairable ? Or is it beyond messing about? It leaks with the "pen test" and drops to about 4 mm from the bottom until I move my finger.
    #32
  33. badger5
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    badger5 RIP S3dave Site Sponsor

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    its always going to drop a little.. Normal..
    Air is compressable.... and flip side of the coin is its als "Stretchy" so the drop is the DV's internal volume being stretched until its pulling a vacuum to hold it... hence the movement.

    you will notice a stock DV hardly moves down on its pen test as its internal volume above the diaphragm is smaller than on a forge.

    forge do a service kit.
    o rings and grease.
    #33
  34. rraghvani
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    rraghvani Whoever does not try, does not learn.

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    The Forge 007 DV (blue spring) is great, had mine for around 10 years. I service it every year, using engine oil (I find using the red grease dries up to quick) and never had any problems. There’s instructions up on the Forge website that shows how to maintain and leak the DV.
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  35. badger5
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    badger5 RIP S3dave Site Sponsor

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    blue spring? does it open at all?
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  36. 16Klappe
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    16Klappe Princess Slayer

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    My valve used to operate "well" with a blue spring.
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  37. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    I dunno... you don't need a stiff spring in the DV... end

    <tuffty/>
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  38. badger5
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    badger5 RIP S3dave Site Sponsor

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    lols.........

    oh no not again :p

    "well".......... the well know exacting description...

    hehe
    #38
  39. 16Klappe
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    16Klappe Princess Slayer

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    Pmsl.
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  40. A3 T
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    A3 T Lord Of The Rings

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    Here's a video guide showing you how to service the forge valve (i don't think you should use vaseline to grease it):





    It would be good if someone on here would do a guide on how to lap the piston :)
    Last edited by a moderator: Aug 15, 2014 at 12:29 PM
    #40

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