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Which Check valve for catch can install

Discussion in 'A3/S3 Forum (8L Chassis)' started by Gizmo20VT, Jul 3, 2012.

  1. Gizmo20VT
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    Gizmo20VT Member

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    [Jul 3, 2012]
    Hey Peeps

    Need some assistance, I installed a catch can last week and deleted all the PCV lines under the intake manifold.

    My car seems to have a really terrible idle and overboosting randomly, VAG code 17705 Pressure drop (checked DV already).

    On the oil catch tank DIY's I see that they installed additional or original check valve back in place, could anyone shed some light on this? What size valve and which direction it would face?

    [​IMG]

    All of this was removed including the check valve

    [​IMG]
    Last edited: Jul 3, 2012
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  3. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Jul 3, 2012]
    Ok... thats the servo vacuum hose and you don't need that check valve in it as S3's have a check valve by the servo...

    If you are having the problems you say then I would suggest you have a vac leak... under the inlet manifold there are 3 vacuum outlets, 2 small ones above the alternator and one larger one in the middle...

    The 2 small ones feed the DV/N249 and the FPR... the larger one feeds the PCV system... to do a proper 'delete' of those pipes you need to bung the middle outlet, replace the 'T' (06A 103 247) with a straight piece of hose (silicon or rubber) or block the PCV valve properly...

    Pull the servo hose from the pipe work (red circle) and connect direct to the outlet on the side (as per you pic above)...

    <tuffty/>
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  4. Gizmo20VT
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    Gizmo20VT Member

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    [Jul 3, 2012]
    Hi tuffy, thanks for the response.

    I have used a 8mm vacuum cap for the center underneath the manifold, two small nipples feed the FPR and DV as stated in your post.
    My Catch install is done per the DIY's, but both DIY's i've seen have the additional check valve installed. Will do a leak test on the weekend but most rubber pipes have been replaced with silicone pipes and boost pipes are running T-Bolt clamps.

    Unless the 1 check valve behind the head is faulty?
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  5. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Jul 3, 2012]
    Plausible... follow the pipe work for the servo back from the inlet and the servo check valve is behind the heat shielding on the bulkhead by the servo and should itself be wrapped in a bit of silver face fibre glass cloth... to check it, cap off the servo outlet from the mani (don't drive the car just let it idle) and see if the idle improves... personally I don't think this is it as it was ok before you did the delete...

    I would be checking all the hoses again tbh just to be sure... air is getting in somewhere...

    <tuffty/>
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  6. Gizmo20VT
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    Gizmo20VT Member

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    [Jul 3, 2012]
    Agreed, i did remove the servo hardline last night and blew in both ends, Valve does work but not sure what pressure it can hold. Will See if I can pressurize the system tonight with some soap water. Will report back in the morning. Thanks for the response once again Tuffy. :happy:
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  7. Gizmo20VT
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    Gizmo20VT Member

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    [Jul 6, 2012]
    Alright, been doing some logging and correcting some errors that i created myself.

    Pressure Drop code is sorted - I realigned the TB butterfly, had to loosen the 2 torx screws inside and make sure it seals properly. Idle is smooooooooooooooth :jump:.

    But the over boosting is back, also multiple missfire on coilpack 3 while trying to log.. Could this perhaps be the cause of overboosting cause the previous night the car boosted its 12psi and just went into limp constantly..

    Have some logs if anyone needs them to assist, i logged group 115 & 118 & 003 but cant really push the car much cause of the PSI increase. I did check the wastegate and its set to 6 PSI (Pressure tested)
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  8. Gizmo20VT
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  9. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Jul 6, 2012]
    When you say loosened the torx, you have done them back up? there is supposed to be a little gap... leaving them loose will lead to them being ingested by the engine and spat out through the exhaust potentially damaging the engine and the turbo on their way through...

    Looking at the log... actual is looking like actuator pressure to me... request is trying for boost but due to the negative deviation (not meeting request) I believe thats where the code is coming from...

    You say your car is boosting to 12psi? there is nothing in that log that suggests thats happening...

    <tuffty/>
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  10. Gizmo20VT
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    Gizmo20VT Member

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    [Jul 6, 2012]
    I have tightened the torx bolts again, I stripped the TB for powder coating so all is good there now. The problem with those logs are that the boost was not controlled, the boost went as high as 20PSI + then i backed off and then the coil pack started acting up.

    Also tested another N75 valve and the duty cycle is not constant...

    Currently the car sounds like a scooby, definitely running on 3 cylinders, waiting for a spare coil pack to replace mine and will see what the boost does form there?
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  11. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Jul 6, 2012]
    Coil pack should affect the boost... what I would try next is electrically discoinnecting the N75 and do a run or two like that to see if boost settles... should just sit on actuator press and not complain...

    I assume you have the N75 pipework connected correctly?

    <tuffty/>
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  12. Gizmo20VT
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    [Jul 6, 2012]
    Yip Long piece into TIP, opposite end to Actuator, middle nipple to manifold pressure. :)
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  13. Gizmo20VT
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    [Jul 7, 2012]
    Fitted a new set of beru TT coilpacks this weekend and new plugs, no missing and car pulls strong, currently the car is boosting 19psi, is this correct according to the logs posted above in this topic? CMD is going up to 2000+ and if i work it out correctly that is 1.2+ bar.... Would I be correct in saying the car has software loaded on it? Tested with another N75 and same result, slightly higher in Boost by 2-3psi.
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