High cam cover pressure

Discussion in '8-valve' started by rich81, Aug 5, 2011.

  1. rich81 Forum Member

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    I've been having a problem with the rocker cover leaking since I fitted a 2E bottom end with PB head into my mk2 digi. I ended up fitting a mk3 rocker cover with mk3 rubber gasket to get a decent seal yet still had a bit of a leak down the back. Today whilst setting up the idle I removed the PCV ufo thing from the rocker and oil started ****ing out of the rocker cover down the front and back!

    I have heard about problems with rings causing high crankcase pressure but the crankcase breather isn't the issue here. There is a good blow of air coming out of the hole in the rocker for the PCV ufo when removed, but I'm not sure if it is normal or too much. With the breather system all connected up properly, with the crankcase also connected, the rocker gasket is only leaking a little bit, as though the vacuum is helping keep the pressure down, but you can still feel some air escaping through it at the front.

    Interestingly it seems to be only at idle as when I rev the engine the pressure in the cam cover seem to go down, and whilst driving it doesn't seem to leak, only at idle... Incidently the engine is running sweet and doesn't appear to be burning any oil.

    I'm wondering if the valves are not seating properly which could be causing the head to over-pressurise...

    I will take the plugs out to inspect tomorrow and try to get hold of a pressure tester as well.

    Just wondering if anyone has had issues with this before?

    I'm thinking of perhaps putting some sealant on the rocker gasket to help it.
     
  2. mark25 Forum Junkie

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    You're not supposed to do it like that, you're supposed to leave it fitted, but disconnect the outlet so that the PCV vents to air. Then you need to block the open pipe going to the engine inlet. Is there anything comming out of the PCV outlet? maybe it's that that's blocked/broken?
     
  3. Mike_H Forum Addict

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    ^^ What he said. Sounds like a blocked breather valve to me.
     
  4. rich81 Forum Member

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    Thanks for the input I've done some more investigation this morning. Firstly I've left the PCV on and removed the pipe from the crankcase breather (clamped the pipe first to keep the PCV circuit sealed) to see how much the crankcase is breathing. This seemed fine with just a very small amount of breathing through there.

    I then reconnected it all and took the oil cap off with the engine running which also seemed normal, not enough breathing to lift up the oil cap and probably more suction than blow. Revs drop slightly with this removed.

    Then I found that if I squeezed the pipe which goes from the PCV ufo to the throttle body, the revs would drop a bit and small amounts of oil would spit through the rocker gasket. I'm expecting this should have happened as the system is then all sealed with nowhere for the pressure to go!

    I am using the mk3 gti PCV with the two outlets on and I have a spare - is there a way to check the operation of this? I assume it is basically a one way check valve.

    I noticed that when the engine was turned off, there seemed to be a moment where some oil seeped out of the rocker gasket, as though there was some pressure there but the engine had stopped drawing air so it had to escape through the gasket.

    I'm wondering if this is just because I have fitted a GSF rubber gasket and I should have gone with a genuine VAG one... [><]
     
  5. rubjonny

    rubjonny Administrator Staff Member Admin

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    did you also change the studs for new ones without a shoulder? because if not thats probably why...
     
  6. rich81 Forum Member

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    Yeah I changed them. Looking at it now I'm thinking it's a just a crap quality gasket so I will try a genuine vag one before wasting much more time on it. [8(]
     
  7. rubjonny

    rubjonny Administrator Staff Member Admin

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    cool yeah does sound liek a poor quality gasket, though used gsf before and ok. but they'ere a bit hit n miss, got a cork one and it was nowhere near right, totally wrong shape
     
  8. rich81 Forum Member

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    Update: In case anyone else searches for a similar problem, this was completely solved by fitment of a genuine VAG rocker cover gasket.

    I did suspect the GSF gasket as the rubber seemed quite hard and the half moon bit didn't seem to fit well.

    The genuine VAG one is much better as it's thicker with deeper channels and softer rubber, and fits perfectly. Just torqued up lightly to about 7nm and all is well :)


    I normally rate most parts GSF sell but steer well clear of the rubber rocker cover gaskets!!
     
  9. MK21800 Forum Member

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    Good to hear. I've just fitted a VAG rubber one. I had a seperate issue though which was that a couple of the "normal" (dark short) studs they gave me were really tight into the holes, so much so that it might have been on the verge of stripping the threads. I took these out and replaced with the longer brass coloured ones, which went in absolutely fine, so mine's a mish mash of long and short studs now.

    Did you do your nuts up to the same kind of tightness as the cork one? I was thinking maybe the rubber one would allow an extra pinch or two as it has those metal spacers acting as stops.
     
  10. rich81 Forum Member

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    The thing with these gaskets, cork or rubber, is you really need to be careful not to over-tighten them. This is especially important with the mk2 style rocker covers, which warp easily. The nuts on the rubber one tighten down quite positively but I only did them to about 7nm, which really isn't a lot. It's difficult to express how tight to do them but I would say a light-medium pressure with a 4-5inch ratchet handle is about right. You certainly don't want to be swinging on them or pulling very hard.

    As long as the studs you've used haven't got the shoulder on and they are long enough then they should be fine. I fitted a mk3 rocker cover onto mine and had to fit a slightly shorter stud where the fuel pressure regulator is to get it to fit.
     
  11. MK21800 Forum Member

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    I'm thinking holding the ratchet in the middle almost like a palm ratchet might help in not overtightening them.

    Yeah seems to be an issue doesn't it with the Mk2's - this weeping rocker cover. It's a pain. So if the cover is warped then what are the options there? I'm presuming that's why you fitted a MK3 cover.... or was that just for aesthetic purposes?
     
  12. rubjonny

    rubjonny Administrator Staff Member Admin

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    its actually not possible to over-tighten them, because cork gasket studs have the shoulder, and rubber gasket has metal rings in. so basically you tighten till you feel the nut bottom out on stud/ring, then lightly nip up.
     
  13. rich81 Forum Member

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    I fitted the mk3 one as I was having no luck stopping the huge oil leak from there and when I dropped a straight edge on my mk2 one it was no where near flat. It seemed to have been damaged by overtightening as the area around nuts was sunk down towards the head surface about 1-2mm compared to the flat bits inbetween the bolt holes. I straightened it all out to nearly flat but it still leaked. The mk3 one is a lovely flat machined alloy surface so this helps. However, even this leaked badly with the GSF rubber gasket. Only the VW gasket cured it and it may well have been ok with the straightened mk2 cover.

    I know what rubjonny is saying about the shoulders so in theory this makes sense however I have definitely seen a few overtightened and damaged mk2 rocker covers. My mates' mk2 is in the garage with the same problem at the minute. Perhaps some of the cheap gasket don't have the correct height washers or something.
     
  14. rubjonny

    rubjonny Administrator Staff Member Admin

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    that can happen if you dont use the 2 metal spreader bars :)

    oh and a tip for anyone using an alloy rocker cover on a digifant. don't bother with studs at all! use bolts instead. trust me your life will become much easier :lol:
     
  15. rich81 Forum Member

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    It might just be that the mk2 covers get warped over time and not by over-tightening... but the mk3 one looks good (providing you paint/polish it) and gets you a nice seal
     
  16. rubjonny

    rubjonny Administrator Staff Member Admin

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    i recon using a gasket slightly too thick and/or not fitting the 2 metal spreader bars would cause this, age and metal fatigue prob also play a part. whatever the casue the way forward is alloy rocker cover plus rubber gasket. as well as the nice seal you get and better looks, you also have a much better timing mark to work from for your cam sprocket :thumbup:
     
  17. Bengaard DK DUB New Member

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    Hello Everybody.
    After reading extensively on here for years, sucking an abundance of knowledge clarifying many mysteries,
    I feel the time has now come for me to start asking my own questions.
    So, can anyone tell me if the mk3 / corrado alu covers per above are taller than the mk2 ones?
    Will they fit under the stock airbox on a 1,6 carb engine?
    And will a hockey puck PCV valve work as replacement for the mesh filter built in the original?
    I´m all exited to start actually communicating with this wast bank of vwwisdom.
    Greetings from Denmark.
    Bengaard.
     
  18. rubjonny

    rubjonny Administrator Staff Member Admin

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    they are a little taller yes, you might struggle to get the airbox back on. that plus the pcv hole is on the opposite side to the carb airbox outlet so routing the breather would be tricky. personally I would save the money and ut it in the 'better engine' moneybox ;)
     
  19. Bengaard DK DUB New Member

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    Thanks for answering.

    Seems some are the right way round..
    https://www.ebay.com/itm/VW-CORRADO...537419?hash=item28a25a95cb:g:4xwAAOSwa6Jfs6a1

    ´Thing is, I´m having a similar problem as OP. Oil from breather in air box leaking onto intake manifold. I´ve gathered so far that i have to clean the mesh inside the cover. Might also help some hesitation and rough ideling at startup? (Also bought comp/leak down tester, got 390K on it).
    I would really want to sand and paint it while its already off but the car is my daily and most times only having few hours at the time in the borrowed workshop, I tend to prepare every operation so it´s as plug and play as possible. And then i´m tempted to make the cosmetic upgrade while at it.

    As for the `better engine`hint; I know, I know, but when I bougt it 5 years ago i did´nt, and now i´m attached. (My first vw)
    The whole project has long since left the realm of reason.
    Actually I´m in so deep that I´ve already got the GTI cam, manifold, downpipe and Weber 32/34 laying around just waiting...
    By the way do you think a K&N pancake will fit over the alu cover?:lol:
    Bengaard
     
  20. rubjonny

    rubjonny Administrator Staff Member Admin

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    thats a G60 cover, the hole is on the right side for those but you have the added G60 tax on top over the normal 2.0 8v ones :)

    the k&n will fit over the cover no problems but you wont gain anything over the proper airbox
     

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