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Thread: PCV Valves

  1. #1

    PCV Valves

    I finally took the time to see if I could get the rear valve out of the head without rotating the engine. I had a pretty significant amount of oil getting past the grommet, and have had the new grommet for quite a while. Turns out, with a bit of force, the valve just squeaks by the frame. It doesn't look like the front will come out without dropping the front of the engine.

    My question is, how is the valve supposed to act? When I blew in either end, I didn't get a lot of resistance, and nothing moved inside with vigorous shaking. I'm assuming it is a one-way valve - from the head to the airbox - but I can't find anything on the Web that verifies that. I'd just buy a new one, but they're crazy expensive - at least $32 each!

    I ended up putting the valve in a US bath with mineral spirits for a while, then re-installed it with the (much tighter) new grommet.

  2. #2
    Senior Member 34nineteen's Avatar
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    Quote Originally Posted by Pushr0d View Post
    I finally took the time to see if I could get the rear valve out of the head without rotating the engine. I had a pretty significant amount of oil getting past the grommet, and have had the new grommet for quite a while. Turns out, with a bit of force, the valve just squeaks by the frame. It doesn't look like the front will come out without dropping the front of the engine.

    My question is, how is the valve supposed to act? When I blew in either end, I didn't get a lot of resistance, and nothing moved inside with vigorous shaking. I'm assuming it is a one-way valve - from the head to the airbox - but I can't find anything on the Web that verifies that. I'd just buy a new one, but they're crazy expensive - at least $32 each!

    I ended up putting the valve in a US bath with mineral spirits for a while, then re-installed it with the (much tighter) new grommet.

    If you look on here I think I copied TPEHAK's pictures of one that was cut apart. I think its just a small umbrella valve and a small filter.

  3. #3
    Senior Member Silverrider's Avatar
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    Tea bag ??
    teabag004.jpg

  4. #4
    Senior Member Barrett's Avatar
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    Steve: It's a one-way petal valve. Pretty common style of valve on many emissions/breather systems. When functioning properly, air should only flow from the cover side thru the valve and out the hose side....not in opposite direction. Single flow direction keeps atmospheric contaminants out of the engine internals and theoretically generates more crankcase vacuum freeing up HP....so I'm told.

  5. #5
    Barrett - thanks for that! So it is actually a PCV, and not just a 'breather'.

    Well, I have at least one bad one. You'd think they'd last more than 13 years!

    I'll put a watch on eBay for a couple that aren't stupid expensive. It's not the cost - it's the principle. That's Mercedes/BMW pricing!

  6. #6
    Senior Member Barrett's Avatar
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    Yes sir Steve, you could call it that. Over time, what shortens their lifespans is the intensely hot environment they reside in and the stress/pressure of the hose bend placed upon them. Used might pop up on Ebay.

  7. #7
    Senior Member Cooter's Avatar
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    Small note. An umbrella valve like in that passive PCV system won't perfectly seal with a 'breath test' like that, and frankly doesn't need too. It's meant to survive millions of pressure waves in a hot and oily environment and needs to be effective, not perfect.

  8. #8
    Cooter, there's almost no difference which end you blow in - very little resistance.

    What little there is might probably be the foam 'oil trap'.

  9. #9
    Senior Member 34nineteen's Avatar
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    FFS people. It’s like Facebook around here.


  10. #10
    I think I've seen that pattern on a video game!


    Yeah - there's no way the valve I've got is working properly. The 'umbrella' looks like it seals against flow 'downward'. Mine has little restriction both directions.

    I checked at the local HD dealer - the part is 'obsolete', but listed. Last price was $35 and change.



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