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brand new PCV valve leaking..

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  • brand new PCV valve leaking..

    Hi guys,

    Doing a full boost-circuit check on an RS2 I found that the PCV valve (035103245a) was leaking heavily.
    Took it out, cleaned it nicely, and when putting my mityvac directly onto the PCV valve it now leaks out from 2bar to 0 in about 15sec... so a small leak remains.

    I said hey, for what it costs I'll order a new one. Got a Febi one and on that it is impossible to build up any pressure... even hand-pumping very quickly can't generate anything about 0.3 bar and bleeds directly to 0.

    So the 25 year old PCV valve is better than a brandnew one!

    Are these known to remain leaking a small bit (due to the crappy plastic disc design) or should they be completely tight when pressure testing?


  • #2
    Yes, Bosch should be a lot better. Tested mine just after purchasing it brand new for A4 B5.

    FYI, 035103245a oem costs about the same price as Febi crap.

    Sent from my SM-J510FN using Tapatalk

    Last edited by Val; 7th August 2019, 10:03.
    5vtq gte


    • #3

      After some reading I just filled it with strong 2k liquid plastic to remove its function, and have it 100% leak free.


      • #4
        For what its worth 043 Motorsports sells a billet version:

        The silicone hose to fit:

        The Silicone T hose:

        I not a big 034 Motorsports fan but have had good luck with this valve; as far as I know it still functions great after 5 years.
        //-\\ ((_)) //)) //


        • #5
          I've read about some of those billet 034s getting stuck, so I didnt want to take the risk.

          Since the IM pcv source isnt really needed apparently it seemed like the safest option to cancel it out. N80 ofcourse still remains active


          • #6
            I have bought 4 genuine non return valves from stealer.All of them not stayed 100% sealed when pressurlized.the best way is using some other check friend is using the non return valve from the toyota brake vacuum booster.
            one of a few I5 from Asia.


            • #7
              Fixed a few little boost leaks apart from blocking the PCV valve and the boost leak test was now great... bleeds very slowly and no more leaks.

              Went on a testdrive and it hit right at 1.9bar target boost, very crisp, and goes like stink. But after a few pulls it started to misfire when reaching full load at 3-4000rpm with 1.9bar starting from higher gears. Dropping a gear and starting from 4500rpm (and thus only going to 1.6 or 1.7) it goes fine. Going flat out in 2nd-3rd-4th all no problem... just the starting in low rpm and reaching the full boost made it unhappy.

              scanned for codes and got 00537 and 00561. Aha, boost leak?! Pressure tested it up to 1 bar and it's perfect, no new leaks. I did find (luckily!) that the inner ring of the intake hose had come loose (see pic)... could that cause it?

              Starting to think if the blocked PCV valve would be a cause, but that cant be?

              Also thought about my rebuilt wastegate thats getting jammed, but it reaches and regulates its boost perfectly under all circumstances. Doesn't overshoot.

              a crappy video from the misfire


              I'm thinking about a coilpack? It idles and runs great for the rest.

              Thanks for the help!!

              Last edited by Avantus; 14th August 2019, 10:51.


              • #8
                Forgot to mention that the car has a 1.9bar WG spring installed. Wound up to flush with the cap, but maybe the rate at which the boost comes in at 3-3.5k rpm in 3rd gear and up is still too much for the ECU to handle? n75 is new btw.


                • #9
                  Installed an original rs2 spring and it's perfect now. The 1.9bar spring was fully wound out but still too much for the ecu software it seems.


                  • #10
                    Awesome, happy to hear you sorted this out. It can be frustrating chasing down a running issue. But totally worth it once resolved.

                    So you just blocked the valve solid? This has no ill effect? I know nothing about it's function.
                    //-\\ ((_)) //)) //


                    • #11
                      Yes valve is solid now with no function. Apparently it really isnt needed, and being a major boost leak source its always good to cancel it out for good.