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    #1

    Valve seals failure

    While cruising with some friends, I've been notified that my car has been blowing blue-ish exhaust smoke when downshifting and hard accelerations. Especially if I'm coasting for a bit before I downshift, i.e. coast in 4th, then blip downshift to 3rd for acceleration. Recently did a cold compression test and all cylinders came out 160-170 PSI, the car feels powerful and pulls hard. I've also been burning about 1L of oil every 2500-3000KM. The symptoms seem to lead to bad valve seals/guides based on my research, as during engine vacuum (coasting), oil gets sucked past the valves and into the cylinders, which is burned off when I "blip" downshift.

    Is this a known issue on S54s?

    Seeking advice.. Is this something I should address immediately? Was actually planning to do my VANOS overhaul but since this came up it might be good to do it all, with head gasket too perhaps.
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    #2
    Have you done a leakdown test? That would confirm your theory on valve seats going back. As far as I know it is not a common failure point with the S54. How many miles/km?

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      #3
      Originally posted by eacmen View Post
      Have you done a leakdown test? That would confirm your theory on valve seats going back. As far as I know it is not a common failure point with the S54. How many miles/km?
      Good call on that, so a leakdown test will uncover valve sealing issues? 153K km so about 95K miles.

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        #4
        Originally posted by eacmen View Post
        Have you done a leakdown test? That would confirm your theory on valve seats going back.
        I think OP suspected a valve seal, not a valve seat. Not sure how a leakdown test could identify a bad valve seal?

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          #5
          Originally posted by LightlyToasted View Post
          I think OP suspected a valve seal, not a valve seat. Not sure how a leakdown test could identify a bad valve seal?
          Yeah it won't be able to identify a problem with the seals. It will rule out piston rings though, making valve seals a much more likely culprit.
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            #6
            Originally posted by dl.m3 View Post

            Good call on that, so a leakdown test will uncover valve sealing issues? 153K km so about 95K miles.
            Sorry late night reading without glasses. Leakdown will only test if the valve is leaking at the seaT not the seaL. Apologies for the confusion. I am not aware of a good test for the valve seals other than ruling out piston rings, which a leakdown test will do.
            • Likes 1

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              #7
              Inspection camera down its throat might help see something

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                #8
                Do you have a rattle/“pinking” noise at ~2-3kRpm?

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