compression test question...

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  • quillbro
    Grease Monkey
    • May 2006
    • 369
    #1

    compression test question...

    Hi all,

    Trying to start my first ever swap project and in looking for a motor i found this....s52 motor that was in a crash out of a 99 auto convertible. I asked the guy to do a compression test on it (the motor has 67k miles) But He said that he cant because the oil pan is cracked.

    I said ok, but later thought to myself, Doesn't the compression test measure the amount of air compressed between the valves and the piston rings? I don't see how the oil pan comes into play.

    Anyway, wondering if you guys can shed some light on that.

    Also on another disassociated note, The motor got a broken fan, cracked oil pan, and broken tranny mount that was welded back on from the crash. Do you think this motor could have internal damage? And if so is there anyway to find out? Its just sitting on a pallet right now.

    heres the carfax if anyone is curious.
    http://www.carfax.com/viewEmailRepor...i3&language=EN


    Thanks for the input, I really appreciate it as Im a noob to this stuff.
    Tags: None
    • Van Westervelt
      R3V OG
      • May 2006
      • 9365
      #2
      how is he going to test for compression without spinning the crank? which then moves the pistons up and down, and you want him to do this with no oil in it? ok :)

      If they cant test it, and they dont offer warranty, keep looking.
      sigpic

        Comment

        • So Live
          R3VLimited
          • Aug 2006
          • 2512
          #3
          I agree w/ groupie. I bought a motor w/o testing it and with no warranty and turns out the cylinder head was cracked...
          -Chris

            Comment

            • quillbro
              Grease Monkey
              • May 2006
              • 369
              #4
              ok thanks.

              Upon further investigation into the annuls of R3v and bimmerforms, it turns out you can still do a leakdown test after the motor has been pulled?

                Comment

                • Mossman
                  E30 Mastermind
                  • Apr 2006
                  • 1961
                  #5
                  Yep leakdown you don't spin the motor, you put the cyl. either til the piston is all the way up or all the way down so the valves are both closed, pump XXX psi into it, see how much is there, divide to find difference. Don't expect perfect leakdown on a cold motor that hasn't been run in god knows how long though, which is good news for you. As long as all cyls are consistant motor is probably fine.

                    Comment

                    • 1fastcosmo
                      Advanced Member
                      • Apr 2008
                      • 139
                      #6
                      you could spin the engine with no oil to do the test all though i wouldnt suggest it.THis isnt a auto 99 white vert is it?

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