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M42 + Water Do Not Mix

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    #16
    Originally posted by AndrewBird View Post
    You probably DID hydrolock the engine and bent a rod. Did the exact same thing in a MK2 Jetta I used to own. Went through a deep puddle, hydrolocked it, got it back running after a oil change, then 2 weeks later it blew TWO holes in the block.

    For future reference, running the engine AT ALL with water in the cylinders will damage it. Also, if it has been run after getting water in, there won't be any more later. If there is, it means you have a blown head gasket and coolant is getting into the cylinders. The combustion process will vaporize any small amount of water and it will go out the tailpipe.
    Crazy. This is what I concluded too. It was just enough water to do damage in the head.

    It seems you are basically screwed either way. Either let you engine die with a ton of water in it or keep it running at low RPM to mitigate the amount of water in there.

    I have sure learned my lesson about plowing into a deep puddle with a volvo lip at 45mph.

    1991 318iS Sterlingsilber - 1989 325i Cirrusblau (sold) - 1990 318iC Brilliantrot (sold)

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      #17
      interesting. i wonder how deep that puddle was. my m42 drove through this and was fine (actually the crank position sensor took on lots of water so I had a minor misfire for a day). but this wasn't the worst water i've driven through, i've actually had water up to the headlights, which was on accident. no misfire from that though.

      Originally posted by TSI
      ♫ Rust flecks are falling on my head...♫
      OEM+

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        #18
        Hey, wait, you turned, unacceptable.

        I would think that you'd need water to pool in the airbox in order to get a hydrolocked engine. Otherwise vapor, or a few tablespoons here and there shouldn't cause the engine to go kablooie. Otherwise you'd just need to get unlucky with a wave or two.

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          #19
          Originally posted by lolcantturn View Post
          interesting. i wonder how deep that puddle was. my m42 drove through this and was fine (actually the crank position sensor took on lots of water so I had a minor misfire for a day). but this wasn't the worst water i've driven through, i've actually had water up to the headlights, which was on accident. no misfire from that though.

          Balls to the wall.

          Yeah if you notice in your vid it appears very little water went near the intake.

          There was a giant pick up next to me in traffic that actually sprayed water on the drivers front side of the car. I don't blame that though because I was still going too fast.

          1991 318iS Sterlingsilber - 1989 325i Cirrusblau (sold) - 1990 318iC Brilliantrot (sold)

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            #20
            I would think that you'd need water to pool in the airbox in order to get a hydrolocked engine
            This. And there's a tiny little drain hole in the airbox... So if you can SEE water coming
            and not avoid it, clutch in and switch off. Or as soon as you can, get down to idle,
            just to minimize the chance of sucking water in through the airbox.

            Because the filter will hold it off for a split second, then it'll dribble down through,
            filling the airbox and then getting up to where the engine can suck it in quantity.
            At low revs, this will take time.
            At redline, it's "SplashBAM!"

            It's pretty hard to get enough water into the intake to hydrolock- UNTIL the
            intake goes underwater. Then you're doomed.

            t
            now, sometimes I just mess with people. It's more entertaining that way. george graves

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              #21
              What about building enough speed, then go through at 0 throttle, and wait for drainage on the other side of the puddle? Not safe for a multitude of reasons, but good for the engine?

              Throttle closed seems the most important aspect as I don't believe the ICV can pass enough water to kill the engine.

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                #22
                Originally posted by roguetoaster View Post
                What about building enough speed, then go through at 0 throttle, and wait for drainage on the other side of the puddle? Not safe for a multitude of reasons, but good for the engine?

                Throttle closed seems the most important aspect as I don't believe the ICV can pass enough water to kill the engine.
                Shut it down and roll through, it can't pull in water if its not running.
                -Christian

                '02 ///M3 CarbonSchwartz 6MT daily beast
                08/91 Mtechnic II 325IC alpine/lotus
                318iS, slow build/garage queen...
                '37 Chevy pickup, the über project
                Originally posted by roguetoaster
                Be sure to remind them that the M42 is one of the best engines ever made, but be sure to not mention where it actually falls on that list.

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                  #23
                  Originally posted by SSE30 View Post
                  Either let you engine die with a ton of water in it or keep it running at low RPM to mitigate the amount of water in there.
                  You don't seem to understand. If there is enough water in the engine to hydrolock, running at ANY RPM will cause damage. Same space and same amount of water regardless of RPM. You could turn it over by hand and damage it.

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                    #24
                    Originally posted by AndrewBird View Post
                    You don't seem to understand. If there is enough water in the engine to hydrolock, running at ANY RPM will cause damage. Same space and same amount of water regardless of RPM. You could turn it over by hand and damage it.
                    Well, I certainly understand now. I learned the hard way. lol. Next time I'll shut it off immediately and tow it.

                    1991 318iS Sterlingsilber - 1989 325i Cirrusblau (sold) - 1990 318iC Brilliantrot (sold)

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