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    Bizarre timing belt problem

    I've run into a weird timing belt problem that I can't seem to resolve. Hoping that maybe someone here has run into this before and can shed some light on how to fix it.

    I recently swapped out my turbo m20 for my 3.0l stroker. I got tired of bad gas mileage and an unreliable megasquirt. I got everything back in and running and all seemed well. I took it out, banged through a few gears and then headed back home for the night.

    Then next morning I'm on my way to work and bang through a couple of gears getting on the freeway and I start hearing this HORRIBLE squealing noise. I eventually trace it back to the edge of the timing belt rubbing on the inside of the lower timing cover.

    The timing covers were powdercoated on both the inside and outside. I intially though it was warped form the baking process or was a clearance issue, so I swapped it for a stock unpainted one. Reinstalled, all was fine until I banged through some gears again. Added a couple of washers behind the cover to add clearance, the problem again resurfaced. Added tension to the tensioner and losened it. Problem still exists.

    At this point, I've gone through 3 timing belt tensioners, two timing belts, two sets of timing covers. The problem still resurfaces under hard acceleration. It seems like the belt keeps sliding forward like it's trying to come off the gears. I've had this engine in the car before and never had this issue. When I pulled it, the motor sat on an engine stand for about 2 years before going back in the car.

    HELP?! I'm about to put a bullet in the motor at this point.
    - Jason


    #2
    is something out of alignment along the longitudinal direction so that the belt is out of plane?
    89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

    new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

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      #3
      The timing belt sliding to either the front or back means that the tensioner is bad or that one of the sprockets is out of plane or cocked. Since I can't see the cam or crank sprockets as being off, I'd suspect the intermediate shaft. Bad bearings there could cause this problem.
      The car makes it possible, but the driver makes it happen.
      Jim Levie, Huntsville, AL

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        #4
        Thanks for the reply guys. Much appreciated. Is it possible to replace the intermediate shaft/oil pump gear while the engine is still in the car, or am I looking at a full tear down?

        I reinstalled the tensioner today using only the tension provided by the tensioner spring at Ryan G's recommendation. He's thinking that by over-tightening the tensioner (I've always used light to medium pressure with a pry bar) it's somehow causing the belt to shift under heavy load. I took it out afterwards and ran it pretty hard. So far so good. But time will tell.
        - Jason

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          #5
          Proper tension on the belt is provided by the spring. More tension than that would lead to short belt life and could cause other problems. Insufficient tension would cause other problems. The spring is there for a very good reason. You can replace the intermediate shaft without tearing down the engine. But replacing the bearings is a royal pain and would have to be done on a bare block.
          The car makes it possible, but the driver makes it happen.
          Jim Levie, Huntsville, AL

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            #6
            Thanks again for the info. I'll see how things go over the next few days and will post once I've got some more miles. Hopefully my next post will be a happy one.
            - Jason

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              #7
              digger,

              Just out of curiosity, what are the specs on your m20b31? I'm running at close to 200whp. Wondering what your setup looks like that's getting you 220 to the wheels.

              Thanks :)
              - Jason

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                #8
                Well, I'm now very happy to report back with the results. Adjusting the timing belt tensioner to just the spring-only tension seems to have down the trick. Four days with a lot of hard acceleration and no more noise. Thanks for your input gents. Very much appreciated!!
                - Jason

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