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  1. #1
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    Broken Timing Chain

    OK I have read allot of posts here. Still not sure of answer. Bought an e34 93 m50 525i. Got it for a good price but not running. CHecked allot of things thinking a dumb sensor, NO. After checking spark and fuel( by lifting injector bar and causing a wonderful explosive fire on the block, put it out quickly no damage). Got that. Did compression check . 125 cylinder toward radiator. zero on 2nd 3rd 4rth, 5 had 50 psi and 6th zero. thought head gasket or ??? so decided to check with ghetto leakdown test by potting air in cylinders and listening for air in usual places. well on my way to getting to the cams and removing leaky valvecover.bingo broken timing chain. engine has cranked over with no odd noises. what would i have to check before just replacing time chain. what could all be damaged? still plan on doing leak down to see if valves are holding but andy other things to be made aware of? Thanks for reading all this. its a nice car great interior and love to get it running sweetly. Ed


  2. #2
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    Re: Broken Timing Chain

    If you have a broken timing chain some valves would be bent. Get another engine. I can seel one from a 95 M50tu sitting in my garage cheap.
    AIM: yaofeng4249
    '95 525i 5 speed built 5/94 w/93 m50tu engine
    '94 540it built 3/93, converted to 6 speed w/a '93 e32 M60, 4.0L Nikasil engine
    '01 540it, built 6/01
    '03 325i 5 speed, built 9/02

  3. #3
    floydr
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    valves COULD be bent

    BMW engines are interference engines, so one or more valves could (not an absolute as yaofeng implies) be bent, or pistons damaged. However, damage is likely. Two ways: pull the head, or put a new chain gears and idler on and try it out. I suppose you could remove the plugs and use a scope, too.

    A broken timing chain is very unusual; however broken timing belts on the M20 (M50 predecessor) were a notable cause of broken engines in the '80s and were almost entirely due to poor maintenance.

  4. #4
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    Re: valves COULD be bent

    I just don't see how it is possible to avoid bent valves in this case. At the instant when the chain breaks it is possible there are no bent valves. After the owner scratching his head not getting the car to start cranking the daylight out of the engine do you still think there will be no bent valves? Explain to me your reasoning.
    AIM: yaofeng4249
    '95 525i 5 speed built 5/94 w/93 m50tu engine
    '94 540it built 3/93, converted to 6 speed w/a '93 e32 M60, 4.0L Nikasil engine
    '01 540it, built 6/01
    '03 325i 5 speed, built 9/02

  5. #5
    floydr
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    Lot of difference between certainty vs probability

    Revs, auto vs. manual, lift, clutched vs. engaged, backfire (that slows/stops the engine), did they try a re-start?, randomness.

    If you read carefully, I do use the word: "likely". But that's far different from the terms you used.

  6. #6
    floydr
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    And it might be repairable, too

    Story in this month's Roundel about a guy repairing his E28 M5's engine - 4 bent/burned valves, broken piston. Very similar to the probably damage in a camshaft chain break.

    Don't throw it away until it's checked out.

  7. #7
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    Re: And it might be repairable, too

    You are dancing around answering the question. What has Revs, auto vs. manual, lift, clutched vs. engaged, backfire (that slows/stops the engine), has to do with the fact he said "the engine cranked over"? It means he cranked the engine repeatedly before testing led him to find out the timing chain was broken. What does that tell you on top of the fact it has "ZERO" compression in the 2nd, 3rd, 4th and the 6th hole?

    Even if it has all piston punctured and all valve bent it can be repaired. But at what cost?
    AIM: yaofeng4249
    '95 525i 5 speed built 5/94 w/93 m50tu engine
    '94 540it built 3/93, converted to 6 speed w/a '93 e32 M60, 4.0L Nikasil engine
    '01 540it, built 6/01
    '03 325i 5 speed, built 9/02

  8. #8
    floydr
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    A rebuilt head costs around $1500

    Still a lot less than a $5000+ engine.

    I've rebuilt BMW sixes. Have you? Then I contend that I know more about the subject than you and you need to back off a bit.

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    Re: A rebuilt head costs around $1500

    only 2 bent valves . all pistons scored on top but no visable holes. if i do gaskets will it hold for a while or blow through piston tops? Any suggestions. I can buy 1 of 3 engines I have found with about the same mileage and swap but to do all that,then to me its not a manual wagon which is what i wanted to start with. I would have 1500 into it and then try to sell or use for a while! any suggestions. Ed

  10. #10
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    Re: A rebuilt head costs around $1500

    I am not here to brag about my BMW engine rebuilding experience. So there is nothing to back off. You can have all the engine rebuilding experience all you want but I am correct on this. LOL.
    AIM: yaofeng4249
    '95 525i 5 speed built 5/94 w/93 m50tu engine
    '94 540it built 3/93, converted to 6 speed w/a '93 e32 M60, 4.0L Nikasil engine
    '01 540it, built 6/01
    '03 325i 5 speed, built 9/02

  11. #11
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    Shamelessly marketing my engine..

    Want to buy a 95 M50tu which has been sitting in my garage for a couple of years for a fraction of the cost you mentioned?
    AIM: yaofeng4249
    '95 525i 5 speed built 5/94 w/93 m50tu engine
    '94 540it built 3/93, converted to 6 speed w/a '93 e32 M60, 4.0L Nikasil engine
    '01 540it, built 6/01
    '03 325i 5 speed, built 9/02

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