awww crap did i drop my thrust washer into the engine?!

Discussion in 'Airheads' started by coyotejoe, Oct 4, 2010.

  1. coyotejoe

    coyotejoe Adventurer

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    hey guys!

    my name is joe and im new to this forum and wanted to say hi. ive been lurking on here for a few weeks now while getting some useful information on rear main seal replacements. anyways, i started the project today on my 1976 r75/6 and needed some advice from people who have done this before.

    before i begin i wanted to note that i was following this procedure:

    http://personalpages.tds.net/~nsgreear/bikes/bmw/clutch/Rear_Main_Seal_Nick.pdf

    everything went fine until i hit step 5 on page 6 where it says:

    5. Remove the flywheel brake and remove the crankshaft “stop” at the front of the engine and make sure the crank turns easily. If not, the rear crankshaft thrust washer may have fallen of its pin and is now crushed. If true, tear the engine apart and start over!!!!!

    i noticed that wasnt the case for me. after i tightened down the flywheel bolts it didnt want to budge in either direction. however, when the flywheel bolts arent tightened it can move back and forth. now keep in mind that i definitely blocked the crankshaft using a tool that i bought from jeff trapp and also screwed down the front cover ontop of it so i dont see how the thrust washer could have fallen into the engine.

    is this normal because im kinda freaking out because i just read an article that says:

    If you do NOT block the crankshaft, you run the risk of the crankshaft moving forward a small amount... probably it could possibly move a bit under 1/4", and the HIDDEN thrust washer COULD move off its pegs.If that happens, the thrust washer will not align back on those pegs as you tighten the flywheel bolts, and you run the risk of MAJOR DAMAGE to the thrust washer....AND even the engine casting! You will find that the crankshaft will essentially nearly freeze up as you tighten those bolts.

    any advice would be greatly appreciated
    #1
  2. P B G

    P B G Long timer

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    So... you didn't block the crank?

    Oh wait you did...

    Hmm.
    #2
  3. coyotejoe

    coyotejoe Adventurer

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    one thing i forgot to mention was that after i took off the flywheel i started cleaning the inside of the casing and noticed that there were some gear teeth on the topside of the casing that i think turn the flywheel? i didnt notice them after i pulled the flywheel out but noticed that something was spinning as i was cleaning it. does anyone know what that does and if that will affect my situation?

    i know timing is critical because there were alot of steps that said make sure everything is still top dead center
    #3
  4. TimTowtdi

    TimTowtdi Been here awhile

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    How far did you press the rear main seal in? If you used one of the tools with the three little set screws to set the seal depth, you need to make sure they were at the lowest setting, so they stuck out the least amount according to the instructions. Like one turn or something. If you leave the seal sticking too far out, it will rub on the flywheel and make it not be able to turn. DAMHIK.
    #4
  5. TimTowtdi

    TimTowtdi Been here awhile

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    That is the starter. Don;t worry about it. If they turn that is good.
    #5
  6. coyotejoe

    coyotejoe Adventurer

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    i bought the tool from jeff trapp as well and i just screwed it all the way in until it was pretty much flush. ill try removing the flywheel and put the tool back on to push the seal in some more.
    #6
  7. bmwrench

    bmwrench Long timer

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    It's possible to dislodge the rear thrust washer, too. Make sure it's still on the pins.
    #7
  8. Hawk Medicine

    Hawk Medicine Coyote's Brother

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    I had one of the local mechanics here in Santa Rosa do that to my engine and the symptoms sure sound the same... :eek1

    I would suggest that before you go any further, you pull the left jug and take a look at that internal shim to make sure that it's still on the pins. If it isn't ginched, you have dodged a huge bullet but if it is fraakked, you're going to have to pull the crank and replace that shim with a new one of the same thickness.

    And no... I wouldn't even think about trying to start that engine without doing a visual inspection first. :yikes
    #8
  9. datchew

    datchew Don't buy from Brad

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    +1
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  10. mcma111

    mcma111 Long timer

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    I think I read somewhere that you can access the shim by removing the oil pan and getting it from below. Or turn your motor upside down. I had the shim come loose on me last year. I used a piece of coat hanger and inserted it through the dowel that the shim goes onto and when the shim is in the correct position the wire would hit the crank. You could hear it when it hit. It took a while but it was better than pulling the crank.
    #10
  11. ericrat

    ericrat Long timer

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  12. OldAndBusted

    OldAndBusted Needs a little work...

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    i did this. destroyed one of the thrust washer locating pins and of course the washer too. that was fun. took a bit of work to find a new metric solid dowel pin the right size. bmw never sold them as parts, they were just pressed into the engine case.
    #12
  13. elite-less

    elite-less Been here awhile

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    +1

    Also, when you take the flywheel off rub a color dye on the rear main seal. Install the flywheel and then remove it…. transfer of the dye will indicate any contact.

    An incorrect rear main seal depth will make crank rotation difficult.... ask me how I know.
    #13
  14. kixtand

    kixtand Long timer

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    Actually, you need to pull the right cylinder, not left. None the less, that is the first thing I would do after removing the fkywheel and inspecting the seal and such. You should be able access the internal thrust washer w/ the right cylinder and piston removed.
    #14
  15. bmwrench

    bmwrench Long timer

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    Just need to know where to look! 11111250156
    #15
  16. coyotejoe

    coyotejoe Adventurer

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    craaaaaaaaaaaaaaaap. so i removed the flywheel again and pushed the seal in as far as i could and when i tried to spin it, it wouldnt budge at all. i started to think what could have gone wrong and i noticed a piece of metal that came loose as i was pushing around the seals. some how the slinky looking spring circular thing that hides behind the copper plate was crushed and broke.

    im not sure what its purpose is and how it got crushed but im guessing its not good and could partially be a reason why things arent moving the way it should.

    i did torque the flywheel bolts to 75 ft/lbs and noticed a weird sound which was probably the spring being crushed but i have no idea how that could have happened....any suggestions?
    #16
  17. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    Inside the lip of the seal there is a spring that keeps tension on the seal lips. It probably is probably that and it got dislodged when you removed the old seal (or installed the new one, make sure that it isn't from the new seal).

    Without pics, just guessing... :evil
    #17
  18. AntonLargiader

    AntonLargiader Long timer

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    You have an older design seal. Replace it.

    This is good news.. you don't have to pull the crank yet.
    #18
  19. kixtand

    kixtand Long timer

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    I'm assuming that the copper plate you are referring to is the thrust washer that goes twixt the flywheel and the engine case, and the spring you are referring to is the spring that goes around the lip of the rear main seal. Assuming I am correct (I know, a lot of assumptions ...) it sounds like the spring became dislodged and somehow got under the thrust washer. So, based on that, I would closely inspect the thrust washer to make sure there is no damage. If there is, replace the thrust washer, which means checking the crank endplay, at a minimum.
    #19
  20. coyotejoe

    coyotejoe Adventurer

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    i took some pictures last night but for some reason i cant upload them...anyone know why?

    so after reading Bill Harris' and AntonLargiader's response it sounds like the spring they're referring to is the same one. it keeps tension on the seal lips. my new seal didnt come with one...is it supposed to?

    now the copper plate that it sits behind, is that the thrust washer?

    and what is the crank endplay?
    #20