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The Mechanics Quiz

  • 09-07-2009 11:15PM
    #1
    Slidey
    Closed Accounts Posts: 12,811 ✭✭✭✭


    Right today I saw something quite strange and it baffled me.

    It wasnt me working on the vehicle but I was asked my advice and my 2 guesses were wrong... way wrong.

    So what i want to see is do the smart guys of the Motors forum have the answer.

    2007 Mercedes Sprinter Ambulance.

    Standard CDI engine, 4cyl ~ 150bhp, Automatic gearbox.

    Towed into the garage after another guy had had a look at it. It would turn anti-clockwise but would not turn clockwise. Would just lock solid. Could turn in the opposite direction with no undue effects or noised to be heard.

    Logical reasoning please and I will give the answer tomorrow. ;)


Comments

  • #2
    DaMonk
    Closed Accounts Posts: 200 ✭✭DaMonk


    Slidey wrote: »
    Right today I saw something quite strange and it baffled me.

    It wasnt me working on the vehicle but I was asked my advice and my 2 guesses were wrong... way wrong.

    So what i want to see is do the smart guys of the Motors forum have the answer.

    2007 Mercedes Sprinter Ambulance.

    Standard CDI engine, 4cyl ~ 150bhp, Automatic gearbox.

    Towed into the garage after another guy had had a look at it. It would turn anti-clockwise but would not turn clockwise. Would just lock solid. Could turn in the opposite direction with no undue effects or noised to be heard.

    Logical reasoning please and I will give the answer tomorrow. ;)
    The steering would turn anti-clockwise or the wheels would only rotate anti clockwise?


  • #3
    Slidey
    Closed Accounts Posts: 12,811 ✭✭✭✭Slidey


    Ooops the Engine was what would turn anti clockwise and not in the normal direction


  • #4
    quarryman
    Registered Users, Registered Users 2 Posts: 7,498 ✭✭✭quarryman


    was it in reverse?





    yes that's a joke.


  • #5
    Saab Ed
    Closed Accounts Posts: 5,372 ✭✭✭Saab Ed


    Slidey wrote: »
    Ooops the Engine was what would turn anti clockwise and not in the normal direction


    I remember this happening with a 2 stroke motorbike years ago. The timing was just off and if you caught the piston near TDC and it fired the crank would fire backwards. It was very funny actually to see a motobike with 5 reverse gears :D This was an old Bultaco I saw this happen to. Is it anything similar. Can you map it to fire at the right wrong time ....if you know what I mean?


  • #6
    Slidey
    Closed Accounts Posts: 12,811 ✭✭✭✭Slidey


    No thats not it.

    You could put a bar and socket on the crank pulley and absolutely no budge forward but free to move back ward as much as you want, at any stage of the revolution trying to move it forward resulted in engine lock.


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  • #7
    mickdw
    Registered Users, Registered Users 2 Posts: 23,999 ✭✭✭✭mickdw


    Blocked exhaust?
    Im not a mechanic at all so I may be very wrong


  • #8
    Slidey
    Closed Accounts Posts: 12,811 ✭✭✭✭Slidey


    Nice guess but no matter how blocked it could get there would be a stage of compression which would give you some travel CW.


  • #9
    Saab Ed
    Closed Accounts Posts: 5,372 ✭✭✭Saab Ed


    OK then , Im susspecting the problem is in the box and not the engine. Is that correct?


  • #10
    Fishtits
    Closed Accounts Posts: 1,382 ✭✭✭Fishtits


    30 sec thoughts:

    Assuming the trans is off line.

    There's a one way clutch somewhere that's facilitating movement of a seized component in the opposite direction...

    Alternator seized?


  • #11
    Slidey
    Closed Accounts Posts: 12,811 ✭✭✭✭Slidey


    Saab Ed wrote: »
    OK then , Im susspecting the problem is in the box and not the engine. Is that correct?
    That was my thoughts.

    Yer man that was at it took the bolts out of the torque converter to see if it made a difference.
    Fishtits wrote: »
    30 sec thoughts:

    Assuming the trans is off line.

    There's a one way clutch somewhere that's facilitating movement of a seized component in the opposite direction...

    Alternator seized?
    Bingo!

    Maybe I am a bit slow but wouldnt have thought of this. I was sure the fan belt would just slip.

    Anyway, you win, congrats!


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  • #12
    quarryman
    Registered Users, Registered Users 2 Posts: 7,498 ✭✭✭quarryman


    Can someone explain this in laymans terms? I'm not following.


  • #13
    Slidey
    Closed Accounts Posts: 12,811 ✭✭✭✭Slidey


    There is a one way clutch on the pulley of some modern alternators.

    The pulley was free to rotate back the way when engine spun Anti CW, but would lock up when turned CW


  • #14
    Fishtits
    Closed Accounts Posts: 1,382 ✭✭✭Fishtits


    My prize? Kylie or similar per chance?

    Nah, thought not... :(


  • #15
    Saab Ed
    Closed Accounts Posts: 5,372 ✭✭✭Saab Ed


    Good man Fishtits


  • #16
    peasant
    Registered Users, Registered Users 2 Posts: 17,789 ✭✭✭✭peasant


    Ok ...so that's what happens when you try to turn over the engine by hand.

    But surely the engine would run normally, seized alternator or not, albeit accompanied by an awful belt screeching sound? Or can a seized alternator stop an engine from running altogether?


  • #17
    Slidey
    Closed Accounts Posts: 12,811 ✭✭✭✭Slidey


    Turning the engine over by hand was a no go.

    The engine wouldnt turn by the starter either.

    I was surprised more by the fact that the belt was not slipping than the fact the alternator just seized solid.


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