odd problem R12 - bolts shearing
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  1. #1
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    Default odd problem R12 - bolts shearing

    Was pulling down the R12 in prep for the Gero to the Rock Adventure.

    The motor came apart easily, infact some of the bolts were probably not done up tight enough.

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    Am going to get the valves reseated so was stripping down the head. The waterpump came off in seconds and the threads were all good. Then came the temperature sender housing. All six bolts sheared off with no effort whatsoever. Barely got the spanner on them when, "pop" one after another.

    The bolt heads look like they're stainless steel. Is there any issue with using stainless steel bolts in an aluminium head/block?

    Will get the machine shop to demolish the housing plate and remove the bolts as best they can

    P
    Daily Drivers: R10, R12, R17T(?) Decouvrable

    In the Shed(s):
    R8 (1.4 motor, 4 shock rear end), Dauphine, Pugeot 404

    In the Past:
    Dauphine X2, R10 X lots, R12 X2, R16TS, R17TS

  2. #2
    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by Exfrogger View Post
    Was pulling down the R12 in prep for the Gero to the Rock Adventure.

    The motor came apart easily, infact some of the bolts were probably not done up tight enough.

    Am going to get the valves reseated so was stripping down the head. The waterpump came off in seconds and the threads were all good. Then came the temperature sender housing. All six bolts sheared off with no effort whatsoever. Barely got the spanner on them when, "pop" one after another.

    The bolt heads look like they're stainless steel. Is there any issue with using stainless steel bolts in an aluminium head/block?

    Will get the machine shop to demolish the housing plate and remove the bolts as best they can

    P
    As long as the metals came from different pours, there will always be issues.
    SS will cause a greater reaction than plain steel.
    There is a heap of cheap chinese SS hardwear being imported, so I suspect bolt quality has more to do with it than the fact that it is stainless steel.

    I dont know if I'm imagining it, but I think when the motor sits idle for a period, these types of issues are worse.
    Maybe the continual heat cycle has something to do with not allowing a good electrical current to flow..

    I had a brass coolant sensor snap off in the housing this week.
    Threw it into the too hard basket and drove it down to my engine guy who commented that it was a "prick of a job to remove". $20 well spent after hearing him say that.


    Jo

  3. #3
    1000+ Posts schlitzaugen's Avatar
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    That is a common problem with those bolts, Exfrogger. Be happy you didn't shear any of the water pump bolts.

    My approach is to use a generous coating of mild (purple, 222) loctite completely covering these bolts. That's not going to make them hard to remove, but it will keep the water out. Not sure how water goes in there, but it does. make sure the gasket is sealing perfectly too and the problem should be mitigated.

    Another fix to seal the threads I use in BMW M10 engine heads is to silicone the exhaust studs (because they protrude in the head top oil chamber and oil leaks down the threads). Perhaps this can work too. This does not make it difficult to remove the studs later.
    ACHTUNG ALLES LOOKENPEEPERS

    Das computermachine is nicht fur gefingerpoken und mittengrabben. Ist easy schnappen der springenwerk, blowenfusen und poppencorken mit spitssparken. Ist nicht fur gewerken bei das dummkopfen. Das rubbernecken sightseeren keepen hands in das pockets-relaxen und watch das blinkenlights.

  4. #4
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    Thanks for that, Rob.

    Car's been a daily driver. Motor had been rebuilt shortly before I got it, so bad steel might be the issue.

    As I come to think about it. The housing mounts the coil and was being used as the battery -ve connection to the block because the PO had bought battery with the terminals around the wrong way. This meant the earth cable would not attach to the block where it should.

    Ah ha! ... now it all makes sense now! The plate itself sits on a gasket which means the entire current was running thru the shafts of those 6 x 6mm bolts.

    Bugger

    P
    Daily Drivers: R10, R12, R17T(?) Decouvrable

    In the Shed(s):
    R8 (1.4 motor, 4 shock rear end), Dauphine, Pugeot 404

    In the Past:
    Dauphine X2, R10 X lots, R12 X2, R16TS, R17TS

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