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-   -   why does the crankshaft bolt keep coming out? (http://www.peachparts.com/shopforum/showthread.php?t=6585)

Larry Delor 03-06-2000 08:05 AM

Hello all,

As some may remember, a week and a half ago I had my crankshaft pulley come off-the big 27mm bolt was cracked in two. After fishing out the remaining bolt and getting a replacement dampener and pulley (used) I was pretty sure that all was well. Well it's not! I have no idea why I found the bolt laying on the ground this morning seconds after start up. I am thinking about hiring an exorcist. Any other ideas?
-thank you
-Larry

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03/83 300D
07/73 280



WDurrance 03-06-2000 09:18 AM

Hi Larry,
Was the replacement bolt tightened to spec? The crank bolt should be torqued to 270-330 nm (199-243 lb-ft). If it's torqued that tight, it won't come loose. If the threads are damaged, it won't hold that much force.
Regards,
Randy D.

------------------
W.R.Durrance
ASE Master Tech
Mercedes Tech 20 Years
68 250SE
68 SAAB 96 Ice Racer
69 300SEL 6.3
70 300SEL 3.5
81 300TDT

Larry Delor 03-06-2000 07:07 PM

Thank you for the reply Randy!

I was there when the bolt was tightened, but I do not recall a torque wrench being used, and if it indeed needs to be tightened to around 200ft/lbs, then I would think that a 2-3 foot pipe would have come in handy to reach that spec. (I didn't see that either)

Well things where not ruined as much as the last time, however those two little round cylindrical pieces of steel are (of course) not available from the dealer until tomorrow. I will mention the specified torque, and see if he still wants to go with lock-tite, or a big helper bar to get it to the specified tightness.
ps: they don't do exorcisms on cars, although if this happens again...I might need one. ;)

-Larry

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03/83 300D
07/73 280




[This message has been edited by Larry Delor (edited 03-06-2000).]

JRBrown 03-06-2000 07:14 PM

Food for thought, I had to recently change out the front crank seal on my 110 engine. When the bolt was reinstalled at that very high torque setting, my manaul called for 4 special washers (probably the wrong name) that had a crown to them.

If your application calls for those washers and they weren't used, there might be an additional problem there.

Cheers,

J.R. Brown
1986 280 GE
1980 450SEL
1981 Volvo

Benzmac 03-06-2000 09:02 PM

I do not use a thread locker. I simply torque the bolt with a huge 1/2 in drive torque wrench to 225ft/lb. :eek:

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Benzmac:
1981 280GE SWB
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM




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