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-   -   mercedes engineer - a Godsend, Haynes manual -the devil incarnate (http://www.peachparts.com/shopforum/showthread.php?t=196127)

tangofox007 08-04-2007 09:30 AM

Quote:

Originally Posted by Pequod (Post 1582432)
The Haynes is a reference book.

Quote:

Originally Posted by Pequod (Post 1582432)
Common sense states that the size of that bolt will never support that amount of torque!

The tensile strength of a M12 bolt varies by approx 500% depending on property class (grade.) Depending on the class, 96 ft/lbs is not terribly out of line for that size bolt.

Brian Carlton 08-04-2007 09:36 AM

Quote:

Originally Posted by tangofox007 (Post 1582476)
The tensile strength of a M12 bolt varies by approx 500% depending on property class (grade.) Depending on the class, 96 ft/lbs is not terribly out of line for that size bolt.

Was that an M12 that failed at 96 ft.-lb?

Must have been quite a low grade bolt...........

t walgamuth 08-04-2007 09:43 AM

Quote:

Originally Posted by tangofox007 (Post 1582470)
That does not change the fact that the torque value in question in incorrect in the Haynes publication. There have been a number of reports on this forum of stripped threads in the engine support as a result of overtorquing the mount bolt.



Have you heard the saying "Good judgement comes from experience. Experience comes from bad judgement?"

I am just trying to point out to use judgment and not follow blindly. I am not trying to bash the hapless fellow who broke the bolt. If I were him I would be upset too.

And I am defending the haynes books which seem to get bashed around here frequently. In my experience they are very good for most things. I do own fsm for several engines though. But for most of the things that I do I can find what I need a lot faster in the haynes book.

Tom W

tangofox007 08-04-2007 09:48 AM

Quote:

Originally Posted by Brian Carlton (Post 1582481)
Was that an M12 that failed at 96 ft.-lb?

I took it to be that bolt, but it's not exactly crystal clear. I may have misunderstood; probably should have used more common sense.

tangofox007 08-04-2007 09:52 AM

Quote:

Originally Posted by t walgamuth (Post 1582486)
And I am defending the haynes books which seem to get bashed around here frequently. In my experience they are very good for most things.

I certainly agree with that. I have never understood why Haynes gets slammed so often.

Brian Carlton 08-04-2007 09:57 AM

Quote:

Originally Posted by tangofox007 (Post 1582491)
I took it to be that bolt, but it's not exactly crystal clear. I may have misunderstood; probably should have used more common sense.

I didn't think it was M12.......??

That's a huge cap screw.........

tangofox007 08-04-2007 11:55 AM

Quote:

Originally Posted by Brian Carlton (Post 1582499)
I didn't think it was M12.......??

That's a huge cap screw.........

The 617.95 manual says that the larger bolt (frame to engine bearer) is M12, smaller two (mount to frame) are M8.

But I'm not sure if I should believe that or just use common sense instead!!!

Brian Carlton 08-04-2007 12:17 PM

Quote:

Originally Posted by tangofox007 (Post 1582575)
The 617.95 manual says that the larger bolt (frame to engine bearer) is M12, smaller two (mount to frame) are M8.

But I'm not sure if I should believe that or just use common sense instead!!!

That's a beefy screw for that location. I'm still surprised it failed at 95 ft-lb. As you noted, must be a grade 3 or less.

lietuviai 08-04-2007 02:43 PM

Quote:

Originally Posted by toomany MBZ (Post 1582428)
The MB service manual does not have any torque specs for the manifold.

That's what I was referring to.


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