Haynes manual Torque Specs ARE WAYYY WRONG!!!! - PeachParts Mercedes-Benz Forum

npretnar · #1 07-13-2012, 07:45 PM

The Haynes Manual for the Mercedes Diesels from 1977-1985 says that the torque for the oil pan bolts is 30 FOOT-POUNDS! This is obviously way too high, but I didn't know that the first time I attempted to apply torque, broke off a bolt head, drilled it out, retapped etc. Thought the bolt itself was bad, realizing now that there is no way those little brass bolts can handle that much torque.

Just a heads up to everyone. I believe the legitimate torque is 6-8 ft/lbs. Can anyone confirm this for me?

qwerty · #2 07-13-2012, 07:55 PM

Quote:

Originally Posted by npretnar

Thought the bolt itself was bad, realizing now that there is no way those little brass bolts can handle that much torque.

The correct screws are steel, not brass. The "brass" appearance is due to a corrosion-resistant coating.

M6 oil pan screw torque is 9-11 Nm. M8 is 20-25 Nm. (Per the 617.95 Engine Manual.)

vstech · #3 07-13-2012, 07:55 PM

Hmm. I did not notice this. I'll go verify.

generally, oil pan bolts are of the 30 inch pounds spec...

qwerty · #4 07-13-2012, 08:00 PM

Quote:

Originally Posted by vstech

generally, oil pan bolts are of the 30 inch pounds spec...

Not if you want you oil to stay in the pan, it isn't.

vstech · #5 07-13-2012, 08:03 PM

Hmm
my FSM states 13NM anybody have a conversion on that...

vstech · #6 07-13-2012, 08:06 PM

wow, 115.6 inch pounds...
chevy trans bolts are 70inch lbs, and a thicker bolt... must not be as high a quality fastener!

vstech · #7 07-13-2012, 08:07 PM

wait, that's the spec for pan to crancase bolts... is that what bolt you are torquing? or the lower steel pan?

vstech · #8 07-13-2012, 08:24 PM

Quote:

Originally Posted by qwerty

Not if you want you oil to stay in the pan, it isn't.

obviously, I should have said "more like 30 inch lbs"

still... the oil will stay in the pan longer with bolts torqued to 30 inch lbs than 30 FOOT lbs!

Brian Carlton · #9 07-13-2012, 09:44 PM

Quote:

Originally Posted by vstech

obviously, I should have said "more like 30 inch lbs"

still... the oil will stay in the pan longer with bolts torqued to 30 inch lbs than 30 FOOT lbs!

You're a bit confused regarding the reasons for the torque spec. The screws can handle quite a bit more torque than the specification indicated. An M6 will yield at about 192 in-lb. An M8 will yield at over 300 in-lb.

However, if you tightened them to these levels, the pan, being made of sheet metal, would severely deform due to the point loads underneath the heads of the fasteners.

The trick is to use just enough force to keep the gasket sealed...........and not a single pound more.

compress ignite · #10 07-14-2012, 04:27 AM

You're using the Haines (YES,I can spell,thank you) Manual
for anything other than Amusement...You're asking for trouble!

The Haines "Book of Falsehoods" has screwed more than an Army's collection
of Wrenches out of Beaucoup de Bucks!

Stretch · #11 07-14-2012, 05:07 AM

I've been trying to publicise this for some time - some parts of the Haynes manual are nothing more than emergency toilet paper in my opinion.

To the best of my knowledge most of the values in Nm are more or less in agreement with the FSM - I think I've come across a few that don't. The biggest problem with Haynes is that they can't convert to ft-lbs some of the time...

As a general quick check I think it is best to ask yourself if the value given in ft-lbs is approximately TWO THIRDS of the value given in Nm.

SD Blue · #12 07-14-2012, 10:44 AM

It is necessary to look a little closer at the torque spec's. and realize there needs to be a clarification for "oil pan" as there is an upper and lower.

Haynes Manual pg. 58 Mercedes-Benz Diesel 123 Series 1976-1985

Oil pan bolt
10mm 30 Ft-lbs
12mm 52 Ft-lbs
[NOTE: the size of bolt mentioned.] This is referring to the Upper Oil Pan.

Haynes Manual pg. 85

Torque Specifications
Lower oil pan-to-upper pan bolt 7 Ft-lbs.

It is best to start with generic torque specifications and work from there........

M-6.....6-9 Ft-lbs........9-12 Nm/m
M-8.....14-21..............19-28
M-10....28-40.............38-54
M-12....50-71.............68-96
M-14....80-140...........109-154

I agree that there are a few things "out of order" as to where certain torque listings are made. This is due to their confusion with upper/lower oil pan listings. So you have to watch the size of bolt listed. That is why it better to start with the general torque ranges first.

compress ignite · #13 07-14-2012, 07:18 PM

Not limited to Mercedes chassis!

Every chassis they deal with has these mistakes!

Jerry_W · #14 07-15-2012, 12:13 AM

Slighty OT, but one of my huge complaints against Haynes is the all-to-common "...complicated assembly requiring specialized tools...repairs should be referred to shop or dealer." (Slightly paraphrased.)
If I wanted someone else to do it, I WOULD NOT HAVE BOUGHT A MANUAL!!

The Gears · #15 07-15-2012, 01:08 AM

For the M12 bolt that holds the axle into the rear hub MB sm says 30nm
I think that converts to 22.13 ft/lbs. No way will that long thin bolt take that torque. Or did I read it wrong?