I have a 91 e300 te M103 gas engine and need the torque sequence for the head and what is the newton meters for the head bolts? Thank you in advance. George

This is from the W126 manual CD. Same engine.

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1989 300 SEL that mostly works, but needs TLC

You need to either check your existing head bolts to ensure that they are within tolerance, or better yet, replace them altogether. (The new bolts have a built in washer.)

These bolts are 'torque to yield', and thus get stressed into the plastic region of the stress / strain curve, which work hardens them. I was very nervous during the last 90 degree torque sequence on my head, and that was with new bolts installed.

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On the plains of hesitation bleach the bones of countless millions who at the dawn of victory, sat down to wait, and waiting -- died

http://mb.braingears.com/

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

There was some discussion way back when about the W126 manual saying 70 Nm and the W124 manual saying 55 Nm. I don't know if Gilly ever came to a conclusion.

I agree that a 300E and 300SE have the same basic engine so I don't know why the manuals have different specs.

Sixto
95 S420
87 300SDL

It really won't matter if it is 55 or 70 as long as they are all the same IN SEQUENCE before the angle torquing. It is the angle torquing that is the important part. You have to be prepared to feel like you're going to break them in half. You also need to go through the sequence without interruption so you don't lose your place. Also be prepared for a workout.

Good luck,

I will utilize the spec 55nm for my vechicle. I see the sequence and want to know if after the initial sequence all new head bolts should be at 55nm and then after that I do not understand 90degree rotation what does this mean and this is done a second time? Clarification would be helpful here. Thank you George

OK, here goes

There are 3 iterations of torquing you do.

1st iteration: Following the sequence laid out in the diagram for the 14 head bolts, you torque them to 55 N*m (about 41 lb*ft).

2nd iteration: Starting over at Bolt #1, you goe through the torque sequence again, only this time don't use a torque wrench. Switch over to a breaker bar so you don't damage your torque wrench, or else set your torque wrench as high as it goes. You then tighten each bolt in sequence with a 90 degree rotation. No torque measured, just tighten the bolt 90 degrees, or 1/4 turn.

3rd iteration: Start over at Bolt#1 and repeat, tightening all 14 bolts again, in the proper sequence, another 1/4 turn or 90 degrees. Then you are done.

This is what I mean by 'torque to yield' bolts, or also called angle torquing. You are actually going beyond the elastic region of the bolt material's stress, into the plastic region. Once you get to the yield point, the torque will actually change very little as the bolt gets stretched. This is why it is important to either replace the bolts, or make damn sure they are within the specified allowable stretch limit before you start.

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On the plains of hesitation bleach the bones of countless millions who at the dawn of victory, sat down to wait, and waiting -- died