Hi there, I was wondering if any one may be able to help me with some info.
I work for a company in the U.K. that has recently won a contract to repair approximately 250 Mercedes OM603.950 engines that have been fitted into a modified off road vehicle.

I work in the workshop and it has recently come to my attention that our engines have 2 types of Crank Bolt and washer fitted.

Some engines have an 8.8 bolt and 3 disc spring washers fitted, others have a 10.9 bolt and a single (10mm approx) washer fitted, and we have seen combinations of the two. These engines were refurbished by a previous company.

I'm trying to ascertain which is the correct/best combination to use as I believe it is well known for the Harmonic Balancer to have a habit of falling off, indeed we have seen several already that have damaged crankshafts due to the front crank pulley having come loose.

From my research on this excellent forum I see that this subject has been discussed several times, but I can't find a definitive answer.

From my research I have seen a torque setting of 200Nm + 90 degrees for the 8.8 bolt with 3 disc spring washers in an online Mercedes workshop manual. I tried this torque procedure today and was surprised by how much effort (and a long bar) is required to achieve the + 90 degrees. That bolt is TIGHT ! Possibly too tight ?

The torque setting of 320Nm for the 10.9 bolt and thick single washer is waayyyyy easier to achieve and is the procedure we have been using up until I started looking into the differences of the 8.8 bolt and 10.9 bolt.

Is the 200Nm +90 degrees with an 8.8 bolt and 3 Disc Springs (Bellville Washers) the recommended advice or is there a new procedure?

Do Mercedes recommend replacing the 18mm bolt each time ?

These engines having been out of production for so long make finding information difficult, or am I not looking in the right place ?

I appreciate any help you could give.

Thanks Fred.