1986 190E 2.3-16 Head Bolt Torque Question

[JimSmith]

Well, the head is back together and located on the block, with the bolts all finger tight. I went to look at my manuals to find out the tightening procedure and the official MB manual I have gives a torque value of:

"Torque specifications and tightening diagram for cylinder head bolts are identical to the other engines 102"

This is a manual that has the 2.3-16 valve engine "differenced only" described. So, I bought a Haynes manual for the basic 2.3 liter engine, which includes various paragraphs and hints where a 2.3-16 valve engine is different, too. For the head bolts and the four 6mm Allen head sockets this manual says:

"M12 Cylinder head retaining bolts
Stage 1................52 ft.-lbs.
Stage 2................Tighten further by 90 degrees
Stage 3................Tighten further by 90 degrees"

and,

"Cylinder head front bolts (M8)..........18 ft.-lbs."

The detailed instructions say, do the M12 cylinder head retaining bolts first, all the way through "stage 3" and then install and tighten the front M8 bolts.

Now, the last bit of data I got from this path turned out to be drastically in error and I was lucky enough that M.B.Doc checked what I posted and provided correct data to me. If anyone has this information available to them and can confirm what the correct cylinder head tightening values and sequences are for these fasteners, I would greatly appreciate the help. Thanks, Jim

[Gilly]

I show 55nm, then 90 degrees and another 90 degrees, again you do these in stages, tighten them to 55nm in the shown sequence (I assume you have the sequence), then turn them all 90 degrees in the same sequence, and then again 90 degrees in that sequence. I show the front hex bolts at 25nm, I assume these are done at any time, I'd do them right after the big bolts are tightened to 55nm, then recheck after each angle torquing is done.
edit: recheck front bolts after each SERIES of tightening is done, not every bolt

Gilly

[engatwork]

I assume you have the sequence

It is in the Haynes manual.

Did you have to replace any of the large cyl head bolts because they were below spec?

As Jim indicated, you should measure the bolts to make sure they are not already stretched beyond spec. They are usually good for a couple of additional torquings after the first one at the factory.

Either make paint marks on all the bolts before you start, or make SURE that you are not interrupted during the sequence and lose your place. Also get ready for a workout and get ready for the fact that you will think that you are going to break the bolts. Don't use a torque wrench for the 90 degree sequencing, you will ruin it. Get a good quality breakover bar.

Good luck,

[JimSmith]

Well, I got it all together, all the timing matchmarks lined up. I even put a white dot of "white out" on the chain and the sprockets to make sure everything was all lined up correctly. Then, before putting the valve cover on, I decided to turn the engine by hand. I forgot to put the chain tensioner on and I skipped a link or two. So, out come the camshafts and now I am trying to make sure I have top dead center again. How do you read the timing marks on this engine? The manuals I have are not exactly clear, or the engine is a little greasy and dirty because I can see a plug in the balancing ring, but no timing marks.

I could kick myself. It was nearly done! Just put the chain tensioner in and I was finished with that part. I still have the radiator out (waiting for a new one) and have a few other odds and ends to complete, like getting the manifolds on again and restoring all the junk we took off and likely broke, as well as decoding the wiring and vacuum hoses.

The head bolts were checked by the machine shop and pronounced good. So I reused them. Jim

[JimSmith]

Larry,

I used a big torque wrench and set it to 180 ft.-lbs. It never clicked. On the second set of turns I set it to 150 ft.-lbs. and again it never clicked. Went quite smoothly, and yes, I did think I might twist off the heads of the bolts. This is first time the head has been off (the cylinder head height was per the new head specs for height). Other than some carbon crap inside the engine, and a ring of black stuff at the top of each cylinder, the bore of the cylinders was great. All the original honing marks were visible. Jim