OM617 Timing after Rebuild - Page 3 - PeachParts Mercedes-Benz Forum

mannys9130 · #31 11-25-2015, 09:30 PM

I'd keep everything in order on principle. Use an egg carton for valve components, mark pistons, keep bearing in order ESPECIALLY if reusing.

If you were to polish the crank and use new or plus sized bearings, you wouldn't need to worry about matches. New surfaces haven't met and won't be upset being put with a strange surface.

Kind of like introverted people.

leathermang · #32 11-26-2015, 12:31 AM

Manny's answer is correct...
The rings are designed to wear against the roughened ( crosshatched surface ) so that once worn in they really fit together.

BillGrissom · #33 11-27-2015, 12:42 AM

New rings may be sufficient if you still see the original cross-hatching everywhere in the cylinder. If not, the cylinder may be too worn to just "hone". It may be worn oblong. In gas engines, one then generally bores the cylinders out to the next standard size and buys new pistons and rings. But that is not possible in our engines because there are no over-bore pistons available and even the std size are currently not affordable ($500 each!). For a Chevy small block, you can get a set of 8 pistons for <$100.

But, we can actually do better. The OM617 has cast-iron cylinder liners that can be affordably replaced. I removed mine by just driving a flat screw-driver from the bottom between sleeve and block, which easily rips the cast iron sleeve, then just slide it out. Installing the new ones is harder. I heated the block and chilled the new sleeves, but still needed to rap a sledge hammer on a steel plate above to slide each one down. The sound tells you when they seat on the upper lip. But be careful since they can easily crack. Then, a shop machines the sleeve bores to match each piston. You need them fairly close so you don't get "piston slap", which is common if one just re-rings and the bore is too worn. Of course, all is more critical in a diesel. The result is well-matched pistons and bores, with bores back to original spec.

BTW, unlike gas engines, very few here have rebuilt a diesel and seems very few shops do it, and none affordably that I have read. If you do so, you will be a hero at a young age. One guy here a year or so ago posted similar and seemed a bit naive, but then finished in <1 week and posted photos. They were on a remote ranch, but had machines for decking blocks, honing, and all. Amazing post that you should search for.

mannys9130 · #34 11-27-2015, 03:09 AM

Watch this video.
https://www.youtube.com/watch?app=desktop&persist_app=1&v=iYpzeVNcEG4

Jaffro makes very good educational videos. He shows how you'll be measuring the bores for being out of round. If they're out of spec, replace the liners. New liners, bored and honed to match your pistons, with new rings, and new bearings would be "rebuilt" as far as the bottom end is concerned. If your valve guides are in spec and a lap brings the margins to a good surface in the right spot, just replace the valve stem seals and call it done.

ollo · #35 11-27-2015, 11:32 AM

I'm going to 2nd BillGrissom and encourage you to get on with renovating that engine. I did 2 of them back in the 80's, a 78 300D NA and some years later an 81 300SD. I had prior experience on Ford, Chevy, Chrysler gas engines plus 1 BMW 4 cylinder engine and I had an old Haynes manual with info for the 617 NA engine.

On the 300D, I was fortunate to work with a local machist in Kingston, WA. He had never done a diesel but wanted to try one. I removed, disassembled, re-assembled and
re-installed the engine. It fired right off 1st try, ran trouble free for years thereafter.

The turbodiesel engine wasn't covered by my Haynes, but was similar enough that I got it apart and back together correctly again with help of a local machine shop ("Thumpers") in Olympia, WA. Again, engine fired right off 1st try with no problems, despite my yellow lab puppy retrieving engine parts off my bench and dropping them into my hand throughout the process!

I re-used all the original pistons on the 300D, and 3 of the originals on the 300SD, with 2 used pistons from Potomac German Auto. Back then they charged me for 2 used pistons, but sent 5 good ones so I could choose the best.

Just take your time and think through everything as you go. You can do it. Don

leathermang · #36 11-27-2015, 11:56 AM

It is not whether it ' starts right up' for most people .... if they have invested the money in parts and the time in rebuilding they usually have some expectations of an engine which will give great efficiency and last a LONG time....
THAT is what is at stake in terms of following the very very specific specifications which the factory supplies with the FSM....
' Experience with other brand engines' is often worthless when dealing with our 617 diesels.... and you quickly recognize that if you actually read the FSM instructions.
What often does not get said with ' promoters ' of iffy projects or methods....is that they have NO SKIN IN THE GAME.... it is not the promoters who will be out the money and time they are so ready to encourage others to RISK...

ollo · #37 11-27-2015, 12:46 PM

True enough, but in both cases I ended up with a beautiful Mercedes whose engines had all new cylinder liners, rings, bearings, timing chain, tensioner, guides, & seals. They did run with great efficiency and lasted for a LONG time. The new parts and machine shop time cost some $$ but fell far short of what I would have had to pay for a Benz already in the final condition of my cars. "Starting right up", with none of the problems I sometimes hear of on this site, was just the 1st encouragement of what subsequent years of trouble free use confirmed. Don

leathermang · #38 11-27-2015, 01:00 PM

Ollo, the point is not that you did not do a good job...
but that you do not know the expertise of this OP....or the people he has available to him... so I say caution is advised as compared to unrestrained ' positive attitude' .....

engatwork · #39 11-27-2015, 01:03 PM

I agree, go for it young man and take plenty of pics during disassembly.

ollo · #40 11-27-2015, 01:19 PM

You are right to some extent, but the OP did convey to us that he attends an automotive tech school and has access to their shop equipment, so I took that into consideration.

Previous experience on other engine types does improve your mechanical capability as far as dis and re-assembly and it increases your confidence to attempt more complex and difficult projects.

We were all young and ignorant once, but experience and reason encouraged us to attempt difficult things. Life is good! Don

leathermang · #41 11-27-2015, 01:19 PM

I am not saying ' don't do it' ... I am saying it is worth getting a FSM and really studying it... and following what is says to do....

ollo · #42 11-27-2015, 02:55 PM

He has an FSM, so looks like we are all on the same page. Looking forward to hear how it all turns out. Would have been easier back in the day if I had a FSM instead of a sketchy Haynes plus whatever I advice I could glean from dealer techs. Don

mannys9130 · #43 11-27-2015, 06:44 PM

I attended an automotive technology school as well, and our shop was very impressive and our instructors were very knowledgeable. Now, I doubt the instructors have specific experience with 617s, but they can offer relevant basic info along the way. The specifics would be in the FSM.

I wonder if you could extra credit Ukranian. Maybe ask an instructor if it's a possibility. It probably isn't, but if you could make up something detailing your process maybe they'd throw you a bone for it.

Simpler=Better · #44 11-29-2015, 08:39 AM

Quote:

Originally Posted by engatwork

Yes. I just went through this exercise on a 606 engined 98 E300. You will need to look up where to position the crank and then how to properly position the injection pump prior to inserting it in the timing sprocket.

2x

Don't sweat the naysayers, it's not that hard just think about stuff before you slap it together, and turn it over by hand a couple times when it's together. Use plenty of oil when assembling.

The FSM link has all you need to know: Crank at TDC compression, pump at the right marks, assemble, check pump timing with drip method, and you're set. I did mine in a barn, it's just about following the steps & making sure you're lining up by the right marks.

MrUkrainian · #45 12-03-2015, 12:22 AM

I got the whole block apart and gave it a nice spray of fresh black paint today. Before installing the crank and pistons, i need to put in the new rear main seal. I am a little confused on how it works and havent found much info on what to do. The block has half of the seal and the oil pan has the other half in it, but the new one is one piece. Am I supposed to cut it in half so that there are two "half moons"? The FSM says to leave about 1mm out past the edge but I am a little confused as to if it is supposed to be cut in half? If it is, why wouldnt they just make the new seal in two pieces?