What should I replace in OM617 rebuild?
 

We're putting an OM617 from an 85 300SD and a 4 speed from an 83 240D into an 83 300D for my dad. Currently, the engine is out on the stand and we're rebuilding it. It ran beautifully but figured it was worth tearing down before putting in the car to minimize issues down the road. My friend pulled it down to the bare block and is wondering what is typically a good idea to replace on these things. The car it was from had 300K miles but it seems like the engine may have been newer than that because it did run well. Note, we will use OE gaskets and such to avoid having issues down the road.

So yea the few basic questions:

What should I probably look at replacing/resurfacing/whatever?

What are things people might overlook doing this job?

Are there any brands to stay away from when considering these parts? I know to stay away from the Victor Reinz head bolts and Febi tensioner, anything else?

Any general advice?

I recommend getting a factory manual and following the recommendations there. Measure everything and if its in tolerance let it be. If not follow factory recommendations. It is quite possible at that mileage it could be fine to use as is and just replace seals and gaskets on the bottom end.

Or it could have been gone through already. I'd have measured taper and bearings before taking it apart.

Cam chain guides and oil pump chain guides along with new chains if needed.

And look at the head. Since its out I'd prob do a valve job. again, measure things and if they're in spec reuse. If not replace.

The harmonic balancer bolts are funny.

Clean up the head castings-you will know what I mean when you see htem. They're necked down pretty badly.


If you're going hog wild you can balance the pistons, etc.

I've got the PDF of the service manual, going to have GT central printing print and bind it for me, it's 532 pages, costs $2.50 from them, which I think is less than the cost of paper if I printed it myself, let alone the cost of ink!

Measure compression on all cylinders. If good (say >380 psig all), I would leave the head on and just replace journal bearings (rods and mains) since cheap and easy. If bad (<300 psig any) you must pull the head (unless just due to bad valve adjustment). If you had large blow-by, replace the cylinder liners - then machine shop hone cylinders and deck the block. Then piston rings and might need some used pistons if any have chunks missing at the ring grooves. Have the head checked and/or refurb'ed while off. Look for my post on removing the liners (easy, flat screwdriver peels cast-iron away from block).

Either way, replace the oil pump nylon tensioner while in there since cheap and cracks. Replace the front crank seal (easy to mess up crankshaft notches for damper so read first). You can replace the rear rope seal with crankshaft in if you lower it slightly (see Rollguy's post).

In sum, the most important thing is diagnostics first. Don't jump into fixing something which isn't broken or you may needlessly mess up a good engine.

Too late he's already stripped it I believe.

Can I be your dad? My wagon would like some attention. :D

no!;)

I would have liked to do all the diagnosis beforehand but my friend has already pretty much stripped the thing. I'm taking classes this semester and can only go down there about once a week so he's doing the bulk of the work. He's a trained service tech and has been working on Mercedes diesels for as long as I've been working on Mercedes diesels and has rebuilt engines before so I think we'll be fine.

That's a great thread. I'll have to get all of the sealants described although I think some of those can be replaced by the Mercedes anaerobic sealant. I have that and some of the Permatex High-Tack which I have because it's used for resealing cloth surrounds on vintage speakers interestingly enough.

THANK YOU FOR THIS!!!

Preparing for a 617.950 rebuild my self.

You will need a triple square long metric, the bit is 10.80 free shipping from snap-on and 45 for the 3/8 socket bit. I have heard you want to avoid stripping the head bolts AT ALL COST. I figure starting with a quality tool and cleaned bolt heads would be a good start.

Going to hold off on rebuilding this engine. The head had some pitting so we decided to try a wagon engine we had sitting around that we were going to sell. Connected the SLS lines to the reservoir that I filled with hydraulic fluid, popped on our 38# flywheel, connected up an exhaust system and filled it with new oil. We connected up a battery then cranked it over without glowing the glow plugs because we wanted to build oil pressure before it started but it came to life rather quickly and ran very smooth for a bit (incredibly smooth considering it was just sitting on the floor). Minimal smoke, pretty good considering how long it had sat. Doesn't seem to have any major leaks unlike the other engine. Probably going to use it but once it warmed up, it started having a lumpy idle, but did idle at full oil pressure. Going to rebuild the lift pump and runs can or two of diesel purge. If that doesn't fix it, we'll pull the injectors to test how well they function.

poor idle could be injector issues or poor compression. I'd run a leak down to see if its leaking combustion pressure.

I guess I can do a valve adjustment as well. Gotta figure out where I put my leak down tester...