OM617 main bearing crank condition - 2nd, 3rd, 4th... opinion required - PeachParts Mercedes-Benz Forum

Stretch · #1 10-07-2010, 10:17 AM

G'day Folks,

Has my luck changed?

After ending up getting the cylinder head rebuilt, the block re-bored, and new pistons for my OM617 (non turbo) I've been told that the crankshaft is good!

Apparently I don't need to worry about the "light scoring" that runs around the main bearing surfaces: All I have to do is to make the crankshaft super clean and polish the journals with a rag and a bit of oil.

I'm looking for a second opinion, a third opinion etc etc etc

What do you think?

(Please take a look at the photo's)

vstech · #2 10-07-2010, 10:20 AM

that scoring in the first pic sure looks bad.
has a crank shop inspected it?

Stretch · #3 10-07-2010, 10:28 AM

Yes I've just got back...

DeliveryValve · #4 10-07-2010, 11:12 AM

Pictures of scoring marks on smooth metal surfaces can be deceiving. It would be best to get another opinion in person. With that said, If you can feel the ridges bumps with your finger or finger nail, then you may need to get it polished by the machine shop.

.

gastropodus · #5 10-07-2010, 11:13 AM

I'm no expert, but I wonder if polishing might be something done with strips of fine grit cloth. I've heard of Bearing Service performing that process here in Portland. I don't think I would use them as is.

Kurt

Diesel911 · #6 10-07-2010, 11:31 AM

Quote:

Originally Posted by gastropodus

I'm no expert, but I wonder if polishing might be something done with strips of fine grit cloth. I've heard of Bearing Service performing that process here in Portland. I don't think I would use them as is.

Kurt

Where I used to work we cleaned up Detroit Diesel Crankshaft bearing areas with Emery Paper and lastly with 500 or 600 Corocas Cloth (not sure or the real spelling or real name).

The Corocas Cloth does not have a raised grit like even 1200 emery paper does.

Before any polishing is done it needs to be measured to see if it is out of round. If it is out of round beyond spec you need to find another Crank or have the original machined undersized.

Diesel911 · #7 10-07-2010, 11:32 AM

How about some pics of the Bearings!

Stretch · #8 10-07-2010, 01:40 PM

Quote:

Originally Posted by Diesel911

How about some pics of the Bearings!

Hey whatever floats your boat!

Here are two shots I've just made (in the dark). I'll take some more when it is light again so that the flash doesn't get in the way.

I have a service history that came with the car that agrees with the reading on the odometer - however looking at the dates between the work done it is quite clear that the car has been sitting doing nothing - well it would have to wouldn't it 160,000 km / 30 years...

It also looks like it could have done with more oil changes - a hazard of buying a low mileage car I guess.

layback40 · #9 10-07-2010, 09:55 PM

Hopefully whunter will tune in & give his opinion !
Best not just use visual, the crank needs to be measured with a micrometer.

Diesel911 · #10 10-08-2010, 12:37 AM

I am wondering how who ever it was sent to could say the checked the crank but did not measure it.

If this Crank was in a proper shop they would also put it in some V Blocks and use a Dial Indicator to find out if it is bent at all.

You can find out something if you turn the Block upside down and install the front and back upper Main Bearing; well lubed with Oil; set up a Dial Indicator on the Central Main Bearing Journal (remember there is no bearing there).

Rotate the Crankshaft slowly so it does not move back and forth and read the run-out on the Dial Indicator.

But, except for the score marks where the dirt went through the 2 Bearings I would otherwise say they could be reused.

Do they have exchange Crankshafts available in Holland?

If it only had 160k-km not even 160k-miles I doubt if it has out of roundness that would be beyond spec. And, the Bearings look like they were getting enough Oil.
I would most likely polish the Journals and reuse the Crankshaft.

The score marks on the Crank did not cause any thing bad to happen to the old Bearings.
After it is polished even less so.

I am going to stick my Neck out and say I do not see any impending disaster from reusing the Crankshaft with normal driving.

It is going to depend on how much quality you want to build into the Engine.

Stretch · #11 10-08-2010, 05:44 AM

Great advice - thanks folks

Stretch · #12 10-12-2010, 09:05 AM

Quote:

Originally Posted by Diesel911

Where I used to work we cleaned up Detroit Diesel Crankshaft bearing areas with Emery Paper and lastly with 500 or 600 Corocas Cloth (not sure or the real spelling or real name).

The Corocas Cloth does not have a raised grit like even 1200 emery paper does...

I too have come across crocus cloth in the past before - here is a link for it:-

http://www.3m.com/product/information/Crocus-Cloth.html

Stretch · #13 10-12-2010, 09:08 AM

Update - the machine shop is pretty busy at the moment - I spoke to some one else and they agreed to measure and check the crank properly and give me a better verdict. (And then if their verdict is not what I expect I'll be checking it myself)

DocSarvis · #14 10-12-2010, 09:25 AM

I agree with the finger nail method for a better check than visual. If you feel the grooves it wont polish out for good results. you want about 1-3 thou between the bearing and crank. anymore than that it will start to knock. A typical human hair is 3 thou so if you "polish the grooves out you will be undersized. Not good. A shop can turn it down 10 under and then you can get 10 over bearings and be fine. hand polishing will only take abot 1/2 thou out and that will still leave the grooves if you can feel them. Dont build a compromized motor. Have it turned down should be relatively cheap Less than 100$ I would think. Thanks

Stretch · #15 10-12-2010, 09:47 AM

Quote:

Originally Posted by DocSarvis

I agree with the finger nail method for a better check than visual. If you feel the grooves it wont polish out for good results. you want about 1-3 thou between the bearing and crank. anymore than that it will start to knock. A typical human hair is 3 thou so if you "polish the grooves out you will be undersized. Not good. A shop can turn it down 10 under and then you can get 10 over bearings and be fine. hand polishing will only take abot 1/2 thou out and that will still leave the grooves if you can feel them. Dont build a compromized motor. Have it turned down should be relatively cheap Less than 100$ I would think. Thanks

Hi Doc(Sarvis) I've still not worked out if you like being called Doc or not!

Unfortunately the cost of machining here is pretty daft. I'm guessing they'll expect about 40 euros per journal. I have heard rumours that a new OM617 crank is about 500 euros - but they are no longer obtainable via the dealer... If I can get a new crank for this kind of cash then I'll probably go for that instead of encouraging the silly labour rates here - and when I go back to England I can get my existing crankshaft refurbished for a reasonable rate and then sell my old crankshaft back here for a silly price (It is all a bit tedious but that's what you have to do to get things done for a reasonable amount here)