OM617 cracked head, comfirmation please - PeachParts Mercedes-Benz Forum

JayKray · #1 10-26-2011, 07:51 AM

Hi All,
I just pulled a OM617 that I planned on putting in a toyota pickup, however, I went to adjust the valves last night and noticed this. I was hoping it was a scratch, but I'm thinking it is more likely a crack. This is on the valvetrain mounting lobe between the 4th and the 5th cylinder. If the head got this hot, is it likely the entire block is toast? Is it worth keeping?
Thanks,
Jay

Stretch · #2 10-26-2011, 08:09 AM

Hey Jay,

Welcome to the forum - it is difficult to see if there is a crack in the pictures - have you tried some penetrating dye?

The only way to be sure if the mating surfaces are knackered is to measure them - or get a machine shop to check it for you. I'd be surprised if the block was dead for that reason though...

JayKray · #3 10-26-2011, 08:52 AM

Thanks Army!
Yeah, the picture didn't come through very well, I haven't pulled the head to check the important mating surfaces. I was hoping to just use the engine as is for a little while, to make sure I was happy with the swap. Now, I'm thinking I need to dig deeper, or look for a new engine. It ran, but was smoking, previous owner thought it was because the turbo was worn out, which it definitely was. There was blow-by, but it didn't seem horrible. I haven't received my diesel compression adapters yet, but I'll do that before I pull the head.

I was just hoping somebody has seen this crack before, as in my experience, similar motors usually crack in similar places.

I'll try another picture.

Stretch · #4 10-26-2011, 09:04 AM

I haven't seen a crack there before but I haven't seen all that many engines - it doesn't look like a crack to me it seems too straight. The OM617 isn't famous for cracked heads - it is famous for being a non stop 'tractor" engine...

It looks to me more like a machining accident! Does the crack go down into the rough casting below the machined surface?

JayKray · #5 10-26-2011, 09:22 AM

Quote:

Originally Posted by Army

It looks to me more like a machining accident! Does the crack go down into the rough casting below the machined surface?

Yeah, that's what I need to check, I couldn't really tell last night, but I'll get some cleaner and die and see if I can see if it continues down the sides of the boss in the casting.

barry123400 · #6 10-26-2011, 09:26 AM

I like Amys ideal. Take a dremel tool or something and level off and polish an area at the end of the crack on the vertical surface. If there is really a crack you will see it. Of course if you can see a line in the rough casting surface with no work you have your answer.

You could also grind down a little and polish an area on the mark itself. Again if it is a crack it will still be there. I also agree with Amy it may not be a crack.

Your reposted picture is great compared to the original. I sense a slight sideways displacement as well along the mark. It may just be my imagination though or optical illusion. If so it is cracked.

Reasonable maginification like a jewellers loop also might allow you to determine what it is.

Cracks on 617 heads are not very common. Defining rare is hard. They are not totally unknown though. Not so with mercedes next series of diesel engines unfortunatly.

t walgamuth · #7 10-26-2011, 10:51 AM

It does not look like a crack to me either.

JB3 · #8 10-26-2011, 10:59 AM

Quote:

Originally Posted by Army

It looks to me more like a machining accident! Does the crack go down into the rough casting below the machined surface?

x2. looks to me like someone set a fly cut too low for one pass. Can you feel a ledge one way or the other? Do you have a machinist's square you could lay on the surface and see if light gets under it on once side or the other?

That way you could determine if the line is a surface height difference, which would make it more likely a machinist mistake.

JayKray · #9 10-27-2011, 09:00 AM

OK, looks like you guys might be right, I filed and sanded the area at the edge of the crack/scratch and it looks to be OK. I didn't find any die around, but I smeared some dirty oil in the area and nothing really showed up. So, I either smeared metal over the crack while filing, or it was just a machining or assembly mistake.

Now on to the front main seal, the harmonic balancer looks as though it was practically glued on with a green epoxy or bearing retainer compound. I'll try heat tonight to see if I can get it off, but I wasn't having much luck last night.

barry123400 · #10 10-27-2011, 09:37 AM

Unless the front seal is currrently leaking I would leave that damper alone. As you mentioned it appears to be glued on. Chances are the original mating was messed up when the damper came loose perhaps a long time ago.

This is a weak point and if the other persons repair appears to be holding up well I would leave it alone. Also there is a chance what you see was preventative in nature when someone changed a front seal. I would not count on it though.

Can you get hold of the past owner of the engine? He might be able to tell you some things about it.

JayKray · #11 10-27-2011, 09:47 AM

I'm pretty sure its leaking pretty badly. I am in contact with the previous owner, so I will ask. However, I know the engine was a replacement from a junkyard, so unlikely that the previous own did the work, but possible.

I'm reading all the info on here about the tricks for reinstalling the balancer and I will take care while doing so.

Stretch · #12 10-27-2011, 01:06 PM

Good to see no crack

If you're not sure about the front crankshaft seal or the repair post up some more pictures.

barry123400 · #13 10-27-2011, 02:34 PM

Quote:

Originally Posted by Army

Good to see no crack

If you're not sure about the front crankshaft seal or the repair post up some more pictures.

Yes there is absolutly no evidence of a crack there. You really polished it up nicely as well.

barry123400 · #14 10-27-2011, 02:35 PM

Quote:

Originally Posted by Army

Good to see no crack

If you're not sure about the front crankshaft seal or the repair post up some more pictures.

Yes there is absolutly no evidence of a crack there. You really polished it up nicely as well. You are posting some really good pictures .