Good and Bad engine wear - what to look for

[TylerS]

I'm tearing apart and rebuilding an lmm I picked up that had a cracked piston. I was wondering what wear indications to look for both good and bad. I'll post some pictures of the cracked piston later but I know it's nothing new.

Pictures are always beneficial.

Thanks for the help!

 

[TylerS]

First question I have is what causes the oval shaped, darker marks staggered about cylinder in this picture? I assume it's normal as block is looking good even the cracked cylinder wall is pretty good.

 

[moparkxracer]

Pic didn't post

 

[moparkxracer]

If it kind of looks like cheta spots, it's part of the hardening process from the factory.

 

[TylerS]

Interesting...yeah cheetah pattern is a good way to describe it. It's only towards the top of each cylinder.

Did pic load?

 

[moparkxracer]

Ya it's only the top 2 inch or so. No the pic didn't show. Go to your settings on your profile and click the make public settings.

 

[TylerS]

Thanks moparkxracer - fixed settings on picture

 

[moparkxracer]

No problem, I had the same issue lol.. Ya that's part of the hardening it's normal. Sometimes it will come out if block is honed.

 

[TylerS]

What kind of wear marks should I be looking for on the crank? Some of the casting is definitely less than impressive so wonder if that leads to a crack initiation site.

 

[Hot COCOAL]

The broken cranks are "usually" at the #1 rod journal and have been believed to be caused by harmonic frequency developed from the firing order, which is why there's so much hype around the alternate firing order cam(s)

I think the biggest thing to look at is the crosshatching in the cylinder bore, but your probably gonna need a hone at a minimum to clean up any scoring from the cracked piston.

Crank end play and the cam bearings and main bearings would be next, and then see how much heat and friction the rod bearing took on.

Then how the top ring on the pistons look, look for any scuffing, if it looks "polished" I think that's normal, but scuffing isn't good..

Also check the top and bottom of the cylinder bore for where the piston stops traveling, look for a ridge caused by wear from the rings.

I've only taken one d-max apart
But I've torn a few SBC and a couple LS engines down with a few different people and those are the things I've always been told to look at

 

[NC-smokinlmm]

You mean to say cracked piston or cylinder wall?

 

[TylerS]

Thanks for some of the tips Hot COCOAL. I've been following a lot of the posts on here about the cranks but wasn't sure which side the crack initiated on or maybe its been too varying to identify a typical spot.

NC-smokinlmm, I re-read my post and I can understand the confusion. I didn't word it very well. What I meant to say was that even the cylinder wall that contained the cracked piston looks pretty good. Obviously I will at least need a hone if not a slight over-bore.

Anybody have pictures of bad bearing wear?

 

[NC-smokinlmm]

Look at cocos build thread... Lol...:hug:

 

[Hot COCOAL]

Look at cocos build thread... Lol...:hug:

Lol, yup!

Here's the link-
http://www.duramaxdiesels.com/forum/showthread.php?t=60063

Although this wasn't a failure, it's not what ya wanna see, fer sure.
This is what I found out of a used engine I bought, luckily, I found some actual broken parts as well and was able to return that PoS