normal or abnormal wear???

Chevycummins

Chevycummins

Bad case of Tinkeritis!
Joined
Jul 15, 2008
Messages
3,488
well about 4 years ago i purchased a used 12v engine to use in my conversion. was told it had about 150k miles on it. i have since then put about another 100-150k on it, odometer never worked just hand calculated on based on trips made. never had an issue out of the engine at all made good power and ran great. me and my brother have decided to build another truck and put the 12v in it.

i decided since i have it out to tear it down and rebuild it just to be on the safe side. started tearing it down and everything looked good til i pulled the cam , rod caps, and main caps. i didnt get any pics of the cam, but you can see most of the damage done to the rod and main bearings in the pics. some of the gouges in the main caps are probably close to .030 if not more. the rod caps appear to mainly be normal wear, but curious as to where the pitting and gaulding came from. oil was changed every 3-5k miles, and also leaked pretty good that fresh oil was always added frequently. what surprised me about the rods and mains was the crank was just fine only the bearings were tore up.

on the other hand i noticed something odd on the pistons. it looks like there was possibly blowby but never seen any from the blowby tube or when the oil fill cap was removed. there is still visible cross hatch on 2-5 cylinders. only 1 and 6 looked like it was starting to show signs of a damaged ring or debis in the engine.

the cam had slight pitting on the bearing and some pitting on the tips of the cam lobes. the lifters looked fine and didnt show any abnormal wear.

this is what 1 and 6 look like:
2012-04-29143911.jpg


this is what 2-5 look like:
2012-04-29143845.jpg

2012-04-29143839.jpg


this is what the rod bearings look like:
2012-04-29143756.jpg

2012-04-29143738.jpg


this is the sides of the pistons:
2012-04-29143722.jpg


this is the main caps:
2012-04-29143711.jpg

2012-04-29143705.jpg


in the pics of the main caps you might be able to see how deep the gouges are in the bearings. its really noticeable in the last pic of the caps of how bad the damage is.

because there was no damage done to the crank i am surprised how bad the bearings were. there was no tick or knock in the engine to give any signs of bad bearings. what could of caused this kind of damage and is there something i should be looking for when we go to put this back together to prevent it from happening again?
 
Let me get this straight, you tore down a cummins diesel 12 valve motor with roughly 300K miles, correct?

And the pictures above are some of the wear and tear you found?


I've never torn down a motor with that many miles, but i suspect if it was above stock horsepower level for any of the last 150K miles, the wear and tear is normal.
 
Cylinder damage looks like engine got hot. Find a lot of that in engines that tow a lot. Naturally 1 and 6. Bearing damage could be excessive miles, poor maintenance/contamination or both. Normal rebuild and it'll be brand new.
 
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When I received the engine it was a stock 190 hp engine. I then changes injectors and turbo, along with the few pump mods reached 438 hp at the rear wheels.

I was young and dumb when I got it and believed the guy that I bought it from. He told me if it would turn over it would fire. Sure enough it fired right up when we put fuel to it. bigblue to answer your question, I really don't know the exact miles. I put what I roughly knew and what I was told it had prior together.
 
If that's what that engine looks like I'd be curious to see what the one in my old truck looks like considering it's been modified since it had 20k miles on it.
 
Yeah but yours doesn't set and idle or run like a school bus, which its what this 12v came out of.
 
yeah if i had the knowledge i do today it would of rebuilt when i first got it. instead i listened to someone at a diesel shop that i thought knew what they were talking about instead of just trying to sell me something. :doh: i am not ashamed of it by any means it had run great and put out more power than i thought it would do without an intercooler. just was shocked at the damage i had found when torn down.
 
Looks like they might have let the maintenance slide, never know how it was treated or taken care of, but I bet it was running just as happy as a lark wasn't it :D
 
school bus miles are murder on an engine. I did an engine in a 98 Ford school bus with 80k and I've seen pickups with 3 times the miles and 2 times the horsepower look a lot nicer then that engine did. I'd say it was just wear and maybe they ran the oil a little long and got it hot.
 
That wear looks normal to me. I have seen much worse. The thing is you don't know the life it has had since new. It is what it is.
 
seeing some brass showing and even across the bearing would look normal to me. the deep gouges that are only in the center are whats got me and its not even worn to the brass like the rod bearings are.

gonna start looking for parts to rebuild it and get something to measure the bore and see if its gone too far to use standard rings or if it will have to be bored. so far as the rods and mains i can stay with the standard. also i have 5 Brazil rods and 1 Japanese rod so i will find another Brazil rod to have all matching rods.
 
In failure analysis training, the pitting on the bearings was attributed to acid buildup in the oil. They probably ran it hard and did not change the oil very often.
 
That its possible before I got it. I changed it every 3-5k miles. Oh well lesson learned. Check any used engine before installing.
 
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