Engine/Transmission (1994 - 1998) Head Removed for Headgasket repair, cylinder pics

[keimmmo]

The way I see it, the scores are the RESULT of another problem, and not the ROOT of the problem. If you don't get to the root of the problem, it will only get worse... and will even destroy another motor if you replace this one.



The scores are undoubtedly the result of high temps. The 1800 blasts could very well be the whole problem. However, there are jets under the pistons on our motors that spray oil into the bottom of the piston to cool it. If one of those jets gets clogged, it can cause the pistons and cylinders to score. There are documented cases of Fram filters causing the jets to clog... and that orange filter I see in your photos sure looks like a Fram. I would be worried about just putting the motor back together and running it!



Steve Keim

 

[Highfinance97]

FLEETGAURD!!!!!! Oo. Oo.



Michael

 

[Hohn]

I agree with Steve Keim and Jim Fulmer-- it's EGT.


It's quite possible that at those blasts to 1800 or more, you consumed all the ring end gap that you had, end the ends butted together and the rings fit VERY tight in the bore, and scored the walls.

Of course, it's also possible that the piston itself just swelled up too much from being so hot and the pistons itself scored the walls. It's more likely, imo that the crown of the piston did the damage, because the skirts don't run anywhere near as hot.

The pics you posted above are a perfect case study where thermal barrier coatings may have prevented the scoring/scuffing. Their ability to keep the piston crown from absorbing as much heat will reduce expansion and will prevent scoring caused by over-expansion.

The overlooked item here is TIMING. What, timing? Yes, TIMING. More advanced timing has TWO negative effects on the piston: 1) Increasing temps/pressure at TDC, and 2) Deeper "penetration" of those temps into the piston crown.


Both of the above will cause the piston tops to expand excessively or simply melt.



If you doubt the above, look at how detonation (preignition) often destroys pistons in a gas engine. Yes, you often have physical damage from the concussive effects of detonation. But just as often you will have MELTING of the pistons-- and this is because the concussive effects drastically increase the penetration of the combustion heat into the piston crown.



Suffice it to say that advanced timing AND high EGT is a recipe for piston carnage.

 

[bgilbert]

$8k on engine and transmission but won't spend the extra buck for a good oil filter. C'mon guys quit taking the easy way out of shopping at your local parts house and buying Fram(puke) filters. There are tons of places to buy Fleetguard online. I'm not really pointing this at you Bobcat as the turd filter might not of been your problem, pointing more towards other owners that read this thread.

 

[MHalloran]

FLEETGAURD!!!!!! Oo. Oo.



Michael

I agree, as with all true Cummins owners. FLEETGARD ALWAYS!!!

And yes, I'd also say it's a FRAM (yikes!!) in the picture. The letter "M"

is staring at us.

 

[Jim Fulmer]

A few things here to make note of: Change the fuel return line now while you have the head out of the way... . much easier.



You don't have to pull the manifold or turbo do change the head, merely push it over an inch or so.



Are you still going to put it back together and run the crap out of it! It would be interesting to do a leak down on that cylinder when you get it back together.



Jim

 

[Bobcat698]

Settle down about the FRAM filter guys. . I had to use it in a pinch as nothing else was available. . Even Cummins didn't have a filter. I only ran it for a short time as I needed to make a trip and the oil change was due.



I am putting it back together today. . Going to run the crap out of it!



I wish I would have known about the fuel return line earlier. . Too late now. . I need to get it running today.



Thanks for the info guys.

 

[TravisG]

Jim- I will get him to change out the return line this week or something. Thanks for the suggestion. He is going to add the cooling "thingamajig" in the freeze plug behind #6. Maybe that will help him out a little bit. Didn't get her back together today. Got a little bit busy around the shop. Installing some chip thingy on a FERD. Boo!!!!



BTW thanks for all the help fellas. And keep givin 'Ol bobcat poop for the Fram filter. :-laf

 

[Bobcat698]

Got the motor pulled, I will update this thread when I have the head off, 25k miles later.

 

[biggy238]

I take it the engine went down with flying colors? (or flying oil drips anyway)

 

[Bobcat698]

I take it the engine went down with flying colors? (or flying oil drips anyway)

Nope, drove the truck to the shop under its own power, engine wasn't getting weak or anything, just need to start getting it built for pulling season Oo.

 

[biggy238]

"Elected Repair" would be the terminology

 

[DBraunig]

Bobcat,



Did you ever put that bypass cooling setup on that rear freeze plug? what are the part numbers? work ok?



Dave