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JWoodham · 02-26-2013, 11:21 AM

Last summer I was driving my 2000 Monaco Diplomat 315 hp when the engine lost power. I thought it might be an injector as it felt like loosing a spark plug wire in a gasoline engine. However when the mechanic got to it he found 3 lobes of the camshaft severly rounded, one tappet broken and 2 others severely worn. I sent a letter to Cummins about this but got no reply so if anyone has had the same problem I would like to hear from you as no one seems to know how this could happen. I thought these engines were good for 500,000 miles and mine had only 50,000 at the time so I wasn't expecting a $6,000 repair bill.

00MonDip · 02-26-2013, 01:23 PM

Can you give us any history? Are you the original owner? What kind of verified maintenance did the coach get? Did you ever have an overheat, or any caution lights recently? What kind of load are you pulling on a regular basis?

I have the same engine, and I will be curious to see if this is isolated.

Koop · 02-26-2013, 01:54 PM

The cam lobe wear and tappet damage indicate lubrication failure. These questions come to mind:
Are you the original owner?
How often was the oil changed and what API service grade oil was used?

Mike Canter · 02-26-2013, 02:28 PM

This can also be caused by incorrect heat treatment of the cam shaft when it was made. If you still have the old cam then have the Rockwell hardness checked. It would seem to me if it was a lubrication problem then it would have also resulted in failure of the rod bearings.

Koop · 02-26-2013, 02:44 PM

Quote:

Originally Posted by Mike Canter

This can also be caused by incorrect heat treatment of the cam shaft when it was made. If you still have the old cam then have the Rockwell hardness checked. It would seem to me if it was a lubrication problem then it would have also resulted in failure of the rod bearings.

My thinking is that a 12 year old coach (granted, I don't have mileage information) isn't likely to indicate a defective cam hardness. These types of failures usually come early in use.

Lubrication failure often shows up in the valve train. The lobes are not pressure lubricated and are subject to shearing of the lubrication film.

Just MHO after more than 30 years in the auto business (currently employed by a European manufacturer in the Service and Quality Group).

Mike Canter · 02-26-2013, 02:56 PM

Not sure that I can agree. First we don't know the mileage and it is probably pretty low mileage for a diesel. This probably just didn't happen in one trip but has been wearing for sometime. I am saying that the cam probably just wasn't hardened enough. Yes I agree that something may have blocked oil flow to the cam area so it lacked in lubrication. Whatever the problem is I hope they fixed it when replacing the cam or it may happen again.

I got your thirty years beat by twenty in hands on building of drag racing motors as well as tame everyday motors. Currently on a Swedish professional racing crew that races both in the USA and Europe

nodine · 02-26-2013, 05:04 PM

Quote:

Originally Posted by Mike Canter

Not sure that I can agree. First we don't know the mileage and it is probably pretty low mileage for a diesel. This probably just didn't happen in one trip but has been wearing for sometime. I am saying that the cam probably just wasn't hardened enough. Yes I agree that something may have blocked oil flow to the cam area so it lacked in lubrication. Whatever the problem is I hope they fixed it when replacing the cam or it may happen again.

I got your thirty years beat by twenty in hands on building of drag racing motors as well as tame everyday motors. Currently on a Swedish professional racing crew that races both in the USA and Europe

The OP said the coach had 50,000 miles at the time of the failure.

Bob

Mike Canter · 02-26-2013, 05:14 PM

That's not many miles on a diesel

palehorse89 · 02-26-2013, 05:18 PM

That should just be starting to loosen up and run good not have problems like that.

CampDaven · 02-26-2013, 05:29 PM

Okay, maybe not totally relevant, but I had a cam on a V8 chevy that wore down one lobe due to being improperly hardened. 1cam, 1 lifter, 1rocker arm, that was all.
This was at about 50K miles. It went another 210K miles before I sold it.
BTW, I am totally anal about oil and such.
It CAN happen.

nodine · 02-27-2013, 05:41 AM

Quote:

Originally Posted by Mike Canter

That's not many miles on a diesel

Not disagreeing with you Mike. You said we did not know the miles and I was just pointing out that the OP said it had 50K at failure.

I have owned 4 diesels and 3 of them did not eve run good until they got 30K miles on them. The 4th was a motorhome that was so terrible I traded it after owning it for 3 months. It was new when we purchased it so did not have many miles at all.

Bob

jdecastro · 02-27-2013, 07:57 AM

I had the same failure 3 years ago at 39,000 miles and $6,400 dollars later was back on the road. I now have 68,000 miles with, hopefully no further problems. I also bought a new exhaust manifold because the labor to install new or old was the same and they do crack. I hope to have no further engine problems until they take my keys away.

RustyJC · 02-27-2013, 08:13 AM

Assuming you're referring to the C-series (8.3L) Cummins, a little internet searching will reveal that camshaft wear wasn't unheard of on the older engines. The newer ISCs use roller cam followers.

Rusty

greatlakes · 02-27-2013, 08:19 AM

Also in the automotive industry for 25 years developing components and running engine dynos. I would say without knowing the history of this engine it could be either or. The improper hardening is very possible but surprises me that it happened all at once. The lack of lubrication is prob more common as we have no idea if this engine was serviced properly or ever had other issues such as a broken component that could have been fixed but left a broken piece lodged in the oil galley blocking it.
However if it is a lubrication problem hopefully they will find out why otherwise you will be fixing this engine again.