Haulin_in_Dixie

Ok have it torn down. Lot of carbon in the cylinders, especially around the exhaust valves. Probably the noise, piston hitting carbon. Also a lot of soft goouey sludge on stems etc. Several valves at point of pitting and most not sealing right, but none really burned. Most off center, have a hunch that they were ground bad, too many sealing on half the valve head.

So, question is how come? I don't idle it, I 'm **** about it. I did leave it running for a couple of hours on 1200 rpm with air on a couple of weeks ago. But running hard 2000 miles since then should have burned it out.

Cylinders are like new, full cross hatch. No marks in pistions so has never been floated. Not quite sure how to clean carbon out of between cylinder and pistion above top ring.

Any ideas? Wonder if the larger housing on the turbo could cause carbon build up? Engine spends most of its time at 1800 to 1900 loaded and pulling.

wannadiesel

I don't see an exhaust brake in your sig, those can cause a lot of carbon in the ports. I am surprised that it would have more than a surface coating with the way you work it. How much waste oil are you burning, percentage-wise?

Water/meth (or just straight water) would keep 'er cleaned out inside.

Dr. Evil

Carbon....I believe is usually caused by quick cool downs and premature shutdowns. Quick cooldowns (including heavy hauling in the mountains/hills) can coke the oil in the turbo causing carbon deposits. In some cases, the carbon deposits can plug the piston cooling ports which will result in a teardown. Ive been told that synthetics prevent this.

Haulin_in_Dixie

This is why it is so puzzeling to me. I am **** about shutting down at 300 pre turbo. Oil is only burned that comes out of the truck, that means 2 gallons more or less in 7000 miles. I use Power Service over half of the tankfulls. I don't remember the exact mileage but about six months ago the head gasket was leaking anti freeze so pulled it and the condition was not like this.

Now it does have leaky valves (not a good seal on most valves), a separate problem that is being rectified now. Only thing I can come up with is the large turbo housing is allowing buildup due to lower boost at cruise. Boost at cruise is 10 or below depending on highway conditions.

Other than the carbon I have come up with no reason for the knock in the engine. Must be the carbon buildup. Does look like it was contacting at the piston build up around the exhaust valves.

Dr. Evil

Biil, Im far being very knowledgable - this info was passed on to me from a 30 year Cummins specialist...good luck with it.

Have you done any/many runs in the mountains or hils??

Haulin_in_Dixie

I am climbing hard as a regular diet. Short hills and then steep down grades so the temperature (egt) is up and down constantly. Climbing is always over 25 pounds boost, up near 1200 and a little over going up and then way down on the down side.

Now the large turbo housing gave it 100 or 150 degrees hotter climbing.

This engine has given the power to pull the hills in overdrive and only one or two that I go over cause a downshift. I think I will be dropping a geat sooner to keep the revs up.

Dr. Evil

Interesting...could be on to something here.

AAmeeting

I saw a cummins L10 engine piston that was being reused on an engine at a cummins dealership hear in indianapolis. Their piston had that carbon you speak of above the upper ring between the cylinder and the piston. They said that it was normal. I thought it was odd because it looked like it was flaking off. That maybe could cause a valve to stick open or not close all of the way. I hope it goes well for ya. T

Haulin_in_Dixie

I might get with you on that after it is back on line. I just hope the noise is gone

See I just pulled the head from the other engine (the cracked block) and it is spottless, no carbon at all. It ran the same injectors, did the same work in the same truck. It should also be the same cam and compression that this one has.

Dieseldude4x4

The last time I had something off the intake for whatever reason, there was a lot of carbon build up in the intake. Someone said it was the Jacobs causing that.

Geico266

I don't want to start a war, but MY bet is it's the burning of waste oil. Take some diesel and oil in the mixture you are talking about and burn it. Granted it won't be the same as running it through the engine, but the sludge is still there. The black smoke (carbon) condences inside the engine and gums up the valve stems. Sludge is sludge.

Burning waste oil in a diesel is just a way to get rid of it for truckers on the road. I just don't think its a good thing if you can avoid it. I just don't see the benifit and here is a perfect example why NOT to burn waste oil.

JMHO.

Haulin_in_Dixie

Well taken, but I would doubt that it has anything to do with it. Here is why. I change the oil at 7000 miles. That is at least 588 gallons of fuel, pulling my loads. After an oil change there is roughly 2 gallons that end up in the tank at two quarts at a time, every other tank of fuel.

That comes out to .0034 gallons of oil per one gallon of fuel. And on tear down it had about 9000 hard working miles on it since it had any oil in it, and actually add another 6000 miles to it so 15,000 miles since it had drain oil in it. I did not put it in the last oil change because of the problems that I was just getting into.

I just don't think that is a factor. And Cummins allows 5% for proper running. I don't go looking for drain oil, I only put in what I know is clean, well changed oil, mine.

rockwithjason

WOW!! A civil debate! And on the internet no less! What happened to the good ol days of flame wars?

AAmeeting

Waste Oil? I think you may have found your problem. Ya ever seen a 2 cycle engine that was ran too rich, Lots of carbon. Why bother? Just give it to the recyclers. My .02

Haulin_in_Dixie

Sorry guys, I forgot to comment on it, the cylinder with the worst carbon had a ver loose intake valve guide. I did not pay particular attention to the rest as I replaced the head, but the seals seemed to be a bit flakey, so that is probably the problem, oil sucked into the intake side.

About 18 or 20 of the valves were off center on the sealing. Yep that many of them. I bet they were ground off center as the head seats were worn nicely, just the valve was seating off center with half of the seat contacting.

Incidentally this was a Cummins factory built engine. The head was poor in condition after 100,000 miles. The cylinder bores as new. Hone lines even at the top ring turnaround.

On the waste oil, the old engine had 241,000 on it when torn down and was clean with the same oil use. The second engine that got 6,000 till the block cracked, and 10,000 with it cracked, was spottless as new. Just took the head off it and installed it. Yeah, I have three ISB engines here.