Knock Knock

[Gamagoat1]

Several months ago my M816 developed a knock, a loud one. No drop in power, oil pressure or any of the standard indications. A light blue haze from the exhaust that wouldn't go away was all that was evident. Well, after narrowing down where the knock was, #3 piston, I disassembeled it. I'm adding a lot of pictures so you can see what's in side these monsters.
I took the pistons to Cummins and they diagnosed the problem to be too much use of Ether. Then I took it to a Cummins Mechanical director and he said "if the engine had been purchase by me from Cummins it would be a warrenty item and they would repair it. He called it "cylinder liner distortion" and it should have been caught at time of assembly. Oh well, 2 new liners, 2 pistons,rings and bearings and a bunch of gaskets and the big guy is purring.
I hope these pictures help someone understand what's under the hood

 

[clinto]

Great pics, thanks for posting. Good grief, those rods and pistons are HUGE!

I do have a couple of questions………

It appears you only pulled the center cylinders because that's where you found the knock… Did you leave the outer cylinders as is, or did you also pull the heads and inspect them and just not post the pics?

If you didn't pull the outer heads, how do you know those cylinders aren't distorted and just aren't worn badly enough to start knocking (yet)? Do the cylinders typically only distort in the center or in pairs?

Thanks

C

 

[Gamagoat1]

Knock Knock again

More pictures

My sincere thanks to Will Wagner for the help in figuring how to index the oil cooler when there were no index marks from the factory.

 

[Gamagoat1]

RE: Knock Knock again

You can see all the skirt area from below when the pan is off. The other 4 cylinders were like mirrors, no wear evident, thankfully. This is the area the distortion usually is found I was going to pull all but the Cummins rep. said to inspect from the bottom, it works. He also said it was probably caused by beating them into the machined counter-bore incorrectly. A cylinder press is the best way.

The new liners were checked real close for distortion after instal, real close..

Yep they are not the little 283 rods and pistons some of us old guys are used to. Want a neat paper weight, the wrist pin weighs 4 lbs.

 

[steelandcanvas]

RE: Knock Knock again

Sweet job Mike, great photos! How far were the liners distorted? +/- .0000?

 

[Gamagoat1]

RE: Knock Knock again

#3 was 18 thousandths after removal. #4 was 10. The book says out-of -round must not exceed .003 at the top and not more than .002 at the bottom of piston travel.
Thanks John!!!!!

 

[Rattlehead]

RE: Knock Knock again

That's a clean motor!

 

[maddawg308]

RE: Knock Knock again

Man, I LOVE step by step photos! Thanks for documenting this for us!

 

[Gamagoat1]

RE: Knock Knock again

Thanks,
ya know I said it purrs, wrong, it growls and rattles like a good diesel should. (Now).

 

[THUNDRLOJ]

RE: Knock Knock again

GREAT PHOTOS! Now, what to do with the old pistons...Plug the pin holes, fill 'em with ice and shove a few beers in the ice!

 

[Gamagoat1]

RE: Knock Knock again

How about, just beer

 

[Alredneck]

RE: Knock Knock again

Sweet article, good intel, clean look'n motor, glad it turned out well. Looks like a lot of time and effort involved getting it done right.

 

[Gamagoat1]

RE: Knock Knock again

Wifey doesn't understand but,,,,I LOVE MY TRUCK!
Besides, don't want to do it again.

 

[Bill W]

RE: Knock Knock again

NICE WORK
Is it me or do the the pistons have really short skirts??

 

[Gamagoat1]

RE: Knock Knock again

For the bore size they are short skirts.

 

[rockman]

RE: Knock Knock again

Mike, thanks for the photos as it continues to remind me the size of these trucks and I only have a duece. How long did this take you to do and easier or harder than a gas engine?

Bill

 

[Gamagoat1]

RE: Knock Knock again

I think it's about the same as a gasser just don't have to mess with spark plugs, points, distributer etc. etc. Nice and big so my old fingers can hold on to it.

It took two full days, mainly because I cleaned and painted it while it was down, and as it went back together. Believe it or no, that gray paint is the same Cummins paint that was on the engine. It's slowly getting darker.

 

[dragonman]

Was your knock really load like a rod bearing was out?
My 813 was knocking really loud, I drained the oil and there were chuncks and flakes in the oil. I pulled the pan and all of the rod caps they all looked good. I havent rotated the cranck to see the bottom of the pistons I will do that today. Im going to talk to a mechanic today.
A friend off mine revved my truck up after it had just been started on a cold winter day. I sounded different after that the exhaust had a tah tah sound to it. I only drove it about 20 miles after that and when I started it back up is when it started knocking.

 

[91W350]

Thanks for sharing, beautiful work! You have to love the Cummins design. Glen

 

[dragonman]

I pulled all of the crankshaft caps today they all looked good.
Any ideas on what to check next? I'm going to talk to the mechanic again tomorrow.
Would a bad bearing in the air compressor cause the knock and mettle in the oil pan?