ISX 15 Knocks under load

You could have carbon packed Pistons.. Only way to fix that is a rebuild. How much oil are you using? Also yes a Cummins dealer is IDEA but remeber.. They charge EVERY HOUR they touch that truck. a Dealer has a book time they use... extended warranty only cover book time

 

Sounds like it could be a worn cam. And the overhead is out of adjustment, which could lead to more carbon being produced which is filling your filters and lowering your oil pressure.

Just a thought

 

Yea well, I don't know then. I just know that motor produces A LOT of soot and it really helps to run a by pass filter of some kind to help limit the soot

 

Knocks are usually from over fueling injectors. A cut out test under load would be good way to find out which one is causing it. Here is some stuff from Cummins about oil consumption.
TSB 150163- Excessive Lubricating Oil Consumption on Engines outside of warranty or extended Coverage Period

Some engines may experience an issue with excessive lubricating oil consumption outside of the warranty or extended coverage period.

Please reference Technical Service Bulletin, Anti-Polishing Ring Cylinder Liner Release to Prevent Bore Polish and Elevated Oil Consumption Caused by Piston Top Land Carbon Packing, TSB50069.

Please reference Technical Service Bulletin, ISX15 and QSX15 Early Life Oil Consumption Caused by Vertical Liner Lobing, TSB140030.

To address excessive oil consumption issues on engines outside of the Warranty or Extended Coverage period in a more cost effective manner, a specially formulated lubricating oil, Valvoline™ Premium Blue Restore™, has been developed. Valvoline™ Premium Blue Restore™ can potentially reduce lubricating oil consumption rates on the affected engines by removing deposits from pistons, piston ring lands, and other engine components.

The use of EDS is highly suggested even when engines are outside of warranty or extended coverage periods.


I know your truck is under warranty still, but part of the process for a warranty repair due to oil consumption is to document it. Cummins has a form for this that you need to fill out.

 

It's a guessing game, but I think you have a cracked or a piece of a piston has broken off. Happened to an ISM we had last year. Used it for about 5 months before tore into it and found issue. But was the same symptoms you are describing.

 

If you suspect carbon packing then try out the valvoline restore. If your hearing a knocking, it's definitely not the top end. Top end taps, not knocks.

 

I am surprised that nobody has mentioned the easiest diagnostic tool...........a oilsample.
Get one done asap.