L2650 inconsistent "knock"

[KT7303]

L2650 DT ~ 4000 hours.
Intermittently, I've noticed what "sounds" like a mild rod or crank-bearing knock at idle-becoming more noticeable under moderate load. The oil level is and has been fine, however, I have lost track of the last time eng oil was changed. Also, I've noticed no additional exhaust smoke or rising eng oil level.

Using a long screwdriver as a listening device, the noise is most pronounced near the top of cyl 3. However, sometimes the noise appears to come from the transmission. Odd, yes. I thought I'd toss this out there on the off chance someone has run across this before. Thx KT

 

[cthomas]

Perform oil change with the proper grade for your weather(including filter) and change fuel filter/try some fuel injector cleaner for diesel as maybe you are hearing diesel knock. Run for 5 hours and reassess concern.

 

[North Idaho Wolfman]

A video with good audio is always helpful!
With that many hours it could very well need a rebuild.

 

[KT7303]

Thx for the replies. If I can replicate the issue, I'll try to vid. I'll also perform suggested maintenance.

 

[KT7303]

Update: I've not been able to upload the vid of the issue from my iPhone. That said, while videoing, I did notice the 'ole girl appears to smoke a bit more under load.

I'll look further as time permits. thx KT

 

[KT7303]

Hmmm, while searching other threads, the topic of gas in the dsl arose.

This past summer, I mistakenly dumped several gallons of gas into the nearly empty fuel tank. I realized my blunder before starting the tractor; I siphoned the contaminated fuel and filled the tank with dsl.

It seemed to run fine, however, there were times when I thought the engine was a touch noisier. I mention this on the chance it may have something to do with my current issue.