L2550 What is normal diesel sound?

[Tim Kowalski]

Hello - New to the forum and Kubota tractors.
I recently upgraded from 1950's Ford tractors to a 1986 L2550 DT. I am pretty good with a wrench for the most part.
So, I get a pretty good deal on this 4WD with 1150 hrs and a loader on it and bring it home. I replaced leaky front axle seals, and replaced all fluids and filters.
I replaced the thermostat because it was running low temperature on the gauge. It starts instantly when I turn the key and no smoke except very faint grey for a second or two when I first load it down. Everything seems perfect.

Okay - to my question. The engine seems to have a sharp knock that I believe is diesel knock. I am not sure if it is normal or something fuel injection related.
I am confident that it is not a rod knock or piston slap. There was no debris in the oil pan and all sounds smooth through a stethoscope.

I just don't know what a 30 year old diesel with low hours should sound like. I runs awesome and there doesn't seem to be any lack of power. I can live with the sound - I don't want to mess up the engine if this is something to worry about.

I am used to gas tractors, so maybe it is nothing at all. What do you think? How difficult is it to pull the injectors? There doesn't seem to be anything on that on the web.

Thanks in advance.

 

[Diydave]

2 thoughts,

1 post a video, with the sound

2 if the oil pressure light ain't on, you're prolly OK

I would order a shop manual, and study the section on valve adjustment, particularly if your tractor has around a thousand hours on it...

 

[rbargeron]

Diesels from the '80s make a lot of racket compared to gas engines. If the rap is noticeably different under rapid acceleration in neutral or when under pto load, then there could be a bit of water in the fuel, or an obstructed injector, or possibly a bearing or piston with excess clearance. Does it sound loud all the time or is there a condition when it is different? A shop could test the injectors. With fuel pipes removed they unscrew from the head (use new copper washers).

 

[Dave_eng]

Listen to an early generation VW diesel. If you did not know better you would think they were about to blow.
The early Cummins diesels found in Dodge pickup trucks made an awful racket.
People were willing to pay a premium to get the "big truck" sound.
I dont think you have anything to worry about!!!!
Learn to love the sound of diesel Torque instead of screaming gas engine horsepower.
Dave M7040

 

[rentthis]

Dave, I had one of those Dodge trucks. My neighbor (50 yards away) said she always knew when I got home. The truck woke her up. I bought the newer model and you could hardly hear it. If the knock goes away with acceleration, it's just "diesel".

 

[ShaunRH]

Is the knock metallic in nature? Does it have a clack or clank in it? If so, you might have an issue.

Otherwise, it's probably just fine.

 

[Tim Kowalski]

Thanks for the replies!
The knock is most noticeable when the engine is idling. Is isn't a deep knock like a rod bearing, but sharp knock like a gas engine "dieseling" (as older cars with carburetors would do when you shut them off and kept running without ignition).
I will adjust the valves when I have a chance, but there are no unusual sounds coming through the valve cover when scoping. Just the normal light chatter of the rocker arms.

As far as changes in the knock under different circumstances, it is less noticeable at higher RPMs and non-existent when dropping RPM after releasing the accelerator.

I will see if I can post a video. I know that even then it may be difficult to judge.

I really appreciate the responses. I am kind of obsessed with this awesome little tractor and want it to be as happy as I am.

 

[Tim Kowalski]

Okay, I poked around on YouTube and found some videos of L2550 tractors idling and being driven. I am delighted to report that they all sound pretty much the same as mine. (Not quite like the new ones!)
Thanks for the idea to video. It got me looking.

I appreciate everyone's suggestions and will add them to my limited knowledge of Diesel engines.

I think that I am good to go... for now.