Engine sounds like there’s pebbles in it

[MPitrucha]

I have a 1993 Massey Ferguson 1020 gear driven 4wd tractor with 1600 hours on it. Yesterday while going to park it a sudden noise just started randomly. It sounds like pebbles bouncing around inside of the engine. It does it while idling, driving around, really any time the engine is running no matter what else is going on. The sound seems to be coming from either inside the bell housing or inside the crank case. Definitely somewhere around the middle to rear of the engine on the bottom or middle of the block. I’ve checked for anything external that could be making the noise but everything seems intact. Any help is greatly appreciated, thanks in advance.

 

[Midniteoyl]

Part of your clutch maybe?

 

[fatjay]

Worn or spun crank bearing can sound like that. I'd drain the oil and drop the pan and see what you can find. Not sure how easy it is for your machine, but for the ones I own a visual inspection would be the easiest.

 

[YanmarFever]

Open up the inspection plate on your bellhousing and shine a light in there.
Look for any rivets that fell of the clutch disc and are spinning or bouncing around.
Be sure the brake is set or wheels are blocked if you do it while its running.
I had a yanmar with the rivet problem once.

 

[bmaverick]

If not the bell housing, then drop the engine pan, look up at the crankshaft bearings. If any are bad, carefully do a bottom end engine rebuild. I would not run the machine at this time.

 

[MPitrucha]

Thank you all by the way for your replies, turned out to be fan hub bearing of all things. Guess I got lucky this time!

 

[fc1]

FWIW I love a mechanic's stethoscope for this type issue; makes it much easier to localize the source of the noise.