m18s intermittent knock/rattle

[jigbuilder]

My '92 1862 cub/50" mower deck with the m18s Kohler lost half of its engine oil right out the end of the low oil pressure switch. The light never came on. As I finnished mowing and brought the engine down it rattled/light knock at idle. I changed oil and filter along with a new pressure switch. Now it knocks/rattles only on occassion when it idles.

I've used the cub since '94 mowing 2-3 acres a week in the summer so it has lots of hours. The engine doesn't use oil.

Does the m18s have a known light knock/rattle at idle with lots of hours ?? Any ideas ? I plan on tearing it down this winter.

Thanks..........Jim

[Matt G.]

They all have valve noise at idle, regardless of hours, it seems.

[tower512ladder]

I have a 1541 with about 1000 hours. the motor is nearly identical to your M18, mine is just detuned to 15 hp. I have noticed the same kind of noise on occasion from mine. As Matt stated above I believe this is a not uncommon "occurance".

[ol'George]

Is it a knock or a valve clatter?
A knock is audible by grasping the throttle linkage and lightly advancing the rpm's @ low speed
you will hear it as the rpm's increase, Rap,rap,rap
it's more of a lower pitched noise.

Noisy valves are usually quiet when the engine is cold, but increase as it reaches operating temp.
As matt says, most are noisy after many hours of use.
Use a stethoscope or a long handled screwdriver or stick placed to your ear to see if it is valves.
They will be most pronounced @ the exhaust manifold, rocker box covers & intake manifold/head intersection.
I hope for you it is just normal valve clatter.

[squatch]

My M18 had a tacking/knocking sound after last winters work. It sounded a lot like a rod or maybe head gasket leak. It ended up being a slighty loose baffle in the muffler. I replaced the muffler and it is now gone.

[jigbuilder]

Thanks folks. The lite knocking/rattle goes away as the rpms go up.

I let it run for 15 minuets at 80 percent throttle this afernoon then brought the rpm back to idle and no rattle or lite knocking. The engine is still very quiet when cold but is a bit noiser at idle with normal operating temps.

I noticed the Kohler service manual on their web says;
Crankshaft splined insert lube interval recommendation

Says to seperate the oil pump from the engine every 500 hours and lightly grease the male portion of the pump spline. It mentioned pump spline damage or tooth damage to splined inserts. I just noticed this in the online service manual and was wandering if anyone has had this issue and could it be a source for my intermittent noise.