Loud concussive thump 953 20Z

[JD8875]

My 20Z was running great as I finished a week long pond project... Then as I was spreading to soil all at once it began a loud concussive thumping sound. I shut it down, opened the engine cowlings and looked for anything obvious. I found nothing so I started the machine again at an idle. I noticed the air cleaner cov rattling so I thought maybe it wasnloose and the primary filter was ratling in the can. Chcked that but no go. When I ooened the air filter cover though I could feel a very strong concussive thump coming from the filter box. I'm thinking it hung an intake valve, broke a valve spring or something of that sort causing an intake valve to stay open. Any other thoughts before I pull the valve cover and head???

 

[Bob/Ont]

Most likely a valve, take off valve cover and check them. Don't run it that way.
Later Bob

 

[JD8875]

Bob that was my thought. I stopped right where it was. I've been out of town for several days working and gonna get back to it this week. Anything special about pulling the valve cover? It looked fairly simple. Didn't look like the cab had to be jacked to do it.

Thanks
John

 

[JD8875]

Finally got a chance to the valve cover off my 953 today and found a broken pushrod on the #3 exhaust valve. The pushrod was bent and showed some sign of rubbing either on the block or the port in the head. Just thought I'd post a follow up. I'm heading to Cat this afternoon for a $27 fix.

John

 

[Scrub Puller]

Yair. . . JD8875.

I'm heading to Cat this afternoon for a $27 fix.

I sure hope it works out that way mate but I have found something usually causes a pushrod to bend or break.

Cheers

 

[JD8875]

I'm thinking it may have been excessively ethered, or the valve lash may have been improperly adjusted as that screw adjuster is turned down further than the others.

John

 

[Scrub Puller]

Yair . . . JD8875

or the valve lash may have been improperly adjusted as that screw adjuster is turned down further than the others.

That kind of makes sense . . . might have been countering for a slight bend in the rod or possibly a spalled lobe, you reckon?

Cheers.