knocking noise

[ruffdog]

My NH TC33D would sound like that once in a while. It was only at mid rpm and low load, just like the OP's tractor. My tractor was a 1999 and it never got worse with age and never made the noise while working. I would check the crankshaft thrust clearance with a dial indicator prying the crank forward/backward. If that checks out, I'd let it go. It doesn't sound like top end noise like piston/rod as those make noise right when throttle is applied. Excessive crank thrust will make noise at certain unloaded rpm's and when you chop the throttle. Like I said, verify the clearance, if ok, run it.

 

[rScotty]

{UPDATE} Mine (original post) has been at the dealer since 6-30-2020 now. I checked on it Friday. It's not an exhaust issue. It not anything loose on the outside of the engine. It's not a throwout bearing or clutch related. (HST). They were going to check the valve train next. I hope they get it resolved too and it's not something major. I only had the little guy a few days but I sure miss him already.

Sounds to this old mechanic like they are on the right track.
rScotty

 

[PILOON]

Am going way off topic with this----------

Had an airplane develop a slight knocking while I was at 5000 ft.
Would only knock when on both mags.
Really scratched my head thinking as to what it might be.
Knock got louder by the minute and as I cut power and the engine stopped dead!

Later teardown showed a crankshaft counterweight broken lose and jammed itself under a piston.
Thankfully I did chop power when I did otherwise pieces would have flown everywhere.

No injuries other than ego and a damaged aircraft.

 

[K5lwq]

Am going way off topic with this----------

Had an airplane develop a slight knocking while I was at 5000 ft.
Would only knock when on both mags.
Really scratched my head thinking as to what it might be.
Knock got louder by the minute and as I cut power and the engine stopped dead!

Later teardown showed a crankshaft counterweight broken lose and jammed itself under a piston.
Thankfully I did chop power when I did otherwise pieces would have flown everywhere.

No injuries other than ego and a damaged aircraft.

That is not fun! At least you had altitude to give you a little time to find a place to put the plane down. Could just as easily happened just as you clear the runway. Glad no one was hurt!

 

[nosaj2]

Sounds to this old mechanic like they are on the right track.
rScotty

That is good for me to hear Scotty.. I hope you are right.

 

[nosaj2]

[UPDATE]
The dealership could not determine what was causing the knocking sound. They had the Branson rep come down. The Branson rep suggested that they send it back to me and for me to drive it hard. I guess until what ever is causing that comes loose. I don't know. But I guess that is what I'm gonna do. They said they would replace it if it came apart.

 

[K5lwq]

Would be interesting to know what all they checked. When you get it back see if you can duplicate the noise without moving the tractor.

 

[TimberHole]

My wife took her car to the dealership a few years back for a noise. Every time she backed up it made a weird clunking sound. After 3 techs spent about 2 hours on it they figured out it was a can of hairspray rolling around under the drivers seat! :laughing:

 

[metalbender]

I can relate to strange noises. Back in the mid nineties, at the Mercury dealerahip, had a fancy Grand Marquis with a squeaking noise inside when turning corners. Was in the shop a couple times, techs couldn't isolate the noise. Also wasn't there on very humid days. Frustrated customer as well as the service manager. Finally came around to my turn. No flate rate, straight time, please take time to fix this. A ten minute drive with the shop foreman driving, me listening, the offending noise was located. Customer had a St Christoper medal on a key chain hung on the rear view mirror. It swung with the turns and squeaked till it stopped swinging. Service manager clocked me in for two hrs, thanks.

 

[rScotty]

Would be interesting to know what all they checked. When you get it back see if you can duplicate the noise without moving the tractor.

I still don't understand if it could make the noise when not moving? If it could, then I would do the following:

Yes, I'd still check valve clearances and the clearance on the compression release. That isn't a total of more than one hour mechanical time. Of course what they have for mechanics today are more like warranty part replacers. Their mechanic and service rep may neither of them ever set valve clearances. It's commonly done at 600 to 800 hrs.If so, I wouldn't want him learning on mine.

As for checking if the noise is a rattle coming from the EGR valve, it is simple to just find the rubber pressure hose from the manifold to the EGR mechanism and disconnect it to test. Pliug the hose temporily with a pencil. It's usually a small diameter hose - roughly 1/4 " diameter and fits onto barb connections.
rScotty