Where are the three bolts that hold the plastic screen on top of the engine? Did you remove them for the photo?

 

I did not. The tractor started to clamor and shake and it was exactly like this when I opened the hood.

 

 

I cannot find the bolts. Why all of a sudden would this happen? The cap seems to be warped from engine heat. It is possible that the bolts worked loose overtime, but coming out that way at the same time seems odd.

 

Just one of those things, it happens. High vibration things like mowers and tractors can cause most anything to vibrate loose over time. When you replace the bolts put some blue thread locker on them and you’ll probably never have that issue again 😎

 

I agree, it does seem odd that all of them would come out at the same time. When is the last time you were certain they were all installed? (not a criticism... I've certainly got stuff that might have been loose or fallen out that I'd never notice)

I would pull out the fan housing to make certain they did not fall into the engine anywhere. Also make sure the threads on the lower bracket are still good.

Some purple Lock-Tite on the new bolts would help with vibration issues.

 

Excellent question when was the last time I noticed that the bolts were all there. I don’t know. I do know that the engine shakes violently when I start right now and I hesitate to even turn the key.

 

The violent shaking sounds like a balancer came loose. I've seen this on other john deeres. The vibration may have worked the bolts loose over time but you wouldn't notice until they were all loose. As the bolts loosen up it may cause the plastic gaurd to bend and over time causes a warp appearance. Could you post a video of the macine running for 20 - 30 seconds? That would help diagnose or confirm my suspicions.

 

I am going to the hardware store to get new bolts, I will take a video when I get back. I did remove the cap and took off the intermediary three prong bolt bracket and the engine started and did not make any racket at all. I suspect that the violent shaking was from the misaligned bracket and plastic cover.

 

Expanding on what Peter E said, about removing the the cooling shields to look for the lost bolts, but to also be sure that the cooling fins aren't blocked by bits of that foam rubber thing. Might take the opportunity to brush them out too. You certainly don't need overheating as the next problem!! Good luck!!

 

The violent shaking sounds like a balancer came loose. I've seen this on other john deeres. The vibration may have worked the bolts loose over time but you wouldn't notice until they were all loose. As the bolts loosen up it may cause the plastic gaurd to bend and over time causes a warp appearance. Could you post a video of the macine running for 20 - 30 seconds? That would help diagnose or confirm my suspicions.

I cannot find the bolts. Why all of a sudden would this happen? The cap seems to be warped from engine heat. It is possible that the bolts worked loose overtime, but coming out that way at the same time seems odd.

I agree, it does seem odd that all of them would come out at the same time. When is the last time you were certain they were all installed? (not a criticism... I've certainly got stuff that might have been loose or fallen out that I'd never notice)

I would pull out the fan housing to make certain they did not fall into the engine anywhere. Also make sure the threads on the lower bracket are still good.

Some purple Lock-Tite on the new bolts would help with vibration issues.

 

If the engine is shaking/moving in the cradle I would check the engine mounting bolts as well to make sure none of them are loose/lost!

 

My guess is that two of the three screws have been gone and the third one finally loosened enough for the flywheel cover to come uncentered and sling around. That off-balance weight is what caused the severe vibration and chewed the foam air seal to pieces, and then gave the flywheel cover room to lift, and the last screw let go. The top of the engine cover is scoured by the cover spinning around. Does the engine run smoothly with the cover off?
That foam ring should be replaced, it seals the top of the engine when the hood is down so it will pull cooling air from outside the hood, which is much cooler than the heated space under the hood. Most JD models of the late 90's through mid 2000's are made that way, my 2002 GT235 is the same design.

 

Just one of those things, it happens. High vibration things like mowers and tractors can cause most anything to vibrate loose over time. When you replace the bolts put some blue thread locker on them and you’ll probably never have that issue again 😎

My guess is that two of the three screws have been gone and the third one finally loosened enough for the flywheel cover to come uncentered and sling around. That off-balance weight is what caused the severe vibration and chewed the foam air seal to pieces, and then gave the flywheel cover room to lift, and the last screw let go. The top of the engine cover is scoured by the cover spinning around. Does the engine run smoothly with the cover off?
That foam ring should be replaced, it seals the top of the engine when the hood is down so it will pull cooling air from outside the hood, which is much cooler than the heated space under the hood. Most JD models of the late 90's through mid 2000's are made that way, my 2002 GT235 is the same design.

thanks to you and everybody else who participated in this discussion. The engine runs exactly like it did before, pretty smoothly, now that the cap is off. I’m going to replace the bolts from a John Deere dealer, the bolts. I’m finding at hardware stores don’t seem to match, even though they are the same metric size. While I am at it, I may as well do an oil change and sharpen the blades. Get her ready for next spring.

 

Like 'inch' hardware, metric hardware can have different thread pitches.
Instead of being identified by threads per inch, metric hardware is identified by millimeters per thread. (the thread pitch)

Fwiw, the flanged head bolt used in that application is used on many Deere machines (not just lawn and garden equipment)

 

Looking a little closer at your pictures, it looks like maybe there’s more missing hardware. Down on the front of the frame below the grille, on the shroud on the John Deere label, way down below the dipstick tube, etc.

 

I think Deere standard sizes for both metric and inch hardware have 'coarse' threads.

(not suggesting that there aren't special situations where the use other thread pitches)