John Deere bucket loader troubleshooting guide

[Lord Beowulf]

Hi All,

Last summer the piston rings gave out on the bucket cylinders on my 300CX loader. Now I appear to have a failure back in the SCV that's giving me the same problem. When I originally investigated this last year, I found a troubleshooting guide from John Deere that had step-by-step test directions for isolating the problem, but for the life of me after repeated online searches I can't seem to find it. I don't think I'm mis-remembering it, but it's always possible it was someone's post somewhere. Rather I think I found a post that had directed me to the guide. I'm hoping someone here knows of the guide I'm looking for and can point me in the right direction.

Thanks,

Beo

 

[Dave M7040]

Hi All,

Last summer the piston rings gave out on the bucket cylinders on my 300CX loader. Now I appear to have a failure back in the SCV that's giving me the same problem. When I originally investigated this last year, I found a troubleshooting guide from John Deere that had step-by-step test directions for isolating the problem, but for the life of me after repeated online searches I can't seem to find it. I don't think I'm mis-remembering it, but it's always possible it was someone's post somewhere. Rather I think I found a post that had directed me to the guide. I'm hoping someone here knows of the guide I'm looking for and can point me in the right direction.

Thanks,

Beo

I don't understand what a scv has to do with your loader so a few photos would help.

This procedure has proven useful to many for diagnosing cylinder issues.

Dave M7040

 

[Lord Beowulf]

I don't understand what a scv has to do with your loader so a few photos would help.

This procedure has proven useful to many for diagnosing cylinder issues.


Dave M7040

Thanks for the response Dave. John Deere uses a dual SCV to control the bucket (see this link), so if the cylinders aren't leaking, the problem has to be somewhere back up the hydraulic chain. There's not much else between the cylinders and the SCV other than hoses/tubing, so if I'm not spraying fluid, the SCV is suspect. The guide I'm looking for had a step-by-step test for determining where the problem was, starting with the steps you show to evaluate the cylinders, and then working backwards to the tractor controls. I'd say I definitely have some sort of problem in the control chain, since if I put a gauge on either line for the cylinders the pressure drops down in a few seconds after going to center, and if I disconnect both hoses and drive in the lift direction (if I remember correctly) the return fitting will spray fluid under pressure too. Not sure if that's a problem with the SCV or a check valve somewhere (although I don't see one in the schematic). At any rate, since I was able to remember enough of the diagnostics to retest the cylinders, etc., it turns out that the new piston ring on one of the cylinders had completely blown out. Luckily I had an extra kit since I was going to redo the lift cylinders too although they weren't giving me problems yet. I'd already had the problem that the kit JD shipped was missing the shaft seals, but looking at it now I realize that while it comes with two different width piston rings, neither is actually a good fit for this piston. The width is still a little small and I think it rocks back and forth in the slot and wears out quickly. I'm going to follow up with the dealer so that they can talk to JD.

Thanks,

Beo