3720 Hydraulic Problem

[COLD_IRON]

First of all, I used the search function for this problem, found some good advice but nothing that quite fit the circumstances.

The Machine:
2005 3720 - 300CX w/ 4 in 1, 448 backhoe.

The Problem:

I just performed the 400 hour service interval on the transmission as per the service manual. Fired the machine up after I was done to bleed the hydraulics. However, the hydraulics still stutter after running the loader up and down for at least half an hour. Called the local JD dealer and they suggested it could be the new filter being clogged and or causing cavitation...
Guy at dealer said he said he had never heard of this problem before.

I have noticed if the machine is dead cold, it works fine but as it warms up it gets worse. It drives fine, and the backhoe has very little stutter at all, but the loader and all the controls (including 3rd SCV) stutter quite badly.

What I'm wondering is -

a. what else could be causing this stuttering besides air or filter
b. could it be low hydraulic fluid level (it read full on the stick but you never know)
c. possible part failure
d. what else should I be looking at ie Inline filter etc.

Any suggestions would be deeply appreciated

 

[JasonMac]

Could be the relief springs in your couplers.... just a guess....

Loader is totally straight? Not wrenched at all?

Mine has stuttered before half way up the lift cycle before, but the problems has worked itself out... could be filter, couplers, or air. Mine wasn't a big deal though.

 

[COLD_IRON]

Before I changed the fluid the machine worked fine.

 

[COLD_IRON]

Well...

Pulled the filter today, and basically redid the transmission service.

Still runs terrible. I'm gonna have to make some more phone calls it looks like...

 

[radman1]

Not trying to point any fingers, but usually when something like this happens to me, I assembled something wrong or something wrong with the filter. It would be strang to just have something happen to the hydraulic system. Correct oil put in? Any spring or gasket on the filter missing?

 

[COLD_IRON]

I cleaned off the old filter and put it back in, used Low Vis HyGuard as per the directions. Even had my old man double check everything as we were going along (his machine). I'm totally stumped.

I've tried the old filter (cleaned) and a new filter. Machine stutters irregardless.

The higher the RPM's the worse it stutters.

 

[SFish]

Cold Iron:

Describe what you mean by stutter in more detail. Is it stop-and-go, just noise, both? If noise, describe. Maybe you will jog someone's memory.

Steve

 

[drkmstr]

have you changed or checked the inline filter lva14167.

 

[COLD_IRON]

By stutter, I mean that when you work the hydraulics, there is hesitation.

It goes smooth, then hesitates, then smooth again, then hesitates - creating an effect like driving down a washboard road. In fact, moving the loader up and down with the parking brake on - the machine will actually start to move backwards from the motion.

No I have not changed the inline filter. However after reading some threads on here it might not be a bad idea. However - the suction filter was very clean.

I'm starting to wonder if it's the fluid level. Considering the machine has a backhoe and loader, perhaps the dipstick isn't telling the whole story. Dipstick reads full - however it seems I took out a bit more fluid (possibly up to a gallon) then what I put back in. I'm gonna call the dealer in a bit and see for sure.

 

[dirtworksequip]

cidertom, try and isolate the problem. Disconnect the hoe attachment and leave it disconnected. Check the fluid levels- fill if necessary. Now cycle the loader with the hoe still disconnected to see if the shudder is still there.

Anytime that I had ever had a machine act as yours is doing it was always air in the hydraulic system. It always worked its way out. Yours seems not to be doing that for some reason???????

Sincerely, Dirt

 

[COLD_IRON]

Called the dealer.

Missing O-Rings on the filter cover.

 

[dirtworksequip]

That would do it. Glad you finally figured it out. I have not changed the filter on 3520 yet. I'll have to pay special attention to that.

Sincerely, Dirt

 

[Bodgit2]

Hi
Did you clean out the suction screen? Is it proberly reinstalled? Sounds like some air in the system to me also. I've not had that happen to any of my JD's doing fluid change for the universal sump.Perhaps with the loader on and connected, tractor off, crack one of the metal fittings to a hose going to the cylinders up front to let out the air. Start it for a second and bleed it. Shut it off and tighten the line. Stay away from the line when it leaks. Perhaps that will help get the air out.
Steve

 

[Rara Avis]

Called the dealer.

Missing O-Rings on the filter cover.

Thanks for bringing closure...