4020 hydraulic chatter

[Anonymous-0]

1969 4020 diesel. Chatter noise from the hydraulic couplers when the hydraulics are idle. Noise lessens immensely when 3 pt arms are lifted. I have had the tractor to the dealer and we have replaced the pump drive couplers (don't remember if the pump drive shaft was replaced), rebuilt hyd pump and steering valve, replaced priority valve, changed filters and screen, rebuilt the brakes, and checked the pressure at the SVC. I'm out of ideas as everything works fine but the noise is driving me crazy (short drive). Thanks for listening.

 

[happysmith]

You have close center hydraulics.

If I were a betting man I would bet it is the pressure bypass-pressure regulator valve chattering to maintian pressure when you aren't using any hydraulics.

 

[JDemaris]

When you say the pump was "rebuilt" - what exactly was done to it? A worn stroke control valve and seat in the pump can cause those symptoms.

 

[MSM]

Probably have an internal leak in the rockshaft valve or one or both of the remotes. Start the tractor cold and let it run at 1000 rpm for about 20 minutes,feel the remotes,diff lock valve the rockshaft,steering valve etc. If warm to the touch(warmer than surrounding metal) the function is leaking. It is leaking enough to just stroke the pump,giving you the chatter noise you are hearing

 

[Bob Roese]

Where is the pressure bypass regulator valve? Is it in the valve body below the operator's left foot or in the pump? Also, what would need to be replaced, the spool or spring? Thanks for your help

 

[Bob Roese]

Don't know. The dealer "took care" of me. Scary heh? I may end up pulling the stroke control valve and seat anyway just to check. Thanks.

 

[Bob Roese]

Thanks, I'll check it out. The SCVs were replaced with ISO couplers instead of JD but I don't know what kind of job they did in replacing them. Thanks.

 

[JDemaris]

The SCVs, steering valve, rockshaft and hydraulic pump all have valves and seats that are similar in design and can cause internal leaks. The original SCV valves were steel-faced, and the replacements are plastic-coated.

 

[Dairy Farmer in WI]

mine does the same thing. all the time. the hydralics will chatter until you raise the 3 pt. have no idea why. but for some reson mine has gone through 2 hydralic filters in 2 months. guess it's time to flush the system.
DF in WI

 

[Bob]

Sounds like your brake linings may be coming apart and getting in the filter.

 

[happysmith]

To be honest I am not a John Deere man, but replied based on my experience with both open and closed hydraulic systems I have dealt with over the years.

A 4020 may have more than one pressure regulator valve governing seperate parts of the hydraulic system.

It sounds like when you aren't diverting part of the pumps output by using the hydraulics that is when you hear the noise.

It might also stop the noise if you were to connect a remote cylinder to one one set of your remote ports and then move the cylinder which would also divert some of the flow momentarily stopping the noise.

I assume the noise is worse at only certain RPMs and is most likely the worst at near idle ??

I would think that somewhere the spool, the spool bore or both, might be slightly worn.

Hydraulic fluid, like water, is not really very compressible and when the gears in a hydraulic gear pump are pushing against high pressure it creates tiny pulses that resonate through the hydraulic system.

Every hydraulic system has a certain resonant "sympathetic" frequency at which the pump pulsations will create noise and vibration much worse than at a RPM that is slightly higher or lower than the resonant frequency.

Every hydraulic system is different and some don't seem to be noisy at all and others sound like they are about to shake themselves apart.

When you divert a portion of the flow causing a momentary slight drop in pressure the pressure regulating valve stops having to regulate and the noise stops.

Where the valve is I don't know, but that is where I would start.