JD 310b Backhoe: Stabilizers, boom, and crowd all drift!!!

[FuzzDaddy09]

I have an older 310b, the stabilizers, boom, and crowd all drift down with the tractor running. Any ideas as to what causes this. Maybe a leaking relief valve?

[ilander]

I have a JD510, it's old just like I am, and we are both worn out. Yes, my 510's boom and swing drift or sag when parked. This is because fluid is bypassing worn cylinders or control valve.

The relief valve should only function when the control valve is operating and sending oil to a given cyclinder. Once the control valve closes for that cylinder, that circuit should be locked. However, if the packings in the cylinders are worn, or the cylinders are deeply scratched, or the control valve is worn out, then this could causes this drifting.

JD has all sorts of complicated gadgets in their hydraulic systems that really take some head scratching to figure out. So if your boom, stabilizers do not sag or drift when the unit is parked, and only do so when digging, then you may need a JD technician.

This stuff is very expensive. My 510 has a 16 cylinder radial hydraulic pump on it, it trashed itself last year and a new one costs over $5,000, but a outfit called Kin-Tec rebuilt it for $900.

[FuzzDaddy09]

Thanks for infomation. But what I don't understand is it all falls when the tractor is running, parked or in operation. Every 15 mins I have to reach back and pull the boom up. The packing in the cylinder is fairly new...less then a year old. Theres no visible hydro fluid any where. The stabilizers fall at the same pace, one is no more then the other. I recently pulled all the relief valves and replaced all the orings in the units and cleaned them.

[J_J]

You can check each cyl by putting a needle valve in the cyl circuit.

You can also check each cyl by retracting and remove base end hose from the cyl and apply pressure to the rod end, and if fluid continues to flow, then the seals are leaking.

If all cyl check good, and to check valve spools leakage, it is necessary to have dynamic pressure on the cyl, such as a boom raised up, then turn engine off. If booms descends, then the spool is at fault.

The spools spring center parts not function correctly, can cause a cyl to move.