MF Hydraulic problem

[Rob Holmes]

Our 6470 has got some hydraulic issues, it has the 110 l/min load sensing hydraulics;

• When using spools 2 and 3, then levers return to neutral the pump keeps pumping, they feel as though the cables have stretched, but I've been told Boden cables don't stretch, they break.
• Spools 2 and 3 have lost their detent
• When linkage is used the hydraulic pump sometimes keeps pumping.

Some of the suggestions I've been told is that the valve slices need stripping down and cleaning, or the shuttle valve is sticking, another is that the load sensing line is pressurising and demanding pump to kick in

Any other suggestions?

 

[Speedstar]

We had a problem like this on a 7618 , it took some sorting out ,as any oil leaking back ramps the pump flow up , check the control valve on the side of the pump and make sure all the one way a check valves in the return lines are all ok , it could turn out to be a very big job

 

[Rob Holmes]

How big?

 

[Speedstar]

How big?

Ours turn out to be a 10 k job to put right

 

[Rob Holmes]

Ouch!

 

[dee]

Screw the end cap of the spool you will probably find the spring for the detent has disintegrated resulting in the spool not returning to neutral

 

[Pheasant Surprise]

Some of the suggestions I've been told is that the valve slices need stripping down and cleaning, or the shuttle valve is sticking, another is that the load sensing line is pressurising and demanding pump to kick in

Suggestions above all make sense, a strip down of the valve chest ought to reveal any broken springs,sticking or worn spools, problems with shuttle valves etc. The latter could be causing issues on the sensing line, and putting the pump into stroke/pumping.

The compensator in the main pump could also require adjustment or repair, but a good hydraulic specialist with a proper test bench could bench test the pump/compensator to make sure it’s within spec. Should the compensator assembly require replacement, sometimes it’s cheaper to replace the whole pump complete with compensator than buy just the compensator (if it’s even available to buy separately, sometimes they’re not)