555 no hydraulics

[JimFord555]

1979 555 backhoe lost all hydraulics

Checked the tank for a plugged screen or loose baffle restricting fluid

Pulled the pump and went through it and its all good

Removed disassembled and cleaned hoe and loader system over pressure valves

Bypassed the hoe and the loader worked perfect

Switched the hoe system over pressure valve (#3 in the pic 2400psi) for the bucket over pressure valve (#23 in the pic 2375psi) and still nothing works

Problem must be in the hoes hydraulic manifold but other then the system overpressure valve what could stop all hydraulics from working ?

I can get a small amount of movement tilting the loader and that s it

Any help is much appreciated as I don t know where to go from here

 

[Andy Wickiser]

I don't have a service manual for the 555
but have one for my 455d which is several
generations past the 555 but in many ways
similar. Troubleshooting chart says
PROBLEM: All backhoe circuits fail to
operate, are slow or have loss of power.
POSSIBLE CAUSES: Regenerative check valve
in control valve outlet end cover stuck
open or seat is leaking. CORRECTION:.
Back pressure relief valve and unload
valve test.

That said it's speculation that the 555
has similar components in the outlet slice
but something worth looking into given the
steps you have ready taken.

 

[JimFord555]

Thanks , ill check the regenerative check valve once I locate it,

My manual doesn t have that in the trouble shooting section. It just says check fluid levels , pump etc and the 2 system over pressure valves

 

[Andy Wickiser]

Yeah it's confusing. I have trouble using
the new CNH parts diagrams on my
smartphone. Valves are mostly identified
generically as ''HYDRAULIC VALVE''. I
would take a look at the various valves on
the outlet section 37, 45, 50 for obvious
defects. Sorry if this turns out to be a
false lead but you're running out of
possibilities. Might not be able to get a
replacement anyway. I guess you could
take the shotgun approach and buy an
entire used control valve.