Cat 420d fdp10924. This machine has lost boom lift , tilt and steering unless using a rear function at the same time. All the primary and secondary resolvers in the loader valve have been replaced. The last valve that operated properly in the order is the right stabilizer. The stabilizer valve us different from the others and does not have the same resolvers. It does have a compensator vavle ,which I removed and swapped with left out rigger and problem remains. Any ideas where to look next?
You did the priority valve resolver in loader valve?
Yes it have removed and checked ( not replaced) the secondary resolver in the priority valve, looked fine. In the priority valve there is only the secondary resolver so I assume the primary resolver for steering is in the steering valve. I have looked at the steering valve in parts sis , but the breakdown does not specify which is the load sense check. Thanks . Edit from the first post. I replaced all primary resolvers in the loader valve, just removed and checked the secondary resolvers.
Hi I would be checking the SMU resolver orifice. if it is blocked you will lose loader function
Good deal!! The resolver in the priority valve is a different part number from the (3) spool valve secondary resolver part numbers. Thanks
A leaky resolver downstream of the smu that would not effect the backhoe section could also cause a problem for the loader due to that orifice also
The fix ended up being a steering priority resolver issue. That resolver had already been replaced but the seat in housing was beaten out. I noticed this with the valve bank upside-down I removed all the secondary resolvers leaving the check balls in the bank I could then see that the check ball in the SPV was deeper than the other three. New SPV and all works as normal.