Cat 248 Aux Hydraulics problem

[Steve Frazier]

Since my 2000 Cat 248 (6LZ00433) was new I've been able to release the pressure from the auxiliary hydraulics to change tools by turning on the ignition without starting the engine and then triggering both sides of the auxiliary hydraulics with the buttons on the joystick. I can see the hydraulic lines sag when the pressure is released. This stopped a couple months ago for some reason. The hydraulics work fine when the machine is running but won't bleed off the pressure when not. I can't hear the solenoids opening like I could when things were working.

I've been able to check all the fuses in the fuse/relay block and they're all good. It would seem for some reason the hydraulic solenoids are no longer getting power when the machine isn't running. To clarify, the machine key is in the "run" position when I attempt to release the hydraulic pressure. Does anyone have any insight? Thanks!

 

[Tyler d4c]

Pilot accumulator. If memory serves the solinoids just valve pilot pressure. If the accumulater went flat you wont have reserve pressure to operate the valve

 

[Nige]

An easy way to check if the accumulator is working. Raise the bucket all the way to the top and shut off the engine. Turn the key to the run position and try to lower the bucket. If it doesn’t move the accumulator has no charge.

 

[Deimos]

If the accumulator has a service nipple, try pressing it. Either nitrogen or oil will come out. If it's oil, replace the accumulator. If it's low on nitrogen, you can refill it with nitrogen.

 

[Steve Frazier]

Thanks everyone! I'd have been chasing an electrical gremlin that doesn't exist. Is this a DIY repair or a "don't try this at home" job? Also, if the nitrogen has leaked out should it be tested for a leak before charging?

I'll check the lift arm this afternoon, I think Nige may be right, I think I tried to lower the bucket yesterday with the machine off but it didn't drop. I'll confirm that later.

 

[HarleyHappy]

You can order the stuff to refill an accumulator or just bring it to a place that does it. Be aware, if you’ve never done it, it’s not like filling tires, even though it has a valve core.
One little hit of that valve core, will release a fair amount of nitrogen.

 

[Tyler d4c]

Some of those little hand granade accumulaters come prefilled and cant be charged.

 

[Nige]

Some of those little hand granade accumulaters come prefilled and cant be charged.

I think is one of those. Actually too small to fit a charging valve to it.

 

[Deimos]

For safety reasons, hydraulic accumulators must be stored and transported discharged. At our dealership, they were stored in a warehouse without nitrogen. If a customer purchased a hydraulic accumulator, they also purchased a service for charging and installation. There are two ways to charge the accumulator: through a vehicle's own nipple and using special nitrogen charging kits. If the accumulator doesn't have a nipple, it has two plugs, an external one and an internal one with a hex key. In this case, a special nitrogen charging kit is required.

There are also charged hydraulic accumulators, but they are disposable and cannot be recharged.