Just had Hydraulic control valve on Bobcat T300 rebuilt. Lift and tilt working like new , but can't get auxiliary spool to function. It's a one piece valve , paired with manual foot controls. It will open the teeth on my grapple , but will not close the teeth. So , fluid not returning. It has a stem in front , and a stem on back of auxiliary part of valve , and a coil solenoid on each stem. I measured 12 volts on each solenoid when I toggle auxiliary switch . So, this rules out no voltage from the controller. I believe the rear stem controls the return . I replaced rear stem and solenoid , and front stem solenoid only. No change. Teeth on grapple , still stuck open. Any ideas? Is it possible to assemble auxiliary spool incorrectly? Any help would certainly be appreciated.
A T300 is a G series machine. If you're not getting 3 beeps from the alarm then there's no fault with electrical control of the auxiliary circuit, which would mean you have a mechanical problem with the circuit, something the BICS doesn't monitor. The two electric coil cartridge valves that you're checking are actually pilot valves that are used to shift a spool inside the main control valve. First thing I'd do is swap the aux cartridge valve and see if the problem reverses. If it doesn't, likely you have something wrong with the aux control spool inside the main control valve. One other possibility, there's a circuit relief valve on the circuit that goes to the male quick coupler for the aux circuit. There's no circuit relief valve on the female coupler circuit. If you're weak function is the one connected to the make quick connector, you might want to check that relief valve cartridge.
Its probably pretty unlikely, but could something be stuck in the check valve for the aux circuit and it won't let it open (not sure if its on the male or female side of the coupler)
Hey. Thanks for input. I have replaced all stems and solenoids. Everything is new now , unfortunately issue not resolved. I spoke with shop that did rebuild for me , and he said aux spool only goes in one way so not chance of installing incorrectly. Would charge pressure sensor , that's on back of valve , on top of auxiliary valve have any relation to this?
Did the aux functions work prior to the valve rebuild?
Yes , never a problem with auxiliary function. I hooked up backhoe attachment, and it curled the bucket in as soon as I started the machine ( fully extended the rod from cylinder). Didn't even turn auxiliary circuit on. The bottom auxiliary coupler (female), is difficult to attach , and remove. A lot of pressure. Is it possible to incorrectly install a spool?
Don't know myself, haven't done a T300 valve before. But it everything worked prior to valve rebuild I think I'd be going right back to the rebuilder, he's missed something.
Could he have forgot a centering spring on one end of the spool and it is stuck in one position? If you aren't even activating the hydraulics and its got pressure that would be my guess.
I agree. I think that spool is stuck in one position. I think I can get to that spool , with valve installed. That's no easy task , removing and installing that valve. Probably get a Bobcat tech out first to confirm. Thanks for replies.
in my s300 I have done that spool without removing the valve its not a ton of fun but it can be done and would be less work then pulling the whole valve. If you get the caps off the centering springs / bushings and o rings are all right there nothing internal other then the spool itself. Its the easiest one of the 3 spools to work on (the one on top of the valve when installed in the machine.) On the s300 there is an access panel above the rear axle if the T300 has one if you can remove it, it will make the rear much easier to get at, but I am thinking the center panel and the rear panel are probably covered by your tracks and may not be as easy to get to as they are for me.
Right. Was going to try to resolve with valve installed. That access panel doesn't do much good , unless track is removed. I hate to spend the money , but I think I will have Bobcat tech confirm , before I proceed.
Yep. Bobcat tech confirmed, auxiliary spool not functioning at all. Internal problem. I disassembled from and rear blocks, and removed auxiliary spool. Hydraulic shop assembled aux spool incorrectly . Keeper and spring assembled backwards , so spool wash pushing against block, not spring. Also , shop lost original keepers, so made some . Those had a 1/4 inch lip , as opposed to 1/8 inch lip , and they were installed backwards. I reinstalled with correct parts, in correct order. Auxiliary spool is now functional. Sad to say , but job took me about 8 hrs.
Glad you got it all sorted out