Can anyone tell me if the extra control valve in the stack on a 855d will interchange with the one that lifts the boom. It appears to have never been hooked up to anything. Any advice appreciated thanks
The machines sometimes left the plant with a extra valve, for a field install of a ripper/4x1/rear winch/quick connects. If you look at your loader section it has a detent on the lower end to place it in the float position which the other valves do not have. If the machine had the valve for a rear mounted backhoe on it that would have the detent also in the lower end. Some of the lands on the spools are different and are fit to each section for leakage and spool clearance so it does not stick or bind. The shuttle ball and o rings in the rear facing the seat, back of valve section should be screwed out and replaced, also on the bottom of each section there is a screw in shuttle valve with o rings that can be changed out. You should have a fitting on the pump tube going into the valve that a pressure gauge can be hooked up to, loader lift at full height, 2000 rpm should be 2450-2600 psi for checking the main relief. You have to have a hand pump to set the reliefs on the a and b ports. Loader lift b port is 3000-3100 psi, loader bucket a port1400-1500 psi, loader bucket b port and all auxiliary valve a and b ports are 2700-2800 psi. So if it was me I would check the centering spring on the bucket valve that it is tight, change the o rings on the shuttle valves, and go from there. There is a lot going on with the inlet outlet sections and regeneration valves and reliefs. I will give it some more thought also.
Thanks for the info I have a gauge on the way t check pressure of pump. Do they make a fitting to go between the hydraulic lines and the control valve or is there another way to check the pressure there. Thanks again
pressure test port On the lt hand side facing the valve, the top tube going into the valve ( that's the inlet/outlet section) should have a plug or a fitting with a male test port under the rubber cap if equipped. You may remove the plug and drill and tap to 1/8 pipe thread for a test point if needed, then plug it with a 1/8 pipe plug. Or you can buy a fitting at your hyd shop 1-1/6-12 o ring boss male to a fitting of you needs to hook up. The case p/n for the fitting is 218-5316 and R55912 for the male test port, but then you have to have a female coupler to hook your gauge pressure line to. Always release pressure on the system before unscrewing fittings. If you haven't looked at the control valve parts section, you can go to the casece parts lookup on line, type in 855D and then go hyd section on the drop down, once you select the valve section, say inlet outlet it will bring up the pic and parts listing. The inlet/outlet has several spools that should be checked for missing o rings, broken springs, freedom of movement (spools and poppets) you have something that's allowing your flow to bypass unless the next spool in line blocks flow for the loader lift function. You may not be able to get a good pressure reading with just the loader lift until you find the bypassing issue.
Thanks as soon as my gauge gets here and I check pressure I will go into the valves really appreciate the help
Thanks the secondary shuttle valves was the problem. Appreciate the help
My Case 855D runs great, except that there is low pressure on the backhoe. From what I’ve read, there may be a sticky relief valve, or some bit of metal or crud stuck in there. But I can’t find good photos of the valves, and don’t know how to get at the relief valves. Anyone know of a reference? Sheepfoot, you seem to know a lot about these machines. Any ideas?