We have a 2016 CAT 259D (SN FTL04295) that hasn’t had any hydraulic issues to date. We just bought a brand new hydraulic plow, hooked it up per the manuals, started the machine, and gently started to apply hydraulic pressure to the thumb dial on the joystick. At first nothing happened, but then suddenly while still on light pressure the plow banged full tilt to one side. Then it did that again to the other side when rolling The dial gently backwards. The end result was two broken rams. So the question is, was it some kind issue with the rams or can the CAT auxiliary hydraulic system overpower the hydraulics? It is not a high flow machine And the system didn’t make any excessive noise to suggest the hydraulic system was under high pressure. It sounded normal.
Have you ever used the auxiliary hydraulic circuit before? Did you get to hear the pressure relief valve open, realize it happened very quickly but that never should have happened.
No, we haven’t used the auxiliary circuit before And I didn’t hear the pressure relief valve either.
You might need a restrictor fitting in the plow lines. What is the make and model of the plow?
The cylinders were probably void of oil for shipping, and the first time the cylinder moved with oil it went at warp speed because there was only air in the cylinders. If the thumb wheel was moved a hair too fast, too much load on cylinders. The lines should be tested with a plug and gauge on the end before hooking up to blade to see what kind of pressure is hitting the cylinders. Remember, the first time you hook up the lines to the machine, they are empty and if you move the thumb wheel just a tiny bit, it might take 30 seconds to get the line filled and the cylinder starts to move. If a person decides to roll the wheel most of the way then the oil is travelling high speed to the cylinder with air cushion behind. Too fast and too late. Cylinder rod junked. We had large cylinders at a mine I worked at that came empty also. The first time stroking the cylinder had to be done with the rod end pointing into the air because of the speed the cylinder would jump out. Simon C
Thanks. I suspect they were empty of fluid. I rolled the wheel very gently, didn’t roll it hard at all. Is there a way to fill the cylinders or a method of first time operation so it doesn’t happen again with new cylinders? Nothing mentioned in the cat or plow manuals.
Loosen the cylinder fittings about 1 turn and wrap a rag around the thing before sending oil slowly to it. Would be a good idea to hook up a guage to the end of hose before hooking to cylinder . That way you can see if there is too much pressure. Who made the plow? Could be fairly cheap cylinder, do not know. Simon C
What is the pressure rating of the cylinders that pooped?
Hydraulics over air is a dangerous situation. 2 cylinders might have been luck. Personally, if it were mine, would be calling the people that made it and asking some questions. Then I probably would be putting bumpers inside the cylinders if no good answers.
The plow is US made and they sent us new cylinders. The air-bleed sounds like a good idea. Thanks!
The manufacturer sent two new replacement cylinders yesterday. We will install them, but before trying to operate the plow, we will have the CAT mechanic come out to check the machine to be sure all is well. I think Simon C’c suggestion for air bleeding makes sense, although none of the manuals suggests that. Not sure where air goes if you don’t vent per his suggestion.
The manufacturer sent new cylinders under warranty. We will replace them, and before hooking them up, will have CAT mechanical test pressures, etc
The speed a cylinder will move with only air in it on one side is scarry. I have seen some jump out 6 feet in 1/4 of one second. I know yours are smaller , just saying when the oil hits one side of packing and there is only air on the other side, she moves very fast. Simon C
By the way, glad you got some on warranty. Maybe they will send instructions to the next person to prevent the same, maybe not. Simon C
Today we filled the new cylinders and lines with CAT Hydro fluid, installed them, turned the pressure valve down, loosened the fittings slightly and wrapped them with a rag as suggested, and ever so gently applied pressure. Worked great! All fixed! Tightened fittings, cleaned up, refilled hydraulics lost in original disaster and are now waiting on some snow. Thanks all for the help! And no instructions, but it would be helpful for the next person.
I wonder if he would also need a Cushing or crossover valve on this. What will give first if he hits something, the Cat's relief valve or the plow.
Without a crossover relief valve the plow will pretzel long before the machine's relief lets go.
When I built my 10’ plow, I put in a 1500 psi crossover relief valve and have been playing with it for 3 years now. I have cranked the pressure up a little, especially when the banks are a little frozen. I can see it working, every time I push up on a bank, it will angle back over by itself. I would imagine that it has to have some kind of a relief valve.
I don't have one on mine but I only plow my own paved driveway. I know every nook and cranny of my yard. If I were to take on any outside work, I would install one first.
Thanks for that Tid Bit. Was wondering if you remember where you bought you crossover relief from, Brand , Type, not sure what brand of plow you have. Thanks Simon C
I had to add the pressure relief valve on my Bobcat when I bought the 4-1 bucket. Easy install in the spool valve, remove a plug and replace with the valve. Ed
I bought the pressure relief right from Summit for around 45 dollars. The plow is a Meyers copy from Mass Made by Curtis and I specifically wanted a blade tip over type, as I plow a lot of gravel. I sliced a 2” black iron pipe and fitted it over the cutting edge. The pressure relief block I bought came preset at I think 1250 psi but I have played with it a few times as you can just ease up to something and trip it over to the other side. Not sure i‘d plow without one as you have way more pushing power than a truck.