On my 2006 Bobcat 331-G, I am trying to bleed off hydraulic pressure to the boom, etc when the machine is at rest. I have the "deluxe" control panel...the one without a key, all pushbutton (I don't like this). The manual says to play like you are going to start it, just don't hit the start button...make sure the console is down and manipulate all levers to bleed the pressure. I don't see or feel any pressure release at all . Anyone got any insight on this ? Thanks for any help, Pete
Not sure why you want to bleed off the pressure in the cylinders when the machine is at rest, but the info given in the manual isn't completely accurate if the machine has been off for a period of time, actually not that long. It takes pressure in the pilot system to operate the valves that control the cylinders. A better method would be have the engine running, safety bad down, then shut the engine off. Immediately after the engine stops turn ignition back on and work the joysticks, there should be some residual pressure in the pilot system because of the accumulator, but it won't be much and will dissipate rapidly.
Thanks, Willie. I am assuming one should bleed off the hydraulic pressure by working the controls after shutdown ? Maybe it's not necessary ??? At any rate, I will try again. No key to turn.. After shutdown, the panel stays powered up for about 30 seconds..temp gauge, fuel gauge working...that's when I worked the controls to try to bleed off. Do you think I should just not worry about bleeding down ? Thank, Pete
I'd wager simply resting the bucket on the ground would be sufficient. After all, the cylinders are designed to accept and work with pressure to do the work. Additionally, even if you bled off the pressure in a cylinder at a given moment, as the oil in the cylinder cools down from being at rest the oil contracts which causes oil to be drawn into the circuit via anti-cavitation valves. The next day when the sun comes up and it begins to get warm it heats the oil in the cylinder, the oil begins to expand, but it's now trapped, and just like that you have pressure back on that cylinder that you previously bled down. Physics at work.
Thanks Willie. I'll just forget about bleeding off. I appreciate the help. Pete
I have only had to bleed pressure off of my thumb/Aux circuit when using a breaker, packer, or screw pile head. I run CATs and Kubotas (<8tons) and the reason for doing this is to be able to loop the disconnected attachment hoses (protect couplers/ minimize contamination) or to bleed off any pressure from fluid expansion before connecting an attachment. Willie mentioned a reason why pressure may develop and later need to be bled off. There may be a manual relief somewhere on your machine (I have seen them in wheel loaders and skid steers, but I can't think of one in my mini-x's. May I ask why you wanted to bleed the pressure off of the cylinders?
Hi Rev and thanks for your input. I was thinking bleed off is a good idea. Hate to leave pressure on something. Guess it's ok with these machines tho. I have found in my operating manual the correct procedure to do so. I have been doing it wrong. Will try the correct way and see if it works (just for the heck of it...ha) Working on machine and cleaning it up....coolant change , oil change, greasing and more greasing....adj tracks etc etc....have not even dug a hole yet. Weather is really messy here. Not on a schedule either. Can work with it at my leisure. Thank you, Pete
Willie, isn't it shocking what a little temperature change can do. Dropped a 37 ft kit out of a CMI mainline concrete paver on a cold fall morning. Made the changes and went back under the next afternoon. Temp was 45 degrees warmer then. Had to break the quick connects loose on all 36 vibrators to bleed off the pressure before we could plug em together. Actually took a bit to figure out what the hell had caused it...