I have a Case 621 that lost pilot pressure for the lift. The steering works fine. I only have 25-0 psi of pilot pressure at idle. After troubleshooting I found the two check valves that connect the hoses from the steer pump and hyd. pump to the pressure reducing valve trashed, the ball and seat was wore out and the spring broken. I have new on order. Has any one else had this problem? Your help is very appreciated.
Sudden? Hello. Is this a sudden failure? if so it may be indication of abuse. If the bucket is overloaded check valves and the like get damaged pretty quick.
it was an intermittent problem the last two weeks and then it completely stopped. the customer is rough on equipment though.
i had that same problem before, replacing the check valves fixed it.
i changed the check valves and you unit still did not work. i was checking hyd. pressure again and could not get any. i did finally get some pressure after dead heading the steering but that was it. i'm leaning towards a bad hydraulic pump. i did check the main relief but that was ok.
those gear pumps are fairly durable, there is a coupler on the drive shaft of the pump, maybe worn out? If you drain the oil to remove the pump, you could take that round plate off the left side of the tank and see how the suction screen looks. We have 5 621's running around never had a pump just quit.
isn't the hyd. pump closest to the trans and the steer pump is piggybacked on that one? so if the coupler for the drive shaft is wore wouldn't the steering not work?
I think so, I know it was that way on the old w-series. I'll look tomorrow. I have a new pump assembly on the shelf I'll look at. Still might be suction screen.
but wouldn't the steering be affected by a suction screen being plugged?
just sayin you might as well look when you drain oil to pull pump, a bit of a long shot. The problem still points to the check valves, there purpose is to keep the boom and steering hyds separate. Its been awhile since I had trouble with on but I will study one for a few today. Is yours a 621 or 621b?
i have a straight 621. i did change the check valves .
today i got the new pump in. i can get the tilt to work a bit but no lift. i pulled the pressure reducing valve out and disassembled to make sure i didn't have any left over pieces from the check valves. everything checked out ok. i was looking at the parts diaghram and noticed there is a low pressure regeneration valve on the control valve i didn't know if this could be a problem or not. i'm getting about 100 psi of charge pressure at idle when deadheading the steering i get about 475. is this normal? i guess i'm also a little confused at how the steering comes into play with the pressure reducing valve. suction screen was clean
tightgtp, 621 loaders built prior to JAK 00202386 have a pressure regulating valve which recieves oil from steering pump & sends 80psi to remote control valves - does yours fall into this category?
my serial # is JAK 00027078. sounds like it does. but my pressure regulating valve recieves oil from the steer pump and hyd. pump. both lines go to a tee going into the valve.
this diagram shows exactly what you describe you should have 550psi at the test point near accumulator while at main relief - (if you can get it ) I guess you've tried adjusting the regulator? with no response at gauge...?
i don't think the regulator is adjustable
just figured how to post this - may help There is supposed to be a allen headed screw under cap (that's what my book says..?) Re : pressure reducing valve - looks like regulator to me.
i'm not sure if you got this out of a service manual but in the accumulator test. what is the pressure reducer?
ok thanks i'll check that. i had it out today to clean the entire valve. i looks just like a cartridge type relief valve. i had no idea it was adjustable. its not a very big cap that covers the allen screw. i hope this is the problem. theres not much left in the system to check. thanks again.
The only one I've had that problem with is a 621b, different set up than yours. We have 3 621s with your set up. looking at pic it almost has to be that valve or you have joystick problems.
i've got 2 joysticks and a aux. valve. all three act the same which points to the reducer valve in my opinion. i'll report back
Well i adjusted the pressure reducing valve and still had the same results. i know its raising the pressure because when i deadhead the steering my charge pressure is higher. what could possibly go wrong with the remotes?
Few questions - 1) Is your reducing valve same as the illustration with long hex body or shorter? (machine ser no. says it's short version) 2) How much pressure does steer. relief give you in pilot circuit? previous post says 475psi. 3) While pressure is in pilot circuit (on steer. relief) does it make any difference to the loader or tilt operation? 3) Does any pressure go to pilot circuit when you try to roll the bucket back - at idle & full rpm?
1-its the same as the picture i would say the hex is about 2". 2-steer relief is around 475 to 500. i was able to get it to come up by adjusting the pressure reducing valve. 3-no, i'm unable to get any loader/tilt/aux functions to operate 4-at idle i'm about 100psi and i can get the bucket to roll back and forth about 6" of stroke on the cylinder. -at full rpm i get about 400psi or so and i can roll the bucket fully back and all the way forward but it won't pick up the weight of the machine.
Looking at this flow chart I keep thinking problem exists in reducing valve or shuttle valves... You say you've replaced them - with new? Could one be faulty? Pull them of & confirm they are working by blowing air through? Have you pulled apart the reducing valve by removing the adjuster screw / spring & plunger?
Still Thinking................It's hard without seeing machine............... Machine serial no says you have pressure reducing valve AND regulating valve. Regulating valve contols 80psi back pressure to loader pilot circuit - could this be what you have? We could be looking at wrong valve.........
if i have that i have no idea where it is. i'm going to look the parts diaghram on case's website.
ok so i was looking at the parts pages. my ser.# is JAK0027078. the serial # you refered to in an earlier post has an extra number. the picture you just posted is for an early 621 according to Case's website.
That's an interesting flow chart alrman. I've stayed away from this one because I don't know anything about this machine, but you've posted some nice info and diagrams. Is the valving on these open center?
my local case dealer tells me this machine is
What happens if you dead out the steering making it open relief valve (which is the 475 lb you mentioned) and operate loader functions right then while steering circuit is on relief?
ATCO, been wondering where the HEF posting bandit was on this one & yes, the main loader control valve is open centre. tightgtp, see what tomorrow brings?.....
LoL, I've been hiding behind this rock watchin' how this played out, just didn't know anything about this machine, but was curious. Your diagrams caught my attention.
sorry i didn't realize this posting spilled over to another page. i have tried the steering deadhead while trying to operate loader and no result. case tells me the steering has priority.
i also went as far to cap off the "back to tank side" of the pressure reducing valve to eliminate the possibility of a bad pressure reducing valve, and that didn't make a difference.
Oh yes, could still be a faulty reducing valve cartridge, stuck spool or something like that. It's the most likely suspect. If the flow chart that alrman posted is true to your machine, I don't know that you would call this system "steering priority". Again, if the flow chart is true. It does always have steer, the systems just uses oil from both steer pump as well as equipment pump to operate pilot system. That way, even if your steering and lifting bucket at same time, oil is available from either pumps to supply pilot system. I would disconnect and cap the line that comes from the work equipment pump to the reducing valve. Dead out the steering, and check pilot pressure. Still no good, disconnect pilot line going from reducing valve to control valve, connect that line straight to a gauge. Check again, pressure still no good, faulty reducing valve. Just a few thoughts I have.
good thoughts, i guess one thing that throws a hitch in this is the fact that i can adjust the reducing valve cartridge to up the pressure and when i deadhead the steering the pressure goes up also. do you think there is a possibility of a problem with the any of my joysticks.but i would think they would also be open center.
alrman would know that better than me, he's the Case tech. Choose your terms carefully about the joysticks, the valves (as I'm understanding it) would be open center, but I'm thinking it's possible the pilot system that controls the valves are more of a dead end, able to retain pressure for operations. The tank line from the joysticks may be to release pressure when you let a function go back to neutral, just a guess on my part though.
ok so here is today's info. 1- blocked of the feed from the hyd. pump to red. valve. , deadheaded the steering and am still getting pilot pressure and i can adjust the red. valve up or down and the pressure changes with the adjustment. 2-installed a gauge in the end of the pilot supply directly from the red. valve. pressure was up to 1000 psi and holding. (it was a 1000 because i still had the red. valve set up higher. 3- capped off the return to tank line from the joysticks pressure was up around 500 to 1000 depending on if i deadheaded the steering. i could really feel the joysticks getting stiffer. 4- installed a gate valve in the pilot supply line feeding the joysticks to see if slowly creating a restriction would raise pressure. still none of these have helped. really starting to pull my hair out. alrman do you have a hydraulic schematic you could post? are the joysticks open center valves as well?
Are you saying you had 1000 psi on the pilot circuit that operates control valves? And it still doesn't operate loader functions? How much pressure does the pilot circuit require to operate the valves? I suggested removing and capping the line coming from work equipment pump to simplify things a bit. First, this takes the check (shuttle) valves out of possible problem, and it allows you to work with a pump/circuit that you know for certain can develop pressure, that being, the steer, because you can dead head it an pop relief, you know the pressure is there to work with then. Now all you have to do is get that pressure to you control valves. I'm curious to see what ideas alrman has, he can take this way farther than me.
yes i did have 1000 psi pilot but only at deadheading. the pilot circuit needs to see 575 psi to work. i still only have 100 psi while requesting lift or tilt on its own.
Where's that dang Aussie when ya need him! :tong Ok, let me see if I got this straight. You have a gauge somehow tee'd into the pilot line going from pressure reducing valve to pilot controls. All lines connected proper except you have blocked the supply from the work equipment pump, removing it from the troubleshooting process. Deadhead steer, still no pilot pressure. Disconnected pilot line from reducer, went straight to gauge with pilot line. Deadhead steer, able to get sufficient pressure on pilot line. Reconnect pilot line to pilot controls, removed and blocked tank line from pilot controls. Deadhead steer, able to get sufficient pressure on pilot line but still no operations. The gate valve? Not sure if it would achieve desired results. Reconnect lines proper, the best you can get on pilot circuit is 100 psi, not sufficient for operations. Is that pretty much it?
there is a factory test port in the pilot line right before it goes into the cab for joystick control. at deadhead of steering i get required pilot pressure needed. yes to direct to gauge and blocked of tank line
i would really like to see a hydraulic schematic, since i have 2 joysticks and an aux lever the conglomeration of hosing is difficult to see in such a small area
Wait a minute, do the functions operate when this happens?
no, the only thing is the buck will rock back and forth about 6", but slow and the unit won't pick itself up
Well, I've taken this about as far as I can not knowing the machine, need to see what the Aussie thinks about it, knows far more than I. Sounds like you may have a problem in the control valve, not sure about that though.
control valve or pilot valves(joysticks)? i did have the thought at the end of the day that i may need to start separting out and block off each section of the control valve one at a time. i am still thinking that my joysticks are open center because i can block off the tank line and everything holds.
Ok Ok I'm here - I'm in the middle of my woking day, here down under tightgtp - you still haven't mentioned whether you have reducing AND regulating valve - the regulating valve should be near steering priority valve.
LoL We gonna drag you in here one way or another.
i have what is in this picture, #19 is called the pressure reducing valve.
sorry the picture didn't show up in the quote. its on page one. i have a late model 621
are you refering to the flow control valve/flow divider as steering priority valve?
1) yes item13 in the lower picture (5-8) is the steering priority valve 2) the pilot remotes are closed centre 3) in earlier post you say you put a gauge directly on the feed to remotes & read 1000 psi due to valve adjustment - was this pressure there all time ? without steering relief ? PS I just read you only get pressure at "deadhead" If you disconnect the feed to pilot valves & put gauge directly into line - there MUST be 575psi there - if not there is problem with shuttle valves or reducing valve is the problem - if you can't see why - replace valve next had problems may times with reliefs on hoes without any visible probs & new ones only way to fix
3- i don't recall what it was, but there was some, after steer deadhead the pressure (1000) stayed
since the pilot remotes are closed center i almost feel as one of the three could possibly be leaking back to tank. but i would assume they are setup up in a parallel circuit rather than series but in my thinking if i blocked the return line from the remotes to tank i would have eliminated a leaky remote
well today was a bust. i blocked of the aux. valve and 2nd joystick and still nothing. the thought came to me today today that how can you have closed center pilot joysticks and an open center control valve that get there oil from same outlet on the pump. how can i ever build pressure in the pilot circuit, but maybe that is where the pilot line from steering comes in. i don't know just brain storming i guess.
Bad news tightgtp.......jobs like this make you wonder why anyone would be a fitter??? Did you notice my last post & what I suggested ? Did you try that ?
Because...we love pain alrman. LoL. tightgtp, you said something above, "the thought came to me today today that how can you have closed center pilot joysticks and an open center control". Then you asked, "how can i ever build pressure in the pilot circuit". You just answered your first question yourself. The term "center" in referring to valves means when the valve is centered, no function is being actuated. Open center simply means that when supply oil enters the valve, and it's centered, the oil simply flows through the valve back to tank. Closed center is the opposite, when supply enters the valve, it's closed to tank, it's a hyd dead end. That's how you develop pressure in the pilot circuit. Flow from steering and work equipment circuits reaches the dead end at the joystick pilot valve, and pressure develops. It would build pressure until something blows or stalls if it were unregulated. That's where the pressure regulator comes into play. Once pressure in the circuit reaches a desired set amount, the regulator controls that pressure. Your first question, how can pilot joysticks be closed center and control valve be open center? It's simple. The pilot part of the control valve is seperate from the delivery part of the control valve. Again, I don't know this machine, but I'd be willing to bet it works not much different than excavator controls. When you move the joystick lever to operate a function, it's sends pilot pressure oil on a line to the spool of the control valve. That pressure against one end of the spool causes it to shift, which delivers oil out of one of the ports to do work. That's all the pilot pressure does, move the control valve spools. This is all very simple, as alrman asked, when you disconnect the pilot line coming from the regulator, and connect that line directly to a gauge, do you get pressure? At this point, we don't care how you get it, whether normal operation, or dead heading steering, we just want to see pressure. If you get pressure, then reconnect the line to the joystick pilot valve, it should work. If not, it sounds like you may have a problem with pilot valve. Also, it won't work to block the tank port of the pilot valve. When you operate the joystick, as I mentioned earlier, it delivers pressure to push the control valve spool. Well, there's oil on the opposite end of spool. When the spool shifts, the oil on the opposite end has to go somewhere, so it's vented back to tank. When you block the tank port on the pilot valve, that blocks the oil coming from shifting control valve spool, so spool cannot react and move.
ATCO - you deserve some kind of prize for that novel ! :notworthy Just wanted to clarify - pressure at the line to pilot valves has to be there as long as the engine is running, as it should get pressure from loader section of pump - if no pressure, problem exists in pressure reducing valve or shuttle valves. It has got me stumped why it loader doesn't react when pressure is delivered from steering relief....... I feel your pain tightgtp :Banghead
LoL...aww, somtimes I get a wild hair and type all manner of BS. That's correct about the work equipment pump delivering pressure to the pilot circuit during normal operation. I just suggested blocking that supply earlier to simplify things, as we are certain we can apply pressure to the regulating valve by dead heading steering and popping steer relief, that means we know pressure is againt regulating valve at that point, and shuttle check valves are now out of the troubleshooting process.
maybe some help I feel the your pain also-first I'm not a heavy equipment mechanic-I'm an industrial mechanic and a hydraulic tech. Mobile circuits are somewhat different but the physics is the same regardless of the prime mover. Looking at the flow chart some one posted-if your accumulator has a drain or a relief in parallel(most all industrial accumulators are set up this way) and the drain or relief has opened you could lose your pilot pressure via this path back to tank. If it was possible I'd take a direct operated valve(log splitter type) and connect to a function and see if either the lift or tilt would work correctly. This would tell you whether the main pump was good. a schematic would be most helpful. Hope some of this helps, Tom
ok so i was finally successful yesterday. after i changed the bad check valves, which were completely disintegrated, i still could not get the hydraulics to work. so at that point i swapped the main relief in the control valve with a known good one. still i could not get the unit to work, so i put the old one back in. at that point i replaced the hydraulic pump. then the headaches began. after all the troubleshooting i came back to the relief valve, come to find out the plunger inside had gotten chewed up and there wasn't much left. so the combination of the check valves and the hyd pump going bad took out the relief valve. so after flushing as much of the system as i could and replacing the relief valve and all is well again.
Glad you got your problem resolved-where in Illinois are you located? Tom
near rockford
Not that it makes any difference I thought you might be from southern IL, I'm from far western KY but have been gone for several years. Glad you got your problem taken care of, don't envy the mobile hydraulic tech's job-much easier to diagnose and repair industrial hydraulics. Tom