I'm working on a Hitachi:shf EX 100 - 5E. The owner called me out because the machine had boom issues. He would release the joystick and the boom would continue to raise. Long story short, after all pilot issues were found to be normal I opened up the boom valve section to find a bad spool and badly scarred sleeve. I pulled the valve stack and sent it out to be re-worked. The sleeve was oversized and a new larger spool was chromed and ground to fit. I have it all back together and the boom, along with all other functions work great . . . . . except the swing brake. Swing either way and stop on a hillside of any type and the boom heads whatever direction gravity wants it to. Push the pilot lever forward and the brake sets. There is a square cartridge manifold mounted to the side of the swing motor which I assume to be the control valves for the brake. There are two pilot hoses coming from the top of this manifold. One goes to a port in the end of the valve stack, the other to a solenoid valve mounted adjacent to the valve stack. I tee'd a gauge into each of those two lines and found that the line coming from the valve stack has full pilot pressure whenever the pilot lever is accuated. Is this right? It seems I should only see pilot pressure there when the swing valve is shifted. Any chance a plug was left out somewhere inside the valve stack when the work was done? I have years of hydraulic experience but this is a machine I'm not that familiar with . . . it's gray market . . . and I don't have a manual. Any help would sure be appreciated.
Swing brakes are set up to release whenever a piloted function is operated. It doesn't set again until all functions have been released for approximately seven seconds. I don't recall a manual switch to release the swing brake on a Hitachi but I could be wrong. You might also check to see if pilot pressure goes away after so many seconds without operating anything. The other item to consider is where did the metal that damaged the boom valve come from? It is not uncommon to have a swing motor break up inside and put metal all over the system. I would suggest pulling the return filter and seeing if and how much metal is in there. The swing motor is easy to remove and tear down with a little care. A few hoses and two bolts will allow you to get the thing out. Good Luck!
the part you are reffering is a swing dampener valve. this part regulates the swing brake to prevent jerking or swing brake control regulator so the upper structure would not stop abruptly. (soft swing stop)
Update Thanks for your input guys. Here's a little more info. The swing motor and gear seem to be fine. The machine has never had a swing issue and the swing braking is a new problem. The machine still swings uphill or down either direction smoothly and quietly. I realize failures can cause damage to other components downstream. The lines were flushed and the hydraulic reservoir was thoroughly cleaned. The screen was cleaned and a flushing filter installed. All I found in the return filter was a small amount of O-ring material . . . origin unknown. There wasn't any metal. I can now track onto a small slope and extend the boom uphill and let go of all functions . . . the boom immediately starts to drift downhill. If I shut off the pilot safety lever in the cab the swing brake sets. As soon as I re-engage the pilot the swing brake releases again, even with no functions being operated. Boy would I love to hear that there was a manual switch somewhere to turn off the swing brake and that it had been inadvertantly toggled! Not so lucky I'm afraid.
the swing brake of the machine is compose of 2 fuction. 1. swing brake in the swing dampener valve. 2. swing lock. swing lock function after 7 seconds without swing pilot command. the problem i see in your case is you have a internal spool leak or pilot pressure leak on you swing stick. hope this helps
Update I just got off the phone with the shop that repaired the valve. Sounds like the constant pilot pressure in the line with the gauge SHOULD be there. I'm heading back out to the machine to do more testing. Thanks rgl726 for the schematics. That always helps!
It looks like the pilot line coming from this valve should be the switching signal for the swing and track brakes. It seems like neither is working. The solenoids have full voltage any time the key is on. The strange thing is that nothing changes even with the solenoids unplugged. I've tested the solenoids and they are pulling in. I inspected the spools that are actuated by the solenoids and they look good . . . . no broken springs, bad lands etc. Not sure why I have a pilot signal all the time. This project is killing me and the local Hitachi dealer won't help at all since it's a gray iron machine.
The problem valve This is the valve that seems to be delivering a pilot signal when it shouldn't. We had the lines removed from this valve when we removed the machine's main valve stack. We color coded all the lines and took good pictures so we know nothing got hooked up in the wrong place.
Have you checked if one of those coils has power on it at all times and shouldn't? Also, did the hyd shop remove those coils from the manifold? I seem to remember some gizmos in there that can easily be dropped. Just a few thoughts.
Thanks ATCO Actually that solenoid valve assembly just bolts to the main valve stack with 2 bolts. I removed the lines (all color tagged and photographed first) and just unbolted this valve, capped the ports and zip tied it out of the way. The main valve stack was where the original problem was. (bad boom spool) In trying to troubleshoot this pilot issue I did pull those coils just yesterday to inspect everything. Tha coils seem to work fine and the spools, springs, and washers in behind them are all in good shape. Not having a flow schematic for this machine (gray iron) is making me crazy. I went back to the machine this afternoon and did a little more testing. I'm pretty well convinced that my original incilation was right. I think the line coming from the valve stack should be the pilot switching signal for the swing brake, not the line from the solenoid valve. I may need to pull the cover off that valve bank in the morning. In talking to the hydraulic shop it sounds like there's a small spool in behind that port . . . . . maybe it's stuck or has debris holding it open. This is turning into a humbling project!
I might be wrong.NA not me. I used to del.parts at Hitachi dealer in Houston.I think the mechanics said that Grey market was the same as ours just no pollution controls and safety features.Foreign Country's don't believe in safety it's to expensive.
One thing to remember is that Hitachi supplies power to most solenoids and controls the ground via the computer. The 2 pilot lines to the swing are one constant pilot pressure and the other is a signal line to a spool to open up to allow the constant pilot to release the swing brake. The brake that is coming on is only a park brake and not meant to stop the motion of swinging. Someone explained that there is a 7 second delay after letting go of the joysticks. 4 seconds is what I was taught. When you operate any upper function except travel the swing park brake comes off. Now you mention that it will drift on a side hill. That braking would be done by the spool in the valve bank not allowing oil back to tank and the crossline reliefs allowing oil to go from one side to the other. When you put the lever up that is allowing the park brake to come on. this is hard on the frictions of the brake. Now to relay throw a wrench into it. Grey market from Japan, the swing brake should be the same as North America it was more pump control that could be different on a Dash 5 machine. European versions quite often do actually have a park brake switch. Still read about what I said about park brake and swing braking.
Just had a look at the pictures again, those coils only line up and operate the port directly in front of it. In this case PH and PE. The rest of the valve is more of a pilot manifold. So coming off this manifold you should get your pilot pressure that is constantly to the valve. PG is the hose. SH comes out of your valve bank and is the signal to release the park brake. Any function except travel.
Uh OH That would make perfect sense, except for this; the swing spool is a motor spool so A, B and T are common . . . . only P would be blocked. Right? If it I can't imagine 2 cross port reliefs going bad all at once and this happens in both directions. Even so, why would I ALWAYS have full pilot pressure coming out of the port on the valve bank. There's no dropoff after 7 seconds. The pressure is there any time the pilot lever is turned on in the cab.
Whoa...clarify that. Pilot lever? Did you mean to say...safety lever?
Safety lever works . . . . it shuts off all pilot functions for "safety's sake"
I thought someone would bring that up. Just because it is a motor does not mean its a "motor spool". The A and B are blocked in neutral on this machine. This is your braking. You definitley have a problem with pilot oil constantly on to the signal of the swing motor brake when you lower the pilot neutralizer. I don't want to say it but I am suspecting some spool problems like the wrong one in the wrong hole. The pilot oil goes into the valve bank through an orifice (To maintain pilot oil throughout the rest of the system) Then the oil goes through all upper function spools and back to tank. So when you activate an upper function the oil gets blocked from going to tank and builds up to the pilot pressure. This pressure does 2 things, it activates the upper function pressure sensor (used for auto idle). And it goes to the swing motor and releases the swing brake.
Thanks KenAl I spoke to the rebuilder again and it sounds like there are a couple very small spools in a block at the A & B ports fro the swing. I'm headed back to the machine to see if one of these has hung open as they may send pilot pressure internally to the signal port. The rebuilder did say that the swing circuit in this machine was a motor spool center. Now you have me curious.
Just put your gauge in line like you had it and block the hose off it. Now you can check to see if you are getting signal pressure from the valve bank or somehow from the swing motor?????? Sounds like you are getting different info from them and me so I will let you deal with them. Good luck
Which company rebuilt your valve?
Thanks everyone. Looks like there is an issue with the valve bank after the rework. Everything else has been ruled out. The rebuilder has been stand up about this and is doing what they can to help out. I've had work done by these guys for years with good results so I hate to give them any bad press here. The valve is coming out and headed back to them within the next couple days. Hopefully we'll have success after they take another look. On to the next project for now.
I have a problem in Tata Hitachi EX1200 excavator with swing operation problem. When I operate swing, it swings and as soon as I stop the operation it keeps on drifting smoothly and then stops with vibration and abnormal sound. Please help me out.