K guys I have a 110 loader. When u try to pick up the main boom it won't lift. But if u hold the main lift lever and hold the grapel lever over relief the boom will lift. What do u think is the prob. valve or cyl
probably relief valve problems
Another thing to check is the linkage
On your valves/levers, too much slop and you loose effective stroke on your valve. Relief valve is a good place to start.
And the relief valve is in the valve bank?? Do I pull the spool ??sorry new to this old stuff
35 yrs ago i had a G that would leak down that was the spool leaking past the valve body. so i swaped hoses so that valve worked the bucket rotate. also had a 110 that has a tandem pump with a mid section in the valve bank. so one pump section works the main boom and bucket close. other pump runs swing and stick boom ect. there will be 2 main relifes could be dirt under the ball broken or weak spring. dirt under the circuit relife or load check . a pressure guadge and flow meter would be a big help
Be quick and easy to eliminate a packing issue. Just disconnect the non pressure side hose and see if the piston is bypassing.
I thougt maybe when you ran another function it used another section of the pump providing more oil to overcome a sloppy packing.
Maybe
Well I changed hoses around. All the other funcutions work fine. Iam guessing its the packing in the cyl
Hey guys. I have a older 120 prentice crane. I just got done setting up on an omder dt 466. For my firewood processor. Hydraulics are very weak any ideas what it could be. I'm new to the forum and new to having a crane. Any info would be great thanks
Very basic but have you changed the filter and checked the suction pipe?
I'm sure someone more knowledgeable will be along
Get a helper to run it while you use a breaker bar to touch parts and listen by putting the handle to your ear.
Listen at the pump and at the valve, especially anywhere there is a large hex plug, acorn nut or allen plug because the relief valves are under.
The pump could be shot, but more likely is the relief valve in the valve spool gang is bypassing oil back to tank. It needs to seal that passage off for work to be done by the cylinder. You will hear a whine, squeel, bubbles etc wherever the fluid is not doing work. And itll read hotter than other parts of the system with a temp gun.
Fix that and you should get your pressure back. Weak hydraulics is always insufficient fluid pressure in the system. The cause of which can vary.
I'd start with a gauge installed and stall it out against relief and see what it makes for pressure. If low adjust the relief tighter and see if the pressure climbs, if so keep adjusting to being the pressure up to spec. If adjusting the relief has no real effect on the pressure readings then I'd suspect the pump.
Or the relief valves are shot
I havent had one i couldnt rehab yet. Cartridge reliefs are almost like a mechanical fuel injector.
Rust on the seats of mushroom poppets gave me the most challenge so far, and the solution was to walk a pipe tap into back of the poppet body until it grabbed then spin the poppet in the seat with lapping compound and a drill. Ive had some so pitted from sitting dry that i had to grind a new face on the mushroom and use a countersink to recut the seat, then lap.
Poof.. Right up to operating pressure. Old scrap can often be brought back to life with very simple actions. Hydraulics is one place that great stuff gets mislabeled junk by owners who dont get it or dont want to pay a guy who does.
Quote from: mike_belben on May 08, 2021, 11:10:50 AM
I havent had one i couldnt rehab yet.
Poof.. Right up to operating pressure. Old scrap can often be brought back to life with very simple actions. Hydraulics is one place that great stuff gets mislabeled junk by owners who dont get it or dont want to pay a guy who does.
Preach! Maybe I should thank the people who give it up, how else can you buy grossly undervalued equipment.
I'll second what Chevy said. Could be simple inexpensive fix. Also worth while to leave a pressure gage installed.
I did on my "antique" Gafner to stay in reasonable working loads on the old girl.
Ah Mike,I wish I had you around to do some tinkerin' for a bit😊 On my ol' Pettibone skidder the reliefs won't hold much pressure for the blade or the steering ( blade can't lift the machine and the steering relief squeals if you're not moving, I've never put a guage on it) I've adjusted them both ways with not much improvement.
Just shootin from the hip here. If the reliefs are physically in good shape and numerous fuctions are weak it points to excess clearance probably in both the pump housing and in the spool valve bores themselves.
Something to always keep in mind when troubleshooting is the simple concept that pumps only make flow. Resistance to flow makes pressure, like your thumb over a garden hose turns the psi in that hose from 1 or 2 psi to 60.
The pressure rise is the actual muscle of hydraulics.. More psi more force. The gpm is the speed.
If a blade moves fast but is weak it suggests flow is sufficient, pressure is not. If youre hydraulics can make your motor lug down, pressure is there. Low pressure equal no lug, no smoke, no governor kicking in to bring it up etc.
Fast leakdown when turned off points to sloppy spool valves. The main relief cartridges are outside of the picture when it comes to holding a load up. The valve spool is what is supposed to keep the cylinder full so if its not look there.
Newer closed center, compensating and hydrostatic systems add a ton of complication but old open center is pretty straight forward and backyard serviceable.
Warning, don't raise the relief valve pressure on the old Prentiss loaders, they break just fine with the factory setting.