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Excavator hydraulic problem, help please

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Tom B (tbone)
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PostPosted: Fri Mar 30, 2007 3:49 pm    Post subject: Excavator hydraulic problem, help please Reply to specific post Reply with quote

Ok, I have a 1973 Hein-Werner C14A excavator that I got out of the woods practically for free just to mess with on the farm. I replaced one of the Denison pumps on it with a brand new one on the circuit that provides boom, bucket and one side of the tracks. With the old pump, hydraulics were very slow and weak. New pump on and there is nothing! The boom moves about a quarter inch and stops (basically takes up the slack in the bushings). It has a Husco 3 spool valve that I took out the relief valve and put new o-rings in. Still, nothing! Pump is primed. I am at my wits end. One thing I forgot to check with the relief valve out was the spring in it to see if it was broken (thats a pretty hardy spring could that rascal actually break?). So, best I can figure its either:
1) Broken relief valve spring and or faulty valve
2) Something cracked internally in the control valve housing
3) Suction line internally sucking shut (saw this in another post!)
Any other ideas???
Thanks in advance,
Tom

 
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Old Magnt
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PostPosted: Fri Mar 30, 2007 4:39 pm    Post subject: Re: Excavator hydraulic problem, help please Reply to specific post Reply with quote

Did you get the right rotation on that new pump????

 
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Tom B (tbone)
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PostPosted: Fri Mar 30, 2007 4:54 pm    Post subject: Re: Excavator hydraulic problem, help please Reply to specific post Reply with quote

Yup, its the correct pump. I actually put two pumps on. The dipper and other track drive that the other pump supplied work like a charm. Good thought, one of the first things i checked. I'm just pulling my hair out on this one.
Tom

 
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Old Magnet
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PostPosted: Fri Mar 30, 2007 5:14 pm    Post subject: Re: Excavator hydraulic problem, help please Reply to specific post Reply with quote

I'm not familiar with that machine, just going on hydraulics experience. I had a similar experience with an old Case hoe. Turns out there was a perforated screen in the control valve that was full of junk because the return oil filter cartridge was missing. Cylinders would barely move until the system was cleaned up. Lost some hair on that one too...LOL.

 
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Tom B (tbone)
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PostPosted: Fri Mar 30, 2007 5:25 pm    Post subject: Re: Excavator hydraulic problem, help please Reply to specific post Reply with quote

I wish the control valve had a screen that could be plugged. I bought a single spool husco valve just like one thats on the machine off ebay for a couple bucks so I could have something to take apart and examine its innerds. Taking the control valve off this machine would be a monumental task and i am trying to avoid it especially if its not necessary. I keep wondering if it could be the suction tube from the tank. It may make sense that with the old pump, it did not have enough suction to fully close it off and now with the new one it sucks it completely closed. I have drained that darn tank twice, not looking forward to doing it again but it beats taking the valve off. Thanks for your thoughts and welcome any others.
Tom

 
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NC wayne
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PostPosted: Fri Mar 30, 2007 5:53 pm    Post subject: Re: Excavator hydraulic problem, help please Reply to specific post Reply with quote

The best thing you can do when dealing with hydraulics is to use a flow meter with a load valve to allow you to "see" what's really going on inside the system, otherwise your just spinning your wheels. You might be getting plenty of flow but no pressure or decent pressure but not enough flow to even make up system losses. If the boom hydraulics are moving a little but not enough tio actually pick the boom I'd say you've got a relief stuck somewhere. I'm not familiar with that particular machine but most hydraulic machines I've dealt with have both a main relief on each individual pump as well as a port relief on each function. Are you sure you replaced the orings on the main relief and not just one of the port reliefs? If it was just one function off that pump that was bad I'd lean toward a bad port relief but since you indicate that all functions fed by that pump are effected the it just about has to be the main. I answer to your question, yes the main relief springs can and do break, as well as just getting weak. I don't know how yours are but some reliefs are set using shims behind the spring. When you took the relief out could you have unintentionally dropped some or all of the shims? Often a few thousands worth of shims can make alot of difference in the relief pressure and even a few hundered pounds can make the difference of the boom raising or not. If the suction line were sucking shut to the degree the pump wasn't putting out the pump ought to be cavitating bad enough to create enough noise that you'd know what was happening there so I doubt that's your problem. Many machines also have a suction screen inside the tank but it would create basically the same symtoms as a line sucking shut if it wer clogged so I doubt that's a problem. If it were me I'd flow check the system to start with but lacking a flow meter I'd at least tee into a couple of lines and see what's going on pressure wise... Good luck and let us know what you find.

 
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Tom B (tbone)
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PostPosted: Fri Mar 30, 2007 6:26 pm    Post subject: Re: Excavator hydraulic problem, help please Reply to specific post Reply with quote

I have a flow meter. The thread size on it is 1" and the outlet hose from the pump is 1 1/4". It also has a max reading of 30 GPM and the pump is rated at 35 GPM. I did not know if it would restrict the flow too much so I was looking for a bigger one. I replaced the main relief orings as well as all the in line relief valve orings. Most of the lines go along to a block where there is a relief valve in it. I am not knowledgeable enough to know why some line have those relief valves while others do not but I did put new orings/backup rings in the in line ones. There are no shims in the relief valve. It is basically a long tube with holes that has a metal valve in it like a plumb bob(has an oring/backup ring) that is relieved by a spring controlled valve(another oring/backup ring) that is adjustable with a screw. There are no suction screens (would have been a good idea) on this particular machine, I have the parts manual. I did crack the outlet line from the pump while it was running. I expected the fluid to be under more pressure like if you cracked a water line at home. It came out, don't get me wrong just not with the force I was expecting. One thing I can add is when I tried to raise the boom, the pressure on the cracked line went up because more fluid spurted out. Also, when you move one of the conrol valves, you hear a slight groan. Its not like the sound you hear when the cylinder bottoms out and the relief valve chatters. I cannot tell where it is coming from, if I had to guess, its from the valve body.
Thanks very much for your help and please add any other thoughts.
Tom

 
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135 Fan
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PostPosted: Fri Mar 30, 2007 9:14 pm    Post subject: Re: Excavator hydraulic problem, help please Reply to specific post Reply with quote

Could it still have an air lock? Just a thought. Your flow meter should work as long as you don't run the engine full throttle. Dave

 
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mike pawlek
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PostPosted: Sat Mar 31, 2007 2:02 pm    Post subject: Re: Excavator hydraulic problem, help please Reply to specific post Reply with quote

Try swapping the working pump with the one that doesn"t work that sounds like a lot of work but it"s one way of ruling out the fact that it is not the pump.

 
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Tom B (tbone)
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PostPosted: Sat Mar 31, 2007 5:57 pm    Post subject: Re: Excavator hydraulic problem, help please Reply to specific post Reply with quote

Today I took the relief valve adjustment screw out to check if the spring was broken, no such luck. I ordered some JIC fittings to hook up the flow meter. Should have it checked in a couple days. I did think of switching the hoses between the pumps but the hose lengths would not reach. Wish me luck and I really appreciate everyone's input. This is such a great forum to figure stuff out. You guys are great!
Tom
This is a pick of the machine the day I got it out of the woods. It had a hole in a hydraulic hose so I was putting fluid in with my backhoe.

 

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original possum
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PostPosted: Sat Mar 31, 2007 8:28 pm    Post subject: Re: Excavator hydraulic problem, help please Reply to specific post Reply with quote

If the cylinders have pilot valves (you will see small lines from between the ports) then you may need to bleed the lines.

 
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Dave Neubert
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PostPosted: Sun Apr 01, 2007 3:52 am    Post subject: Re: Excavator hydraulic problem, help please Reply to specific post Reply with quote

Is your controls mechainical or pilot if they are pilot see if you are getting pilot pressure there should be small lines on each end of the valve for each circut should have 200 300 psi or so when you engage that cicuit.

 
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Tom B (tbone)
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PostPosted: Sun Apr 01, 2007 5:03 pm    Post subject: Re: Excavator hydraulic problem, help please Reply to specific post Reply with quote

The controls are mechanical. I will post the results of the flow meter test in a couple days.
Thanks!
Tom

 
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Rob in Yukon
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PostPosted: Sun Apr 01, 2007 6:00 pm    Post subject: Re: Excavator hydraulic problem, help please Reply to specific post Reply with quote

Yep, hydrualics and excavators can be hard on the hair. Removing and replacing components can trigger problems in the suction side. I have only two cents to offer, but in the case of collapsed filters and junk plugging screens, usually you will have some function at an idle and lose it with rpm/demand.

 
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Tom B (tbone)
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PostPosted: Mon Apr 02, 2007 4:24 pm    Post subject: Re: Excavator hydraulic problem, help please Reply to specific post Reply with quote

I did replace the hydraulic filters, they were a mess! Thanks for the input.
Tom

 
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