Air in backhoe?

/ Air in backhoe? #1  

Joesark

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Apr 15, 2023
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13
Tractor
Mitsubishi MT2201D
I am putting a backhoe attachment on my tractor. The backhoe had tyranny fluid in it, so I cycled it out of the cylinders and then refilled them ss best I could. Blew out the lines. Now, when I hook the hydraulics up to the backhoe, not even the front end loader will work. Unhook the power line from the hoe and the loader works perfectly. Do I just need to try cycling everything for a couple of hours, or does this point to some other problem?
 
/ Air in backhoe? #2  
Did you add remotes to power the BH, or use existing? try disconnecting the BH cylinders one at a time & cycle the valve to fill the lines, then reconnect & go to next after topping off hydraulic tank.. Could be big air bubble or lack of power beyond sleeve if you tapped in to existing hydraulics.
 
/ Air in backhoe? #3  
Air in the lines and cylinders will eventually take care of itself. Revisit your plumbing/connections, explain (maybe even post some photos?) how and where you connected to the tractor hydraulics. Maybe your "nothing works" problem can be sorted out.

Just a guess, but I suspect you probably put a tee in a pressure line? That NEVER works.
 
/ Air in backhoe?
  • Thread Starter
#4  
I did tee into the pressure line. What other method is available? I'm just a carpenter who dabbles in machines.
 
/ Air in backhoe? #5  
check out summit hydraulics website. They have schematics for adding remotes (& other stuff) & parts needed. Usually, you take the last hydraulic valve in your set-up, plumb into the power beyond port, then tee into the tank return line. Basically, you run everything in series.
 
/ Air in backhoe? #6  
You need your pressure flow through all valves plumbed in series (no tee), preferably in power beyond configuration. It's not all that complicated but it's not like 2 X 4's. You can't just nail things on wherever it's convenient.

Maybe do a little research on open center hydraulics, series plumbed control valves.

Again, some photos will help identify what you have and what you need.
 
/ Air in backhoe?
  • Thread Starter
#7  
Here's the valve body. Power comes in on the right. Which is the power beyond port?
 

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/ Air in backhoe? #8  
I can't tell enough from that photo. The pressure in port is USUALLY on the left, the same side as the relief valve. I don't see a relief valve in the photo. The power beyond sleeve should be on the opposite side, and will screw into one of the out ports, sometimes labeled N, but not always. Can depend on the make of the valve. As I see it now you have no operational power beyond right now. There should be three lines, not two, connecting the valve to the tractor hydraulics.

So what are you trying to accomplish, and how are you doing it? Show some photos of where on the tractor the lines on this valve are hooked up when the hydraulics (loader and three point) are working. Show us what you are trying to tie into this, and how are you doing that? Where are the lines you added, where do(did) they go?
 
/ Air in backhoe? #9  
Almost every hydraulic control is in series, from pump to power port (P) on first control valve, out of power beyond (PB) and in to "P" on next control valve and out at PB port into next "P" port and out "PB" to next "P" port and so on... Does not matter if you have 1 or 2 control valves or 10.... Its almost always a series arrangement in a open center system.... And if connected correctly system should be self purging of air after a few valve/ram cycles....
 
/ Air in backhoe? #10  
Here's the valve body. Power comes in on the right. Which is the power beyond port?
Look at valve body closely it may have a "P" designation on one port for Power in and a "PB" designation for Power Beyond for out port, and possible a "T" port for tank (design dependent) ...
 
/ Air in backhoe? #11  
Almost every hydraulic control is in series, from pump to power port (P) on first control valve, out of power beyond (PB) and in to "P" on next control valve and out at PB port into next "P" port and out "PB" to next "P" port and so on... Does not matter if you have 1 or 2 control valves or 10.... Its almost always a series arrangement in a open center system.... And if connected correctly system should be self purging of air after a few valve/ram cycles....
Exactly, but he's not there yet, and on his own he's not likely to get there soon.
 
/ Air in backhoe?
  • Thread Starter
#12  
Harry, you are absolutely right; I run mainly on enthusiasm and ignorance. I really appreciate all the coaching. Can't send pics now because I'm at work, but I'll get some this evening. It makes sense now that the left side would be the pressure side. In theory, would I be able to hook the right hose to the inlet of the hoe and then hook up the return from the hoe to the reservoir?
 
/ Air in backhoe? #13  
Well, sort of. The power beyond will usually be in one of the ports on the right side of the valve. There are often two or three ports there, only one will accept the sleeve. From there to the backhoe valve, and back to the tractor. Exactly WHERE on the tractor depends on whether or not anything is needed downstream from the hoe. If your hoe is three point mounted, and you need to lift it for mobility, then the hoe valve stack should also be plumbed with power beyond. If the three point is not to be used, then the hoe return can go straight to sump.

You might read through this, it will give you some idea of why all this is necessary. It's all second nature to me, since I deal with it on a regular basis, but often people can be confused with it all.

 
/ Air in backhoe?
  • Thread Starter
#14  
Well, it's starting to make sense! I hooked it all up the "sort of" way and ran it at an idle long enough to make sure all of the functions work properly. I have it unhooked now so I won't be tempted to actually dig with it. Is there any special power beyond valve I need, or is it just whatever fits on the loader valve? I have a picture of the downstream side of the valve; which port is most likely to be the one I use?
Thanks!
 

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/ Air in backhoe? #15  


It looks like you have a P40 valve. Is that what's on the I.D. tag? I've used a number of them. If it's an older valve it will have #10 ORB pressure and return ports. If so it will take the 220 915 sleeve. Newer valves have moved over to BSPP ports now and will take the 220 842 sleeve. It will go int the port marked N. From there a line to the backhoe valve.

That's your starting point
 
/ Air in backhoe?
  • Thread Starter
#16  
I don't see anything like p40. The number on the tag starts with a k. Not finding any other markings.
 
/ Air in backhoe? #18  
Air in the lines and cylinders will eventually take care of itself. Revisit your plumbing/connections, explain (maybe even post some photos?) how and where you connected to the tractor hydraulics. Maybe your "nothing works" problem can be sorted out.

Just a guess, but I suspect you probably put a tee in a pressure line? That NEVER works.
that is a helluva guess:)
 
/ Air in backhoe? #19  
that is a helluva guess (A Tee in the Pressure Line) :)
Putting a Tee into the pressure line is a pretty basic mistake. I think we've all done it. Doesn't work.
What happens is that the hydrualic fluid just takes the path of least resistance - which in this case is whichever return line looks most favorable. The fluid returns back to the sump, and never gets around to doing any work.

There is a trick for making Tee connection in a pressure line - and I'm sure that Harry knows this one too. It was commonly done on old Massey Fergusons from the 40s and 50s when people wanted to run a loader and still have 3pt capability.

The trick is that instead of a Tee, you use a manual hydraulic selector valve. The manual selector valve has a hand lever on it that will only let you send pressure to one system at a time.

Here's how it works on a tractor: Most people mount the selector valve on the dash for convenience. You can turn the lever on the selector valve one way to pressurize the 3pt system, raise us the implement, close off the 3pt hold-in-place valve (usually between your feet) and now the 3pt implement is held up & out of the way.
So you reach forward and switch the selector valve over to pressurize the loader and you can use the front end loader for as long as you like....or until you need to shift back to the 3pt. ....and repeat.....

This constant switching can be quite a circus given an old Massy with a pathetic 3 gal/minute hydraullic flow and leaky hydraulics at both ends. But it works. And lots of old farm tractors were rigged that way. It's cheap and easy and any front end loader is a wonderful thing.

I mention it not because it is the best way to do it, but because so many were done that way.
The path that Harry has you on to use the power beyond port is much, much better.

Oh, and DO NOT use plumbing fittings. Use hydraulic fittings. Plumbing fittings will break and spray.

rScotty
 
/ Air in backhoe? #20  
I don't see anything like p40. The number on the tag starts with a k. Not finding any other markings.
Well, my eyesight "ain't what it used to be" no argument there, but name on the tag looks like it says Chief. If you pull the plug from the port marked N and look inside I'm betting you find the counter bore machined in to it. If the plug is an ORB #10 thread, I would order the 220 915 sleeve and try it. If I'm wrong you're only out the postage to return it.
 
 

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