Hello, I've recently purchased what appeares to be a mf50a and managed to get a service manual. here is the deal. Front end loader works fine and barly even affects idle of engine. switch to backhoe and nothing works well. It boggs the engine bad on all functions in one dirrection but will stall engine while barely moving components in the other dirrection. there are 6 levers on the cesna valve body and the "good" dirrection is not the same for all valves. Initially I didn't notice the difference in dirrection and thought that there was a flow restriction in the outlet hose. The hoe had this problem before it was purchased by the guy who sold it to the dealer I got it from so history is pretty much non existant. I did remove the exhaust hose and it " looks" ok. I can see through it. I also looked through the hose from loader spools power beyond fitting to hoe spools and it looks the same. two other observations. in the manual. the diagrams all show two outlets from the FEL spool. on to hoe spools, and one to reservoir. (with no coresponding pictures) I only have the one outlet. Secondly If I lift the hoe boom first then try some other function, the hoe boom dropps a small bit each time I actuate the other lever and the engine boggs down. Oh yeah and one other thing, the functions that work "better" are not those favored by gravity in all cases. thankyou for all your insights.
Is the "good direction" consistently either extending or retracting the cylinder in question? What does the hydraulic plumbing look like on your machine. Pump to hoe valve, to backhoe valve, to reservoir?
the "good" direction moves from 1/4 to 1/2 of cylinder length before bogging down and lugging the engine. whereas the bad direction only moves a cylinder 1/2 to 1 inch. and has a more dramatic effect on engine rpm etc. like the pump is dead heading. No reliefs are letting the pressure go. On the plumming, it goes from reservoir and cooler via a T to pump. Then to two spool valve for FEL. This valve body has a power beyond fitting with a hose that feeds the valve body on the hoe. The return from there goes to a T fitting wich sends oil to reservoir and cooler. Thanks for asking. I've been poking around here for a week and see A LOT of knowledge! I've already made leaps and bounds in understading this machine. but I haven't seen any problem described that sounded quit like this one! I hope I just missed it and it's simple as pie. thanks again gdkm
I'm going to have to think about this one a little bit. That part seems real odd, I'd think about disconnecting the two hoses going to one cylinder and connect them together, bypassing the cylinder and see if the valve does the same thing. But give it some time, somebody will have seen this before...
Thanks for your thoughts Delmer. I just lost my over wordy next question ( UGH) but I'll try again. I'm thinking there might be at least two separate issues here. One.... a flow restriction that over loads the spool valve assembly. and two..... unequal venting from A &B in the spools. it occured to me, that the "diference" A vs B could be an amplification of a problem or even normal condition that might be a non issue without the restricted flow issue. So, before I put my feed and vent hoses back on .... , or un necessarily buy new ones. Do you or anyone else here think I can safely rule out a delamination type blockage in either or both of those? ..... Is it even possible in a hose that size? I think the ID is over 1/2 inch. ???? I hope otherwise the fellow whose seen this before, sees this thread ! thanks again gdkm
These "feed and vent" hoses, are these the supply hose from the loader valve to the backhoe valve, and the hose from the backhoe valve back to the reservoir? With the plumbing run the way you describe I can't see how they could cause this problem on the backhoe but NOT on the loader, the oil flows through the same lines all the time. "the "diference" A vs B could be an amplification of a problem" That's why I asked if the good direction was extending and bad was retracting the cylinder (or vice versa) or if each function is random? Do the cylinders ALL push out the rod easier than they pull the rod in? With the engine off, do all six of the valves operate the same with the same range of travel, and the same spring feel in both directions? With the engine running, does it make a difference if you "feather the controls" or pull the lever all the way immediately. Do the cylinders move without a load and then load up suddenly? or do they load up gradually? And can you move the cylinders the full stroke, how?
I would take the lines from one cylinder at a time and check for proper port hook up at the backhoe control valve. Trace the two lines from the boom cylinder back to the valve and make sure those to hoses are correct with that spool. Then do the dipper/stick the same way, and on to the bucket lines. If the machine has a extenda -hoe make sure that function is in neutral also, along with all spool heights the same in neutral for the control valve.
Since I can't come up with a reasonable explanation, I keep having this vision (nightmare?) of a red plastic plug pop into my head...
First, on Delmers red plug thingy. I realy think that, or some eqivalent of it, would be the most sensible explenation. But I just haven't taken enough apart yet to find "it". Until I get farther, ..... going back to many questions in Delmers post before that. On the feed hose and return hose, yes Those to and from hoe spool assembly. that is, after loader spool. As to why the loader could work but not the hoe, I had asked myself that, and, I thought (perhaps foolishly) that regarding the post hoe spool return line. it could have the inner lining diturbed by venting the hoe spool, but the venting from the loader would be bufferd by the hoe spool and another 6 ft of hose before it and would not make the same surge of fluid. so ok that may be "crazy think", here is more, as for the hose between the two spool assemblies, when the loader actuates, it works as a vent. When the hoe actuates it works as a feed, and maybey the lining only colapsed under the higher pressure when the hose was acting as a feed. So... I hoped perhaps this would leave the possiblity open that I just need a hose. Yeah probably just wishfull thinking. and lots of it. Anyhow it seems a red plug issue would also have to block the loader as well as the hoe. wich brings me to this question.... Can a single spool or cylinder restriction (or leak) cause back pressure on all the others? That woul be a revelation! I'd certainly need to change my aproach. As to feathering the valves. yes, it makes a difference. without that, I couldn't move things in the "bad" dirrection at all. The individual spools each seem to my feel so far to have about the same travel from neutral as each other in both dirrections, and they all seem to have about the same feel. Ill go over this again as soon as I get out there again. as for extension vs retraction on the cylinders I'll have to go look at the machine again tommorow to make sure. but I think that is yes, the cylinders all seem to extend better than retract. the only way to get all the way in either dirrection is feathering on off on off on off etc. after initial point of pressure build up is reached. One other observation on this point is that when I take stuff apart and loose oil from the valve body the first lever pull/push or two after restart work a bit better. then once a load builds up it stays. Lastly, on sheepfoots suggestion. I can only think, that if any hoses were crossed, at least one or more control positions would either do nothing, or at least partially do somthing other than comanded. either opposite dirrection of component. or move a different component altogether? feel free to tell me that any or all of my logic here is just nutty. I'm just trying to sort out as much as possible before I end up with the whole machine in little zip lock baggies. thank you so much for helping me ramble through this. I'm not trying to be stubborn on my own thoughts here either just wanted to put out there what I had thought about it before proceeding. on the hose delamination thing. I had heard the blockage could be "only under load" is this true? and can it happen in a hose with a 1/2 inch plus ID? with an open center system such as this, does the return line flow more when everything is in neutral or when there is a spool in the circuit before it actuating a load? Thank you for putting up with all this and trying to help me. gdkm
I'm by no means an expert when it comes to hydraulics,, but this is what I'm thinking, think of a circle, " O " now in this circle, fluid starts at one end and continues to flow to the other end, constantly....on the front half of the circle, you have your "loader spool" that intercepts flow to your loader when needed, whats not used is returned to the circle. Your loader seems to be doing fine in this setup...now on the rear end of the circle, you have your "backhoe spool",when this is put into play, "your engine bogs" and hardly any movement is done,! this would tell me the problem is in the spool, either its not returning fluid to the circle or the return line on "that" spool is defective. As for the spool, could also be a stuck relief valve on one of the controls, has anyone changed this spool to "close center".... whatever it is, it appears that "one" thing in that spool is restricting return flow...I would concentrate on that, but thats just me.
"does the return line flow more when everything is in neutral or when there is a spool in the circuit before it actuating a load?" The return line has the whole flow in neutral. The cylinder rod side has a smaller volume than the side without the rod, so the return is smaller when the rod is extending, and larger when the rod is retracting. That "intensifying" affect is what is/could be causing the good side/bad side. That is, restricting the return from the hoe valve bank to the reservoir. It's possible for hoses to collapse, I have no experience with that (even online ) and I don't think the problem is upstream of the hoe valve bank. "Can a single spool or cylinder restriction (or leak) cause back pressure on all the others?" A cylinder will not, they would ALL have to be extremely rusted up internally for the problem to be the cylinders. A single spool should not affect the others, BUT the valve bank functions as a whole, there are parallel connections running the length of the valve bank, a red pipe plug in the wrong place... The parts book shows two different hoe valves. Does your "end cap" on the hoe valve bank have a hex plug facing forward and backward, in addition to the return line fitting? Take those off CAREFULLY and examine for red plastic etc.
That's really really helpful stuff. I may be starting to understand a smidge now. On Delmers suggestion with those two hex plugs. I do have those. and I did have them off already. Three times. once "hey whats in here?" twice "are these the same?", and "can I get the innards out?" " not in any obvious way" and third time " since I can only get the springs out and my book implieis they are the same (though they don't look like it) what happens if I switch the springs? ....darn still no change" . New question can I get those innards out without pulling the end cap or shooting pieces through adjacent buildings? oh and I promise to put the springs back when I put my hoses back on. thanks again gdkm
If you didn't lose the springs yet you're on the right track. I can't say how they come out exactly, but here's what I'd try. Pull them out backwards with: hook scribe, needle nose, straight pin "snap ring" pliers. All on the inside of the spool where the spring rested, don't scratch the bore of the valve body. When that fails, try a pin punch and see if you can GENTLY tap the whole works out the other side. If the red plastic is compressed where suspected, it will be in the way, at least in one direction so try both directions before resorting to the next step. You do have the diagrams on page 36 and 46 that show what you're trying to get out, right?
I have a service manual not a parts book so the page numbers don't jive, but I do have what apears to be an " acceptable" diagram. It even shows it apart, but doesn't seem to explain how it got that way.
correction to my previous post. there is a paragraph on disasembly, but it implies there is something that can be "hooked" on the "replenishing spools" but I only see a flat surface at the bottom of a round hole. also I didn't leave the springs out. just switched sides .
when I had the rearward cap off at one point, I tried a magnet to pull on the spool, but it only moved about 1/2 inch. I stopped cause I didn't know what was holding it.
took those apart again, and looked closer. these " spools" are hollow and those springs sit inside them. the side hole is part of the spool. hook rotate pull out.! long forcepts in grab plunger, pull, sticky but.... out. repeat other side. all apart. found.... nothing. :-( . a bit of rust on one plunger, and one plunger oring looking tired but not ripped. next?
Can you see clear through the hole from one end to the other? On one of the pages there's one "cylinder" in the middle with a set of spring,spool etc on each side. Most likely that comes out either end and then you can see through. Then reassemble only the two caps with their sealing washers and start it up to see what happens. With any luck the junk gets pushed into the return and ends up in the reservoir, where it will do no harm, except depriving us of any satisfaction.
I may not have the satisfaction of ever seeing what was in there, BUT it would be pretty hard to beat the satisfaction of seeing that hoe work. and without a a penny in parts. DELMER! Thankyou soooo much! Now I just have to figure out what else to do so I don't wreck it on its maiden voyage.
So it works? Did you put the parts back in again now?
yep! I put the parts back in and it's all good. well actually The stabilizers still seem to strain more than I would think they should when raising. but tollerable. the rest moves real good.
A little other contribution for consideration of all concerned. I mentiioned earlier that the diagram in my book showed two vents from the two spool loader control. ( horizontal cessna ) and I could only find the one. That, suplied the pressure to the hoe spool assembly. well apparently that is NOT the vent for the loader! The loader spool assembly apears to have a port where it attaches to the loader frame so it can vent dirrectly to the reservoir just under the filler cap! that could really have thrown a person off track.