Tube Frame hydraulic lift system.

Doing a bit of cleanup today on the pump and cylinder. The tag on the pump unit is quite faded and all I can read are Made In USA and numbers 15A75 and 44175. I surmise those are the model and serial numbers. Definitely some spots of black paint over top of cordovan brown paint that has orange paint underneath that and appears to have been put over bare metal with no primer. I have lots of sanding to do. I found that the control valve that I am pointing to has a spring return to center action going counterclockwise but does not going clockwise from center. This is the first one of these units I have ever owned or had my hands on so I'm not sure if that is correct
or not. Seems like it ought to return to center by spring action from both directions? I will try and do a bit of research later and maybe figure it out. I do remember that the unit seemed to work with the cylinder extending and retracting when I tried it on the tractor it was removed from.

Ok, thank you both for the info! I saved the pdf link for the hydraulic lift manual. I will surmise I have the first version as the ram is the smaller diameter piston rod [1/2"] and the pump mounting bolts etc. most closely resemble the early version. I see the spring item #54 in the diagram. I will also surmise like stated, it must be broken. Time for a disassembly and inspection. I might have gotten a bit ahead of myself this afternoon. I got out the air and electric tools and ground, sanded, and buffed most of the parts clean for a coat of primer. Still have hardware and some small parts yet to do. I found a stress crack in the pump mounting bracket after I got the paint and rust sanded off. Cracked right at one of the four holes where the pump bolts on. I wonder if that was caused by whatever broke one of the original support bars? I Veed the crack both sides, welded and ground it smooth. Did lots of work with a cupped wire brush on a grinder and sanding discs with the small angle grinder on the two mounting brackets. There is quite a bit of pitting on the bracket the cylinder bolts to and a bit here and there on everything else, so I used the rust converter type primer on what I had ready. That should deal with any traces of rust lurking in the pitted areas. It was just warm enough today that I was able to open the garage doors while I was priming. The fumes drifted away and didn't stay inside. So, I will probably give pump and cylinder a coat of color next to seal the primer. After working on them they can be wiped clean, scuffed and painted again. The two hoses are junk for sure.

Well, I have been a bit sidetracked by some suddenly needed maintenance on my pick-em-up truck. 2012 Sierra with 72K on the meter. Last Saturday I heard a grumble in the left front and it was getting progressively louder before I made it back to home base. Truck is in the garage up on jackstands getting both front hub-bearing assemblies along with new brakes on all four corners. The rotors, pads had a few miles left in them still, but the rear shoes were getting close to used up, maybe were original ones it was born with? So, I decided to go ahead and do it all now as long as it was in the garage and I had the tools out. I would have just had to repeat part of the process later on anyway, so now was the time to deal with it. So, while waiting for some parts to come in I decided to take a look the pump unit. I gave it a coat of black color to seal the primer a few days ago. First thing as I was removing the masking tape the little tag came right off. If I had known it wasn't stuck to the pump canister very well, I would have just peeled it off before I started sanding on it. I took a bunch of time to make sure I didn't mess up the tag while I was cleaning around it. Oh well, now I can do a better job of sanding and redo the paint. No biggie. Upon removing the canister from the pump, I found that the return spring indeed was missing one of its arms. Fortunately, it looked like a clean break with only the one large piece and no small metal fragments present. Saw no signs of any damage on the broken off piece like it had got into the pump gears so that was a very good find. Have contacted Bolens Parts and Supplies about a new spring. Definitely enough pitting on the cylinder rod to cause leakage, so I will have to come up with a solution for that.

I figured out an easy solution for the pitted rod of my lift cylinder. I bought a new piston/rod end plug assembly from Bolens Parts and Supplies, along with the replacement return spring and a shaft seal for the pump unit. I was searching their site and found the new rod piston assembly listed, and on sale. So, I bought it. Problem solved. Had been cruising eBay for a good used cylinder, but none listed right now. Probably will see a couple-three pop up soon. A few suggestions had been made about getting a piece of chromed rod possibly from an old shock absorber or strut assembly and cutting and threading it to work for a replacement rod. If you could find one that was the exact diameter as what you were trying to replace, that idea would probably work quite well. Being as I have no metal lathe and would have to pay a shop to do it, I bypassed that idea for the present. So this new rod piston I have on order is the newer style thats 5/8" diameter. I have the original cylinder that was on my H14 tractor with the same size rod, but was pitted and seeping oil. I had replaced that cylinder last Fall with a good used cylinder I found on eBay. I decided to disassemble both cylinders and see what the differences are between the older style 1/2" rod type and the newer 5/8" rod type. I used 2 pieces of hardwood board to clamp the rods in the vise very tightly and using a short punch that fit the bore of the clevis I was able to rap that with a small hammer and break the threads loose. It's a right-hand thread so I went lefty-loosie and the clevis screwed right off. I wasn't sure exactly what method to try to unthread the pistons from the rods without marring them. I'm thinking that the pistons could be held tight between the hard wood boards and the old rods gripped with Vise-grips or a small pipe wrench to unthread them. It would ruin the rods but they are rust pitted and not serviceable still anyway. Kind of a so-what deal I guess. It appears that the pistons, cylinders, end plug with the mounting lug and the clevis are the same for both versions of the cylinder. The 5/8" rod is necked down and has the same thread size on the ends as the 1/2" rod. And the end plugs where the rod comes through are sized for the respective diameter rod the cylinder used naturally. I cut a slot in a piece of 3/8" diameter rod I happen to have lying close by and then cut a strip of Scotch-Brite pad to fashion a polishing tool of sorts. I ran it with a drill and it polished up the bore of the cylinders very nicely. The bores of both cylinders look good, but I might give the nod to the older one that originally had the 1/2" rod. The new pieces will fit right in, and I will have a newer style cylinder with 5/8" rod. Or at least that's my grand plan right now. I think it will all be good.

You mentioned that there will be a bit less power on the rod side of the piston. I surmise that that would be because of less surface area of the face of the piston that pressure will be applied to. Because of the larger diameter of the 5/8" rod. Makes sense. Just for grins I did some quick , down and dirty measuring. With the piston and 1/2" rod I get about .500 from the edge of piston to the rod and on the piston with 5/8" rod I get about .480. The ends of the 5/8" rod are tapered down and threaded the same as the 1/2" rod. I don't know if my photographic attempts show it very well though. So, there is a small difference between the two piston rod assemblies. And of course, there will be a bit less volume of oil inside the cylinder with the larger diameter rod, so I surmise that's why you say it will move faster than when under pressure from the closed end. Am I on track here? Just making some guesses based on what I think I know. Please straighten me out on this if I'm wrong!!