Hello all I have a Michigan 175-A from the 60s Running well Repacked boom cylinders last year. lifts and curls like a beast but…. I have drift Even when running. The boom will slowly lower And if I park it and leave the bucket tilted so the rain won’t fill it it will be flat next morn. How do I diagnose bypassing in the valve? And if I found it how would I go about rebuilding it as I’m not sure who to ask for parts. or is it just trying to find another newer model that works well a better option Many thanks in advance Tarik
Realistically, how big a problem is it? and how likely do you think it is you'll improve it? how far are you willing to go to fix it maybe? The working bits of the valve rely on a very small metal to metal clearance, so that part is not fixable except by replacing the valve. There are probably? circuit relief valves on some of the valves, but possibly not the boom lift because that is the main function so it is sized to the main relief valve. I'll guess there are no load check valves on that beast. You could study a little bit of hydraulics generally and you'll be able to identify the valve components in your valve stack, that will tell you what could be leaking that would possibly be fixable. The circuit relief could be fixable if it is on that circuit.
Thanks Delmer, Guess it’s not end of world problems but I have been lifting a bunch of thinks where I tie them to the bucket etc so I have to hurry a bit with the drift. But again it’s not end of days stuff. if the relief valves were not working properly would the pump overload tje. Before a heavy load was able to lift? It can lift a lot , I imagine that means yhe releif valves are fine? I was thinking the valve would have packings that could be replaced like a cylinder
Just a guess, but I wager a machine of that vintage those valves spools for lift and tilt have moved in and out for soooooooo many cycles that the tolerance between valve spool and valve body bore are now way out of spec and causing internal leakage, only way to fix that is valve replacement, which asks the question is there a replacement out there for a machine that old? As Delmer asked, how big of a problem is it?
Nope, valve spools don't have "packing" for internals, just precision ground fit. Yes, there could be port reliefs, but again, that's a really old valve. I don't know that there's a replacement for those valve parts.
Thanks willie I think you two have given me the info I needed. I will keep on using it as it is and not sweat the valve tolerance issue unless I find a used valve that is know you be in better shape. many thanks fellas ! Cheers Tarik
The port relief could be fixed, no fixing the main valve spool, replacement only. It's possible to make another valve work if you want to do that. You can test by plumbing in a suitable valve to the base of each cylinder, then shut them both off with the boom off the ground and come back the next day. If both cylinders are still tight and the boom hasn't dropped, then they're both good. If one isn't carrying weight, or the boom has dropped, they're both leaking and no valve will fix it completely.
Thanks Delmer, I fully understand what you are saying about testing the cylinders with shut off valves. I am a bit fuzzy on the port relief tho... If the relief valves were faulty or leaky would then not hinder the ability for the loader to put enough pressure to the cylinders to lift propery? is the only way to test them to replace them?
Do you have the list of what those parts are? 17-19 is the main relief valve adjustment. I haven't seen a valve quite like this so can't tell exactly what 9 is supposed to do. A leaky relief valve will not noticeably affect the operation, because it's only leaking down as fast as it does when off. So if the boom drops an inch per minute when off you'll notice it, but if it drops an inch per minute while you're operating, you won't notice it as much.
It drops probably about an inch per minute while operating, and drops slower while turned off. or at least thats what it seems to be. I havent actually timed it but I can if it helps diagnose where the leak is
#9 is a check valve plunger, so it seems like they built in a load check of sorts. That is a metal to metal contact seal, so it could be fixed if that's where the leak is. As opposed to the spool which is metal to metal with clearance, and you can't fix the clearance without making the spool bigger or the hole smaller. I can't be sure from looking at that, how the check valve plunger seals with the spool seal. Looks like the spool will always leak even if the check is tight, but that would defeat the purpose of putting a check valve there. If you have access, neither of those look hard to get out, and they're not complicated like an injection pump or something. Inspect that bevel and seat on #9 and report back if you feel like it?
Can't say for sure but item 9 looks like they might be port reliefs built into the internals of the valve spools. But again, according to the parts list they're not sold separately, neither is the valve spool, would require valve replacement. But as Delmer suggested it's worth taking it apart, you might find you have a broken spring for that check valve poppet which would cause a problem for sure. The spool on the bottom in the illustration looks to be the loader arm spool as it has the detent for float position.