Shermanbackhoe

Hello guys, I really enjoy reading discussion forum and jokes. I have a Sherman backhoe mounted on a 801 ford powermaster diesel. It used to operated fairly good, but got to where it barely moves and I noticed that the hydraulic looks real foamy in the resivor after running it. A lot of the hyd cylinders leak and a lot of the hyd hoses need to be replaced. Is it worth repairing or just scrapping? Larry fm mo.

Like I always said about mine,"It beats the he11 out of a shovel"!

Absolutely worth repairing. The foam is likely air, as atleast the three main cylinders are double acting. This means that if you have a leak, not only does hydraulic leak out, but when the cylinder retracts, it creates a vacuum. Unless a ram is bent, you can usually clean and polish the ram and replace the seal. Because the major cylinders are double acting, I would not recommend using soapy water to find the leaks on the cylinders. You should be able to see the leaks. When you replace the seals, remember that you will need to prefill the lines and cylinder to minimize air in the system.

Pre-fill the lines and cylinders? You've got to be kidding! On almost all hyd. systems all you need to do is make sure the reservoir is full and work the system several times to get the air out. You may have to add some more oil or in the odd case loosen a fitting to relief an air lock but pre-filling the lines and cylinders, how do you even do that without most of it leaking back out?

Air or any gas, compresses, and is bad to have in a hyrdaulic system. For a small system, such as a small backhoe, I would put the hose fittings to the cylinders on loosely, start at one end of the first cylinder (the side of the cylinder where the piston is), with the pump operating start sending fluid thru the line, until you have a solid air free hydraulic fluid and tighten the fitting. If you are starting with one of the double acting, which the major ones are, apply enough pressure to move the ram to the other end of the cylinder, and repeat for that end of that cylinder. Do this for each cylinder that has been removed from the system. The remaining air will be very little which should easily cycle thru. I've done some big system where you tighten one end of the hose and start pouring hydraulic fluid into the other end.

Hydraulic, I don't want to disrespect you. You appear reasonably intelligent. I have to ask if your experience is mostly cranes. They have axial piston hydraulic motors, which are variable displacement, which means that when you hook everything up tight, like you mention, you run the pump with the swash plate at zero displacement, all the air is cycled right to the res. The only way I've a hydraulic cylinder not need either bleeding or prefilling if it has had the ram cleaned and polished and the seal changed is if it's a single acting, fully retracted and has a perfect unobstrcted supply of fluid, such as a house jack or an engine crane cylinder.

I have rebuilt hundreds of cylinders from huge excavators to lawn mowers and have yet to have to bleed a cylinder and most have been running for years. I have had to bleed the suction line of axial piston pumps to prime them. Rebuilt all three boom cylinders on a JD backhoe this past week, cycled all of them twice and put it to work. Granted filling cylinders and hoses may be the "proper" way, I'll bet that few are done that way. JMO

Listen to Hydraulics and Dave, Huntress is full of chit.

Scrap heck no. Now is it worth fixing well that depends. As for a hose needing replace if it leaks yes if it does not why fix something that is not broken. I have part of an old Sherman back hoe and I will not scrap if because it has parts some one can use.
By the way where in MO are you I am at the Lake of the Ozarks

seals and hoses are easily replaced, its worth fixin :wink:

i think to get air its got to be sucking air in the suction line or around a loose fitting etc.
never bleed hyd system yet . it will work its way out .

To all the great people who gave me feedback on the backhoe. THANKS. Old, I'm originally from the bootheel ( Kennett, cotton country), but I live in Wentzville now. Is the crappie biting yet at the lake, my freezer is empty. Getting back to the backhoe, I guess the first place to start is rebuilding the hyd cyclinders with new seals since they are leaking bad. Also what would you use to polish cyclinders? Do the pistons come out easily and where would be the best place to find new seals? THANKS again. Larry frm MO

Idb, Here are three links
http://www.fluidpowersafety.com/fpsi_alert-05.html
http://www.precisionfluidpower.com/cylinders.htm

http://www.maintenanceresources.com/referencelibrary/ezine/caseyhyd2.html

The first two show a conflicting tale regarding manually removing air from the cylinder. I was always taught that cylinders must be pre filled, manually bled etc to remove air, which is the first link showing the hazards of using a cycling the double acting cylinders to remove air. It has become second nature, and I can safely say that the US Navy, the US Coast Guard, Waste Management do not allow cycling the cylinder to remove air. To the credit of my critics, however, I must cede that Precision Fluid Power list cycling as their method of removing air. Those are your first two links.

The third link is the brake down and repair procedure for cylinders. When they detail the procedure for ensuring the ram is true, it tells you to first check for a polished sign on one side of the ram. If you see the need to check for true in the ram. Everywhere I have done this the QA standard, which isn"t mentioned, is 0.002". If you have less, I have never had anyone that would not accept that as true. The link only says use fine emery cloth in a cross pattern. If you have a clean ram with only the minor scratch, I would use a 400 grit. If you have build up on the ram, and have to use a course sheet to get it to where you are at the metal expect scratches from the paper that you will be finishing with 400 grit. The rest of the third link should walk you thru the cylinder repair.

Thanks for the reply

Thanks for the reply

Bob, thanks again for your time and help with the info. There are four cyc. that are leaking. The left and right lower that lifts the rear wheels and the l and r that moves the boom side to side. All of these have a dark rust color on the rams, but they are smooth. I may have to wait a while to tackle this due to rotator culf surgery on my right shoulder,can't use it for much at this time. Larry