Case/Davis trencher backhoe

[Eugen]

I used 1/2" schedule 40 steel pipe for my loader build. 5000psi rating is good enough for me. Of couse on the high pressure side I also used high spec carbon steel fittings, rated for 4000 psi. On the return side I just used standard cast iron npt fittings. 300psi is plenty strong enough for the return lines.

Bob

Elbow fittings for turns or you bent them with your strong thumb?

[thebuildist]

I used 1/2" schedule 40 steel pipe for my loader build. 5000psi rating is good enough for me. Of couse on the high pressure side I also used high spec carbon steel fittings, rated for 4000 psi. On the return side I just used standard cast iron npt fittings. 300psi is plenty strong enough for the return lines.

Bob

Elbow fittings for turns or you bent them with your strong thumb?

[Eugen]

It wasn't easy but the swing cylinder is out. What I find surprising about this backhoe is that the exterior shape of all parts is extremely bad, lots of pretty deep rust. Yet the clearest and cleanest red hydraulic oil came out of the hoses and cylinders. No sludge in the swing cylinder either. This is a bit of silver lining and gives me some hope that the pump is still ok.

[Eugen]

The side with the internal valve didn't want to come off easy. Had to pry it open using the loader.

Again, totally clean inside.

Now that the wiper and seal are out, they need to be measured and sizes figured out on the hercules site.

Although I wonder if there are any parts inside the valve that need to be refreshed.

[JSinMO]

It wasn't easy but the swing cylinder is out. What I find surprising about this backhoe is that the exterior shape of all parts is extremely bad, lots of pretty deep rust. Yet the clearest and cleanest red hydraulic oil came out of the hoses and cylinders. No sludge in the swing cylinder either. This is a bit of silver lining and gives me some hope that the pump is still ok.


EECBBA3B-753B-489F-84C0-016F3F2F303B.jpeg

That is kind of curious. Makes me wonder how long it’s been sitting?

[Spike188]

@Eugen I have a faint memory of pulling the valves out of the swing cylinder but can not find pictures to confirm their function or components.

[thebuildist]

It wasn't easy but the swing cylinder is out. What I find surprising about this backhoe is that the exterior shape of all parts is extremely bad, lots of pretty deep rust. Yet the clearest and cleanest red hydraulic oil came out of the hoses and cylinders. No sludge in the swing cylinder either. This is a bit of silver lining and gives me some hope that the pump is still ok.


EECBBA3B-753B-489F-84C0-016F3F2F303B.jpeg

It looks like you're really doing a great job with this!

It's a bit down the road for me yet, but I'll have to decide how aggressively to pursue overhauling my hoe. I can see that it needs new hoses. But if it looks fairly clean inside the hose ports, I'm tempted to just put new hoses on it, try to cycle it all through its paces using either compressed air or disposable oil, and just see how it runs.

But time will tell.

Bob

[JSinMO]

@thebuildist I don’t see why you couldn’t cycle it. I think oil would be better than air for the seals.
In my case I put the hoe to work after sitting for a decade and it functions fine, but as time goes on I’m getting more leaks and seepage around the old seals.
Just my opinions and thoughts for whatever they’re worth!

[Eugen]

@Eugen I have a faint memory of pulling the valves out of the swing cylinder but can not find pictures to confirm their function or components.

I don't seem to have the right tool to take those valves off, looks like a big flat screwdriver with a missing "wide tooth" in the middle. There is an o-ring in each, but I'm tempted to leave it as is for now.

@thebuildist , I'm with Jeff on this one, I don't think compressed air would tell you anything. From what I've seen so far on the big backhoe and the loader, they all had and still have some really really old hoses, some of them even with heavily cracked outer shell and exposed steel mesh. Yet they don't leak. Seals and o-rings on the other hand, that's where it's more likely to have leaks. If I were you I'd just hook it up and take it through its paces. I personally use the cheapest 15w40 diesel oil for the hydraulics, so if it got dirty I'd just flush it and put new one. But if you think the backhoe has contaminated oil it's quite some work to get it out, because I think you would need to do it cylinder by cylinder.

In my case, seeing the rough shape of the exterior I thought it must be awful on the inside and decided to do a complete overhaul. Now, after seeing the old seals, I think it might have been just fine for a while. But I'm not sorry doing it, it'll be more reliable once finished.

[Spike188]

My method of D100 testing with the original oil included installing a 5 micron oil filter in the two return lines between the hoe and the tractor. The quantity of filth found in the D100 during rebuild, scared me. The 646 had a brand new pump and rebuilt hydraulic system on it. Not wanting to risk damage to the tractors hydraulics, the tractor oil and filter was changed after testing. In part because of diluting the tractor oil with oil of unknown age. Filtering can not rejuvenate old oil that has been burnt.

Over the years, doing industrial equipment repair, there have been many instances of spool valve failure on machines due to lack of oil changes. It is good practice to change oil and filters within several hours after breaking in any newly rebuilt machine.

One customer had me reuse his old oil after a rebuild on a mechanical geared shear. A week later, the internal linkage bound because of the filth. It blew a peice of the clutch casting off and knocked the side out of the gearbox. That mistake cost him over $20,000.00 to repair.