Check Valve Issue? (JCB 1550-B)

I've had this machine for probably 20 years. When I first got it, I changed out filters. I seem to recall when I changed the hydraulic filter, there were small bits of metal in it (on the magnet). Since then, when I change it out, I've always feared more metal bits but instead, I have what I'd call small iron "filings" like dust.....which strikes me as probably more typical.

(that was just backstory)

One thing it's always done and is getting worse.... the backhoe will slowly drift to the "right" (passenger) side of the machine. If I'm going across a slope, I'll have to reach back and move the lever to keep pressure on it to prevent it from moving.

If I'm opposite, it will NOT drift to the 'drivers side' of the machine.... it only drifts one way. That can be very annoying when you're trying to be careful on your movements as now you have to keep constant pressure to negate the drift while doing whatever else you're doing.

Years ago (probably 15??) I ordered what I described as a "complete rebuild kit" from JCB. Turns out it's primarily washers as best I recall (it's STILL sitting my drawer).

I thought about finally digging into this today.... looking at their schematics and it's dawning on me.... and the point of my post.

Could it be the check valve that is (without seeing it yet) damaged, and allowing this to swing sideways? It will drift down SLOWLY, but to the right side, it's getting downright annoying as to how quickly it will drift over there.

Having ZERO experience with something like this, I'm hoping to get some ideas as to "look here first". It would appear on the schematics that the check valve is pretty easy to get to. If it's not the check valve, then I'm forced to presume part of the plunger/spool (?) is damaged. Obviously, I won't k now anything until I dig in there a bit.

Being mechanically inclined, I'm not concerned about doing this.....but, I'll still ask.... are there any certain pitfalls I should watch-out for?

I might add the swing/trunion cylinders have been rebuilt so I know they'are not the issue.

Does your hoe valve block look like this?


I’d guess it’s one of your ARVs leaking. You could try swapping top for bottom On your slew spool and see if your problem switches to the other side.

I went through something similar a while back. I think there is a common misconception as to what the check valves actually do. Don’t think that is your problem.

I've not taken anything apart but that looks similar to what my manual shows so yes. Question is this to suggest that it might be an o-ring problem?

LN Pipeline said:

You could try swapping top for bottom On your slew spool and see if your problem switches to the other side.

Click to expand...

Did you see what he typed at the bottom of the picture? One of your ARVs may be leaking internally.

Having never done it how difficult or intricate is it to dig into this.

I might add given the schematics it doesn't look difficult you just want to keep it clean

Right, those ARVs look to simply be mounted to the valve body. Clean everything real well and you may be able to carefully swap the two that affect the functions you want to correct. If problem moves with ARV, then you know that's what needs the work. The corresponding ARV may have trash caught in it or it may have worn out parts. Might end up being an inexpensive fix.

Welp, if that DOES fix it.....and I already have an entire O-ring set for the entire unit.... it could be viewed as a free fix!!

Scenario: Let's say I have a bad ARV. I guess first, I'd have to take the main cover off and look to see which one appears to be affected.... none the less.... if that happens. Would you go ahead and dig into the others since I already have the parts or just put them back in my drawer for another 5 years?!!

Also, it seems to call for a "special" spanner wrench. I've got to think I can use some other form of spanner tool....? Or, should I just shut up and order one?

If you can get to the ARVs in question easy, then I would just swap them for now and see what happens. I don't think you need a special tool to swap these. You use that spanner when you disassemble one it appears to me. It looks like unscrewing Item #1 removes the whole ARV. I'm no expert though, never owned or worked on this hoe.

Here ya go.

That was great, thank you!!

Update:

Knowing I'll be exposing the hydraulics, I spent some time today cleaning out the cab of the machine to get as much dirt out as I can.

Decided to open the ARV. As far as the metal is concerned, it was in apparent 100% good shape.

The ARV directly on the swing valve, had one of the two O-rings missing (Diagram "B", items 18/19.

So, I thought let's take a different one out....and one of the two O-rings on that one literally disentegrated in my hands.

So, clearly all of these are going to need new seals, of which I have.

That's all the further I got.... and, for the record, my intent is to pull EVERYTHING out and replace the internal seals.

That said, I'm wondering if this alone could be enough bypass to allow the bucket to swing? I'm ignorant on what parts do what so I'm clueless. In the grand scheme, it won't matter because I'll take the others apart as well, I'm just trying to learn more about what does what.

Coytee said:

I'm wondering if this alone could be enough bypass to allow the bucket to swing?

Click to expand...

Looks like those simply seal the ARV to the valve body, so my thinking is, no. Unless it was leaking outside the ARV case as the bucket moves. I would replace those bad pieces and swap the ARVs as planned and see if the bucket now drifts the other way.

After finishing work today, went out and spent maybe 30/45 minutes. Took the top three of them, pulled them off and replaced all the seals.

Fired up and lifted backhoe....and it started to swing. It's NO surprise to me that the underside (rods? whatever they're called) will need seals replaced.

Turns out there is a hard plastic 'seal' on these that is a spiral seal (think of a plastic key ring) and it's wound on. A regular seal goes next to it. On two of the three the plastic seal was totally missing and interestingly, on the third one it had two regular gaskets. So according to the diagram, it's one plastic, one rubber. If that's accurate then someone has either been in there to mess around or, the factory did it. I've NEVER had this apart until other day and now, today. (shrugs shoulders).

Still...machine is 1987 and if bottom side seals are original, it's easy to think they need replaced.

We'll see. If it doesn't rain, I HOPE to crawl under there this weekend and finish the underside.

Thought I'd report back "the rest of the story"....

Went down today to work on valve block. Figured it would take me an hour or two.

Been at it for four hours.... I'm doing it in place. My 1 1/4" socket doesn't fit the underside ARV's...they're too close to the wall. Had to loosen the mounting bolts to allow it to come out. Got the first valve unsrewed from the bottom and it just SPRUNG apart flying in different directions in the grass/leaves. Great. I can't find the bolt (turns out it landed on the "top" of the rail UNDER the machine, behind a hose.

Really????

Can't find the washer. Decided to take second one apart to discover the washer is part of the spacer so I DID have it. I lost the new replacement washer. It dropped out of my fingers, should be in a 2" area.... picked up the leaves, twigs.... it's just gone. (sigh)

Had to loosen the valves from the top, crawl under loosen things under, go back to top to pull out & replace washers. Put back in, crawl back under to tighten it up under there.

Darn it.... the spring is too tight. (light bulb of memory goes off) I bought a huge Snapon tool chest from a Klipsch head. Along with it were a bucket of tools. I seem to remember there being a valve spring compressor too......exactly what I need.

Yep....found it and got the parts back. There was more that bit me in the annkle, like a (hard) part that is oblong, fits between the very bottom cover "cup" and machine. I let it twist diagonally and put next one together.... can't put covers on so had to undo first one, rotate oblong item then put back up.

Excited....started the machine. Now, I've only done two of the four valves. The drift problem SEEMS to be cured. For the life of me, I can't figure out which one was the culprit UNLESS those ARV valves were the issue. So far, ALL of them have had messed up washers. Frankly, the washers on the valve stem itself (to my highly sophisticated & trained eye!) looked to be in place and fine.

Go figure.

Got to feed the dogs so stopped there with a smile. When I do the other side, hopefully tomorrow, that will tighten up the bucket from drooping (or so I presume as the cylinder has been rebuilt)

What an adventure. So, at the end of the day you have no drift! Sweet. Always lay down a big tarp or similar under the machine first. I prefer a large broken down cardboard box to work on myself. It can save you when stuff drops.