Jinma Backhoe Swing Cylinder Leaking

[Smalljobs]

I'm having a problem with one of the swing cylinders leaking oil. I haven't removed it yet but it squirts momentarily right out the side near the thick midsection where it's mounted. I'm wondering if there's a vent hole there and I seeing oil that made it past the piston seal. I can watch the boom swing and at just one point the oil squirts out and then it stops. I don't recall if it's when the cylinder is extending or retracting. It's hard to see and I don't want to put my head in there with boom swinging.

 

[RonMar]

Mine has vent holes on the swing cylinders. They are about 1/8" in diameter and located about where a front port would be located. I have thought about welding front ports to the cylinders so I can run them in parallel, but I just havn't found the time The problem with the vent hole is it injests dirt and will shorten the seal life. I had an end cap come unscrewed so have had them out, and I found all kinds of crap inside the front end of the cylinder... Adding front ports and crossover lines would close up the front of the cylinder, and add some swing strength to the boom...

Sounds like you have a piston seal leaking

 

[Smalljobs]

Ron - Thanks. I suspected this was the problem. When I imported the BH, I also ordered two extra repair kits for every cylinder!

 

[Bob Rooks]

Mine has vent holes on the swing cylinders. They are about 1/8" in diameter and located about where a front port would be located. I have thought about welding front ports to the cylinders so I can run them in parallel, but I just havn't found the time The problem with the vent hole is it injests dirt and will shorten the seal life. I had an end cap come unscrewed so have had them out, and I found all kinds of crap inside the front end of the cylinder... Adding front ports and crossover lines would close up the front of the cylinder, and add some swing strength to the boom...

Ron,
I think it's more involved than that. I was going to do that with my LW-6 hoe, but it was pointed out to me that I have the wrong type of cylinders to do it. The cylinders must be "balanced", that is, equal displacement on each side of the piston. As it is now, one side has a rod, the other does not. A hydraulic lock will occur in short order. A balanced cylinder wil have a rod sticking out of each end.

 

[RonMar]

How exactly will it bind/lock Bob? I don't see that happening. Right now, the supply lines go to the main chamber/piston ends of the cylinders. These lines connect to the working ports of a single dual-action spool valve, so the two cylinders work just like a dual action cylinder does.

What I am talking about is putting a "T" at the current cylinder attach point on the piston end of each cylinder. From these "T" fittings, I will run lines to the opposite cylinder rod end. IE left rear T'd to right front and right rear T'd to left front. When I give a boom right command, it sends pressure to the rear of the left cylinder to push, and at the same time to the rod end of the right cylinder to cause it to pull. The opposite ends of the cylinders are connected with a low resistance path back to the reservoir. Since the base and rod ends are connected thru a T, the fluid to the different volume cylinder ends will flow as needed thru the two branches of the T. Yes, one cylinder will have more push than the other one will have pull, but because it needs more volume, it will move at a slower rate than the one with less force... I don't see how this can bind as the opposite sides have a free return thru their T and equal but opposite plumbing... the two ends of the opposing cylinders receiving pressure will simply divide the work based on their abilities.

What I do see it doing is adding about 75% more fluid volume required for a given swing, so it should slow the boom down a fair bit(mine is too fast/twitchy now). It will also add approximatly 75% more force to the boom which will be a welcome change as I can hardly push much more than a bucket full of soil off the top of a pile now

 

[EE_Bota]

Using a Tee approach means a parallel connection, and I don't think that is a problem. The piston side will draw more fluid than it's mating rod side, but they are each free to make their own draw (get their own bite at the apple). I think the problem would happen if they were in series.

 

[Smalljobs]

I have the cylinder out and found the threaded gland retainer was finger tight. With the threaded retainer fully withdrawn I cannot seem to pull the rod out of the cylinder. It's almost there but seems to be hung up in the threaded area. Should I reconnect it to the hydraulic hose and use hydraulic pressure (and a bath) to push it out?

 

[Smalljobs]

I finally got the rod and piston out by pulling harder. Now, what's the best way to replace all these parts. I have factory repair kits.

 

[wdchyd]

Clean, polish, clean, deburr, clean, lubricate, clean, carefully reassemble with clean bench and tools, clean and test

 

[wdchyd]

Oh, don't scar the piston head under the seals with pointy sharp tools......:banghead: