Boom Pressure on JW3 BH

heartservant · Jun 26, 2007

Does anyone have any idea what would cause the boom to get sluggish when it gets hot? It has had this pressure problem for awhile and seems to be getting worst. When it is cold it is slow to raise, but about 30 mins into work it will slow down and sometimes it will not hardly do anything.

Some info: I have changed the control value, was told it would fix the problem (heck it was free, just my labor). Now when I changed the values out, I placed the value next to each other and as I pulled off each connectors, I placed it back in the same hole that it came out of on the new one. I also numbered the lines to insure that they did not get crossed.

Did not change anything. Without the boom it does not have the pressure to dig. Dipper stick and bucket works fine. I was going to take hyd line off at the cylinder and run it to see how much comes out, but I do not know which is the inlet and which is the outlet. Decided against that idea though, might be too messy.

I posted this on another site as I need all the help that I can. My dealer is hard to get any help from. WOW 2 year warrenty and sometimes I think it is only as good as the paper it is writen on. ,,,,James

RonMar · Jun 27, 2007

This is for raising and lowering the boom? Does it happen in both directions, boom up and down? It could be you have a piston seal problem(fluid just flowing by the seal and not performing any work) in the boom cylinder. It could also possibly be a problem with one of the lines to the cylinder, but your observation of it getting worse with use(fluid warming/thinning) would tend to make me think it is a piston seal. Is it activating the safety in the system when this happens? If so, it could be a line restriction or a hose lining collapse or a mechanical restriction or bind in the boom mechanism itself overloading the hydraulics. If something was binding that bad, I would think you would have other noises to indicate it or see stuff bending/straining.

Here are two things you could try to determine what the actual problem is.
1. One is to set the backhoe boom down solid on the ground(dipper vertical so bucket won't slide) and make sure there is no pressure on the system. Remove the hoses from the boom cylinder and secure them into a bucket and test the flow from them when you start up the system. IE, how much fluid goes into the bucket from each hose with a 5 or 10 second valve activation(should be about the same from both hoses). Since you don't have anything to compare to as far as flow, you may have to do this for another cylinder such as the dipper cylinder to compare available flow reaching the cylinder. If the flow is comparable between two different cylinders, then the piston seal is probably the issue. make sure the engine/pump RPM is the same for all tests.

2. On the control valve, swap the lines running to the boom cylinder with another cylinders lines. IE, swap the boom up/down function with the dipper function. If the dipper valve controls the boom properly, and the boom valve dosn't work well on the dipper, then the boom valve is the problem. If the boom still malfunctions when fed with the known good dipper valve then the boom cylinder(or hoses) are the problem.

Good Luck

heartservant · Jun 27, 2007

Boom only has a problem when it is coming up. I guess that is when it has the most weight. I left the boom in the air w/ dipper stick extended and bucket extended (@45%) kept checking on it and it might have moved an inch in an hour. I guess the boom cylinder is holding pressure.

Did talk to the mechanic that works on it for warrenty and he said that the pump is the problem. Thought he replaced it but said he didn't. OF COURSE he tell me that what warrenty I had, just expired. Was for two years or half cost of tractor (14000.00 is what I paid for it w/ FEL & BH) which ever came first. Dealer I bought it from, well let just say, worthless.

I will try you other ideas and see what happens before I pay 150.00 for new pump. ,,,,James

Bob Rooks · Jun 27, 2007

I have an LW-6 BH. Had the same symptoms. It got progressively worse until the boom wouldn't even lift it's own weight. Dissasembly of the boom cylinder revealed badly blown piston cup seals.

heartservant · Jun 27, 2007

That just about discribes mine. Is it possible to rebuild the cylinder at home? and if so who would have a rebuild kit? ,,,James

RonMar · Jun 28, 2007

I would say that if it was the pump, you would have the problem on other circuits when you put them under load. Here is where a pressure gauge "T"d into the valve supply line might come in handy for troubleshooting.

My vote is still on the piston seal in the cylinder. As with all things of mass, it takes far more energy to move or stop it from moving than it does to just hold it there. It might only leak down real slow just setting there. I would guess that if you extend the boom and dipper a bit and drove around and applied a little motion to the backhoe from the tractor movement, the added loads from the tractor up and down movement as it rolls over uneven ground, would cause the boom to start to sag as fluid squirts by the seal.

You should be able to get new seals. Replacing them will be a bit messy and you may need to get some tools to do it(seal/ring compressor to squeeze new seals down enough to re-insert into cylinder) depending on the cylinder, but these can sometimes be improvised with a little thought. you could probably also replace the whole cylinder. Less messy, but far more expensive. Either way, this is something I would definitly want to prove is the problem before I jumped into.

Good luck

Bob Rooks · Jun 28, 2007

heartservant said:
That just about discribes mine. Is it possible to rebuild the cylinder at home? and if so who would have a rebuild kit? ,,,James

I rebuilt my cylinder on the tailgate of my pickup (piece of cake, will take an hour out of your day), but be aware there are two types of cilinders (the piston seals may be the same though); on one type the end screws on, and the other type has depressed lock rings. I bought mine from Keno Tractors in Oregon because they are closer, but you can try Circle G. They have a lot of BH parts.

heartservant · Jul 4, 2007

Well finally was able to swap lines. At first there was so much pressure on the boom cylinder, when I lowered it it just fell to the ground. When I raised it it came up faster than it ever has. I thought that it was not the problem. When out to do some digging and it worked better. After about 20 mins, it finally started doing the same thing as before. Would not raise at ALL. Had to use the pressure of the dipper lifting off the ground to raise the boom. But O boy when you go to lower the boom you have to ease the stick a little or it will go crashing to the ground. I guess this means it is the boom cylinder (seals allowing fluid to bypass). If I am not correct please let me know because I will order a rebuild kit from Circle G tomorrow. ,,,,James

RonMar · Jul 4, 2007

Yep, if you swapped hydraulic circuits and the problem didn't move(stayed with boom with different supply), then the problem lies with the boom cylinder, probably a bad seal.