Jerky Boom Cylinder

[dstankus]

Hello,

Have had a problem with the boom motion of a 1969 Case 580CK backhoe that I recently bought. When the boom control lever is moved, just a little, the boom moves uncannily fast, and the engine sounds a bit strained when at a slow idle. This happens in both directions - up and down. The difference in control lever position for slow raise and fast raise is almost imperceptible. Move the lever just a little, and the boom barely moves. Move the lever just a little more, and it is at full speed. I cant seem to get the level of control I need to use the machine. All the other backhoe and loader functions are nice and smooth. RPM is about 1500. I have not yet verified that the flow restrictor (p/n D27565) is in the boom drop line, and that it is installed in the proper direction.

Any help would be appreciated - fluid level is where it should be and I am changing the hydraulic filter this afternoon just in case.

 

[RedNeckRacin]

Well, this isn't much help, but those case hoes are not known to be smooth. Have you operated other similiar vintage machines? they can be their own quirky self. If you just bought it, i would suggest a little practice and see if you can smooth it out a little bit. If nothing else, you can slow those motors down to just above an idle until you get the feel for things.

 

[J_J]

You can do a test and see just how much fluid is going to the boom cyl by removing the hoses and place in a bucket and use the valve lever to get an idea of the flow or measure the flow.

If to fast, use restrictors in the fittings or use needle valves in line to adjust the flow to your satisfaction.

You can also lower the engine rpm to reduce the GPM flow rate.

 

[dstankus]

You can do a test and see just how much fluid is going to the boom cyl by removing the hoses and place in a bucket and use the valve lever to get an idea of the flow or measure the flow.

If to fast, use restrictors in the fittings or use needle valves in line to adjust the flow to your satisfaction.

You can also lower the engine rpm to reduce the GPM flow rate.

Ok - thanks for the advice - so it sounds like you should be able to utilize the boom and dipper at the same time - and trying to use the dipper while the boom is moving should not stop the boom and vice versa. It is possible that the issue is my skill level - but I don't see how if I am holding the boom lever to a position where the boom is moving very slowly, and then if I keep that lever exactly still and then start to use the dipper, that the boom should stop moving. I will get a pressure gauge, and do some measuring -

 

[Arc weld]

The way to make a backhoe run the smoothest is to use 2 functions at the same time. The hydraulics are designed this way. The thing I find hardest to master is the swing. It takes a lot practice to be able to stop it just where you want in a fast smooth action. There could be something worn or needing repair in your valve spool if there is almost no feathering ability with the boom cylinder.

 

[dstankus]

Well it looks like the pressure is right on - measured exactly 2200 PSI at the point that the relief valve activated. I will continue to work through the manual's suggested tests with the use of my 3000psi pressure gauge. Hopefully my neighbor will have his flow meter. I will disconnect the backhoe here before too long and make sure the restrictor is in the right port of the boom. Something tells me its in the wrong port by the way its behaving.