Case D100 Backhoe weak

[shaunm]

Hi,

I am new to the forum, I live in South Africa and recently attached a D100 backhoe to my Same Tractor.

I have a problem with my Case D100 backhoe:

The backhoe is hooked up to a tractor with a flow of 20gpm. The front loader and
power steering running of the same pump work fine. The backhoe seems very weak.
I have adjusted the relief valves to within factory spec, the main releif being 2000psi
and the Boom and Dipper being 3500psi. i have adjusted a little further and the relief
on the tractor itself starts releasing.

I have checked for air and leaks in the system, replaced a few bent metal pipes.
Overall the backhoe seems weak. The only other noticeable problem could be a small
dent in the metal pipe going into the Dipper Cylinder. The cylinders themselves don't
leak any oil, the Boom does drop down by itself after a few minutes. Could the cylinders
need rebuilding ?

Is there any else i could check/diagnose ?

Many Thanks
Shaun.

 

[BukitCase]

Shaun, wecome to TBN - I think you already diagnosed your problem - if you have pressure and flow, and the boom leaks down, and there's no oil leaks EXTERNAL, then either it's a weak backhoe by design (doubt that) or you have an INTERNAL leak - this could be either control valves or cylinder pistons (packing rings).

One way to find out WHICH is the problem would be to temporarily plumb in a high pressure shutoff valve between the control valve and the side of the cylinder that gets pressurized to LIFT the boom - then raise the boom high, shut the new valve so oil can't escape the cylinder when the boom tries to drop, and see what happens.

If the boom still drops, it's the cylinder packing - if not, it's the control valve... Steve

 

[shaunm]

Thanks Steve, I tried putting a shutoff valve in and the boom stays solidly up. It looks like it is the spool valves, i will take them apart today and replace O rings and anything else i can find. Thanks once again for that valuable tip. Shaun.