If I ever wanted to rebuild my hyd pump......JD500

In the end, after some advice from this forum, I went the right way, what you do if you want to know what is actually happening in your hyd system. is to isolate the system from the pump.

T a line into the pump outlet (before the main releif valve) feed that output to an inline pressure guage, then in series to an inline releif valve (set the releif valve low and put the dump port directly into the resevoir, put an adjustable flow control on the out side of the releif valve (I used a ball valve with a handle, ideally you want a flow meter, but I wasn"t concerned with flow just pressure and the flow meter is quite expensive) then out of the adjustable flow control and back in to the pipe that was originally hooked to the pump.

Fire the machine up make sure your new test relief valve is set to low. Set your idle to about 1000 rpm (typical) then start to slowly choke the flow off from the system with the flow control and watch your pressure guage. your new test relief valve will begin to dump to tank at the low pressure leve that you have set it to.

It made me feel a little less nervous to leave the flow control slightly open, even though I had the releif valve there, it made me nervous during the test to have the full pump pressure choked right off... once you start to see the pressure build on you test guage, you can then start to adjust your test releif valve "releif pressure" "UP" to see what your pump is delivering, OBVIOUSLY DON"T exceed the pressure level specified in your book. You could hurt a pump. When you feel comfortable, then choke the flow control fully closed and see what pressure your pump is putting out.

Here is my point, after spending so so much effort chasing a mystical loss of pressure all around the valving and releifs etc etc, I found it was my pump at fault, this is the only way to go and then you know, I wish I had done it from the start.

I got a quote from JCB on the pump, they wanted $3500, I bought one from a company called White House Hydraulics in the UK BRAND NEW with Warranty and had it shipped to my door in 3 days for about $1000.... I"m installing it now.

Mike

PLUS if your housing walls are scored, wihich they likely are if any bearings are gone, you will not have the 100% output.

I don't know much about piston pumps, it is a piston pump?.... but it's all mechanics, if you have a book, take it apart and replace the worn parts follow the book, but I would consider the rip off price of parts and start shopping on the web. BUY NEW, especially with a pump unless you have pressure AND Flow guarantee., to me a used pump is like a used comdom, not that I have ever had to use a used condom, but you know...

What I found in buying the pump was to go to the manufacturer of the pump and buy it through their distributor NOT the backhoe manufacturer, google the pump part number or "pump for ..." or start checking with White house hydraulics, the most expensive part of my endevour was the shipping from the UK but even that was not too bad for a 85 lb pump ... like $350 pump was like $800 plus tax and duty. You'll find a US supplier or distributor..

Mike