Hanmey Backhoe Boom Lift Problem - Suggestions please!

[Bullstrode35]

I've got a Hanmey Backhoe (BHUS-225, PTO driven) that's lost lifting power in the boom and would very much appreciate some advice please.

I've done all the usual things - changed the oil, left the boom hanging (it did), checked the O-rings on the spool (no leaks). To confirm, I'm talking about the boom arm, the lower one that takes the most load and so could be the first to feel a problem. It seems likely it's the pump or the relief valve but I can't put a pressure gauge on because all the hose fittings are flat-face metric 20 which the local suppliers around here don't stock. Does anybody know of a supplier in the USA which has a good range of flat-faced metric fittings and connections that I could contact? Malone Speciality don't seem to have what I need.

While I'm at it, the pressure relief valve looks like it's received some attention by the previous owner. It's that small pile of nuts on the right of the photo. I think it's a spring & ball type but have no maker's diagram to confirm. Does anybody know how it works and if it just screws back after cleaning or do I need a gauge to reset it? So far, I've been inclined to play safe and leave it untouched.

Any suggestions or advice please on fittings suppliers and on how the valve works?

 

[Rebeldad1]

cant you swap lines with a different vale to check it?

 

[Bullstrode35]

Thanks for your suggestion Rebeldad1, much appreciated.

I took your advice and tried swapping the lines today. Not much difference in performance - still a slow and juddery boom - which tends to suggest it's a general pressure problem.

I found a different type of metric male end (measures 18mm OD) to the valves on the block as compared to the input (18 mm OD flat face); but still haven't tracked down a suitable adapter to add a pressure gauge. The search continues ...