Hydraulic Over Pressure Pump Protection Question

[RickB]

It's not about how the backhoe valve is fed, it's about how oil returns from the valve. Spool seals for many don't like pressure spikes in the return circuit, much less sustained high pressure.

 

[LD1]

It would take at least a couple hours of running that way to even cause some damage to the pump. As the OP explained, he quickly found out about the issue, plus that system runs at 140 bar and the pump is rated for over 200 bar or something along those lines.

As far as the valve, it kind of hit or miss whether it can handle it or not. On my homemade backhoe, the backhoe valve is being feed through the Tank port of the drive motor valve ever since I put the machine together and it has easily over 900 hours. I do have a main relief valve right after the pump and yes, I know it's not the right way to do it but it just works anyway. So far I've had absolutely 0 issues with the cheapest valves one can buy on the market.

Whether it takes a couple of hours or a couple of minutes...Im pretty confident its still what happened.

The sympoms of the loader not working are a result of either the pump being trashed or the fact that the backhoe valve finally blew and now there was no oil in the system. Prior to this....other than a noticeable load on the engine which the OP admits he isnt that familiar with the tractor after only 10 hrs, every thing would have been working fine. The only thing that was "noticed" right away was complete hydraulic failure after it was too late. But the coupler could have popped off long before that