The best after you repair/replace the pump is to put a direct acting relief valve tee’d into the pressure line coming directly out of the pump and run the discharge hose from relief valve to an empty clean 5 gal bucket. Preset the relief valve using another hydraulic source about 100 psi over your tractor max psi specs. While you are doing your scouting adventure to troubleshoot your current issue downstream you won’t have to worry about ruining another pump, the excess oil will dump into the clean bucket with no harm and you can filter the oil and reuse it.
If you don’t do this you run the chance of blowing up another pump
Yep. That's exactly what I would do. How to do it needs some details to flesh it out for hydraulically challenged, but if you can replace the pump you can definitely add a relief valve. Once you do that, you can trouble shoot the rest of the system at your leisure because you know that the new pump is protected. Plus you can ask to get any needed advice right here. This works so easily because almost all of these basic open center hydraulic systems on compact/utility tractors are the same (except some JDs). The pressure pump is brand specific only because of the mounting configuration, but the insides of the pump are similar. And after the pump the rest of the system tend to be so similar that they can use interchangeable parts.
For that matter, a person can simply plumb in a PTO-driven hydraulic high pressure pump on any tractor. Those used to be popular back when tractors didn't come with pumps mounted on the engine. Some attachments use them today instead of using rear remote hydraulic outlets driven by an engine mounted pump.
There is no downside to adding another relief valve. It's like having a belt and suspenders. You can buy a relief valve online from several sources for under $100. Surplus Center.com, Summit Hydrauics, or Zoro. I would get one with the proper threads or adapters so that it can simply be threaded on inline in series between the pump high pressure outlet and where ever that line goes first. No cutting involved. Go overboard for another thirty bucks and add a 5000 psi glycerin-filled pressure gauge while you are at it. More fun than a TV. The relief valve itself should be pre-set for whatever pressure you decide you want to limit your system to..... or you can do it just as wdchyd said in post #6 above. Setting a relief valve takes less than ten minutes with one wrench and one screwdriver. I tend to run less pressure instead of more, so I set mine at 2500 psi on my YM336D. The relief valve will also need a return line capable of handling the flow. You can run that low pressure return ine down to a "Y" into the existing return line.
Do you have a loader on it? If so, post some photos of the control assembly and we can get more specific.
BTW, every loader control valve I've ever used has a relief valve built into is so that most plumbing errors won't break the high pressure pump. Weird that yours did that. There is also a relief valve in the 3 pt system. The most common error that will break the pump is trying to add a loader to a system
without understanding the hydraulics in the loader control valve and using the wrong power beyond adapter plug. That error will blow a high pressure pump up sometimes. But putting an additional relief valve as described above so that it is between the pump oulet and the input to the control valve will protect even from that error.
Good luck with it,
rScotty
