I have a 76 case W20 Loader and it started building high hydraulic reservoir pressure. It builds enough that it blows the short hose off on the suction line at the hydraulic pump. I have found that someone has replaved the relief vent on the line going into the reservoir thak from the brake system with a grease zerk, so that didn't help things. But, I have been using the loader for a few months with out a problem. So something else has happened. Hope someone can give me a little insite? I'm thinking it must have something to do with that line coming from the brake system.
Your pressure protection valve stays closed untill the air pressure reaches 85 psi, then starts flowing air to the hyd tank. It will keep flowing air to the tank untill the system drops to around 65 psi, due to heavy brake use/air leak. The ppv will shut the air off once again untill air can be brought back to the 85 psi. Air pressure also runs threw the pressure reducer valve before the hyd tank which reduces it to 10+/- 5 psi inside the tank. The grease fitting needs to come out to install the releif valve so you don't over pressure the system. Need to remove the grease fitting/install air gauge and see what your pressure is in the tank/ adjust the prv to get the pressure down or replace it. Ask if you need more info.