Ive just bought a case 680e mid 70s an got it to the shop to service it an while running it noticed the hydraulic tank building air pressure so hooked up the air tank to shop air an run off shop air with unit off to see it it still would build pressure an it does what would cause the air to leak in the hydraulic tank
Welcome tomHEF, ncdmax ! The hydraulic system is designed to maintain 15psi minimum air pressure at all times. Look under the hood, next to the hydraulic tank you will find an air line with a manual pressure regulator and pressure gauge.
Thanks an I seen that a bit ago but the cap on top the tank should it be releasing pressure there
Pressurized hydraulic tanks are fairly common on machinery, it both provides positive pressure feeding oil to the pump(s) to help prevent pump cavitation and also helps prevent ingress of water/dirt into the system like a vented system has a propensity to do
Ok so it pushing out the cap is nothing to worry about then
Tighten the cap, or it's the wrong cap. Should not leak out.
It is a problem actually. The leak causes the air compressor to run unnecessarily and it introduces excessive humid air into a sealed system. There is supposed to be an "O" ring sealing the cap. Case part #A7552. The hydraulic system oil filter is inside of the tank, in case you didn't know.
I haven't looked in it yet I did tighten the cap but it still leaks out around it