I bought a 2005 bobcat 331g and after using it for a while the hydraulics seem a little weak. I hooked a pressure gage to the test port and raised the blade until it maxed out and read the pressure. I am getting around 2600 psi. A check of the service manual says it should be 3450. Figuring the main pressure relief valve may help fix it I tried adjusting it. It had absolutely no effect. Even screwed down to the max it never read over 2600psi. Im not sure what to do next and am hoping it isnt a pump problem as they are $4500 new. Any suggestions on what else to check or try? The only other clue is that when the blade is maxed out it starts at 2600 and slowly drifts down. Is it possible that the relief valve itself is bad? How often do pumps go bad and do they need to be replaced or can they be rebuilt with new seals? Keith
Hyd pumps wear internally then begin bypassing oil outlet back to inlet side especially at high demand loading. Can try a relief but doubt will affect it. If it is Not squealing like fluid bypassing when at high end then likely not ever coming off its seal. Back it off to original set point and do not bottom out a replacement.
Its not squeeling or making any unusual noises but the hydraulic noise does change when cylinders hitting their limits. The machine only has 2800 hours on it. Is it common for a pump to wear to the point of being down 800psi in that amount of time? It runs fine other than being a little low on power
Good day Kmacht According to our information your machine has a triple fixed displacement gear wheel pump, establishing power output is a combination of both pressure and flow - the benefit from fixed displacement is that it is reasonably easy to establish, a pressure that makes good at full revolutions and significantly reduce and low revolutions indicate leakage - this can be due to pump - relief valve - or the circuit used to test the pressure. In your case you use the blade which is not the best as between the pump and blade you have the central joint can this be subject to significant leakage distorting the results. I suggest you use another circuit using both high and low revolutions to measure the power. Gear wheel pumps can last 8-10 thousand hours considerably less if the fluid is bad. Hope you find the advice useful. Kind regards Uffex