I have a very funny problem with one forklift. it works well say for 3 hours then it looses lifting power or force. We are a brewery so when it starts that then we only use it for moving pallets with empty bottles that are lighter. I have already changed the pump. I checked it today and the problem is only on lifting, tilting is ok. The pressure is 185 bar and i think it should be sufficient. What could be happening? it only does that when the oil is hot