hello all. I have a 235 caterpillar excavator that keeps blowing the hydraulic cap off due to pressure build up. I opened the pressure relief valve and checked spools. One of the spools were stuck, I tapped on it to free it and removed it to clean. It moved freely when i put it back in so i put all of it back together and still having same issues. At idle it will not blow but wants i raise the RPMs it will.
Give us a clue - Serial Number. There are 15 different models of 235.