just got finished getting my d5c back up and running. i am having an issue with the blade angle not holding position when pushing no mater what i do. new valve section from cat on the angle circuit - no change new seals on both cylinders - no change new lines/no leaks - blade operates as it should right to left etc. all be it slow but still operates as it should hydraulic tank full other functions work perfectly fine pressure checked at 2500psi per manual at valve block inspection port completely stumped as to why it would be "bypassing" the way it is and not holding the blade angle position the way it should. please help **i did see check balls in the end ports of the angle cylinders but i don't see how that would cause my issue** serial number 8zs00282
To eliminate the cylinders try temporarily removing the hoses at the cylinder connections and installing blanks on all the ports. If the cylinders are bypassing internally that should show it up. Do you mean #1A as shown in the diagram.?
Yes, I’m not sure if they have them or not but curious as to why they would have these
I'm not sure of their function either, which is why I posted up the illustration in the hope that someone else knows.
I spoke to a friend who knows hydraulics pretty well and states those are essentially used as a counterbalance safety feature. I’ll try the plugs this weekend
Hy guys, I´m not expert in hydraulics... but have done my share of repairs and fixes... There are actuators with drift lock valves , but i dont think is the case in a tilt cylinder, but if it is the case u´ll find the hoses conected to a slide valve in the actuator, that valve is spring loaded in both ports closed, the rise in pressure in one port alow the valve to slide and fluid enter one chamber, fluid out the other. This system does prevent cylinder drift almost to 0 , due to the inequal volume chambers rule, even if fluid goes across the piston, the cylinder does not drift as the fluid in one chamber can not go(does not fit in the other. (theory) But...Most Hydraulic systems do not have this valves, instead the Main Valve has a some gadgets that mimic this. Of course the spoll keps the ports closed, and in the upstream fluid is at system pressure to both ports, this avoid for drifting due to small leaks.(at least when system is at working press). BUT the MAX press relieve Valve, wich is part of the Main valve body, is rated much above the working press, and is responsible to avoid system damage when cylinders are rammed. Very often this valve give problems... if this valve is not holding well cylinders drift and also they do not hold when rammed. IF u´re sure your tilt cylinder was repaired correctly and the closed port test does not show drift, u´d better start looking at the MAX RELIEVE valve, of course as we understood u messed with the main valve. Probably thats where the gremlins are. Good luck
When you block the ports only block one at a time or all you’ll be testing is the rod seals.
thanks guys. i tested the main relief to 2500psi per the manual the raise/lower circuit of the block hold the blade up fine and lifts the nose of the dozer in the air the tilt function is the same - no drift ill try blocking the ports and isolate line vs cylinders vs valve the weekend and see whats up
so here is what happened, the previous owner had the lines mixed up. i got the schematic for cat sis and played around with the hoses for a few hours and got it to work. funny thing is, they way they had the lines it worked correctly but would not hold as stated. tested the cylinders by plugging off the ports, held firm pushing against a tree. all in all, back to working properly as designed, thanks for the advice all!