S/n is agg00655 Problem is when lifting blade it drops 3 inches or so and then goes up Ive rebuilt control valve and found O-rings missing on resolvers on all banks primary and secondary I even replaced the 6 small ball bearings and 1 bigger ball bearing and piston and shaft on end of lift control shaft they all had flat spots on bearings Reinstalled valve body and same thing droops or drops 3 inches on lift the goes up I even put all new primary resolvers in because one on lift had more play at the end then the other 2 in tilt and angle Same thing drops 3 inches and the lifts Today I pull the make up valve which has the return oil restrictor in it and I see no wear ......Now I have torn valve body down 3 times cant figure out whats doing this Did a leak down test of lift cylinders in down position holding front weight of machine up a 1 foot or 2 its very lil leak down blade up till I hit stall 3000 psi I get very lil leak down All other tilt and angle work fine no problems its lift only Could it be flow conversator valve that on pump ? Or what else is there left I may be over thinking this looking at hydraulic schematics
Is the load check valve and spring OK? If it is, with the blade up and engine off, operate the spool in the lift direction. If the blade then drifts down, you're losing pressure somewhere in the resolver circuit or compensator. Eliminate the compensator by disconnecting the signal line at the pump and plugging it.
Thanks Cmark ....Its not compensator ... ill recheck load check valve as soon as I can .. had a cat d6h with a few leaks in torque convertor lines
Cmark ..I blocked line to compensator and it drifts down slightly ... being engine is off I could hear something from valve body when I moved lever to the lift position I got a coworker to move lever while I listened with a Stethoscope probe I swear the noise is in check valve I removed it and it pushes in fine but hangs kinda ...cleaned it and still hangs almost in on the diagram you posted it between 15 and 18 and is part of resolver circuit ... Called caterpillar had a 3 way chat with shop manager and hydraulic shop manager and was tolded by hydraulic manager he had that problem once in 20 some odd years and couldn't remember what problem was ...damn I'm number 2 to have this problem in 20 years lol I feel better