I have a customer with a D7H ser. # 79Z01640 and the blade lifts extremely slow. I haven't been out to it yet but I will check the obvious things; linkage, pressures and flow, cylinder leakage ect. Is there anything else that could cause this? I believe it has a ripper on it, does this use the same pump? I haven't worked on a lot of Cats so not real familiar with the system. Thank you.
Hey there, the ripper and blade share a common pump. Things to check: oil level and viscosity, pump noise (cavitation), cylinder drift, main relief should be set to around 3300psi, pressure limiting valve should be around 2500psi. If everything checks out then you may want to inspect the spools in the control valve for wear. There are also makeup valves inside the lift circuit section of the control valve that could plug up and cause slow lift cycle times. If you need a procedure for any of the above tests lemme know and I can PM you. Good luck!
Had same problem with old M F dozer ,ended up being piece of o ring stuck in pressure relief.
4T1860 valve should be the culprit raise the blade and hit the tilt at the same time and see if it speeds up
Hey guys, thanks for the info, I found a piece of metal in the main relief, popped it out and the blade lifts fine. No idea where the metal came from, pulled an oil sample and we'll see what it tells us. Thanks again.
Hey guys, I’m working on a d7 dozer. I had to pull out the steering, ripper, tilt and blade lift valves out due to a broken bolt going down all the manifolds causing a leak. Hoses are all back in the right position, hydro level where it should be and I’m using the right weight. I have dozer tilt but dozer won’t lift and I don’t have steering. Tried to bleed air out of the system for awhile today and still nothing. Any ideas? Thank you.
serial number please
hi I will assume (and you know what that can lead to) you are talking about a high track machine in most cases there are small shims between the valve sections. if they are missing or put back in the wrong spot when you torque up the through bolts it can distort the valve bodies and cause valves and spools to jam See if you can loosen the through bolts and try again that is assuming everything has been put back together correctly