Hello All, Tonight while using the excavator noticed some oil up on the back of the boom. The swing motor popped the dip stick out of the level tube and started pushing fluid out of it. What did I do? Help !! Please? Not sure if it is relative or not, but the machine may have 10 hours on it since rebuilding the final drives. It seemed to move around fine and was digging without issue. SN 3AW02476 9,560 hours on the excavator. Nick
Case pressure blew the motor seal out, could be just a worn swing motor, could be high case pressure related to a plumbing issue, cooler issue, bypass valve issue.... Gotta fix the swing motor first, and inspect the gearbox, then check the plumbing and check case flows and/or install a pressure gauge to check case drain pressure. 10,000 hours, if the drives were tired, the swing probably was too...
Thank You. In looking at the parts book I can identify the seal and or bearing/s involved to potentially allow that to happen. Regarding checking drain pressure, can you advise as to what I should expect to see if there is not an issue drain wise? Unfortunately, I do not have a service manual to reference those details or the disassembly/reassembly procedure. If anyone has access to that info, would appreciate it if possible to share it. Thank You..
I don't know this particular machine, but generally speaking motor shaft seals are good for up to 30 or 35 psi case pressure continuous, maybe double that on a cold startup or whatever for a short time. You would like to see less of course, 15-20 psi or less when working at operating temperature. All the drains run together and through the hydraulic oil cooler typically, so any restriction or any component with excess internal leakage can raise the drain pressure for all concerned.
Don't sweat it. Like lantraxco said cold start and swing blew the seal. Had it happen before on the same 3aw machine. Its a easy fix, pull the swing motor and replace the seal.
Thank you for the replies. Pulled the swing motor, replaced bearings and seal. O rings, all seems to be good. Replaced the return filter as well at the same time. Should be good to go for awhile.
As noted, the removal and repair was straight forward. 5 hydraulic lines, a dozen(+/-) mounting bolts, one electrical connector. Lifted it out by hand, guessing 100 lbs ish. Once on the bench, removed the four allen head bolts, pulled the brake piston out, the friction discs and spacers, then the rotating assembly. It was noted during the visual inspection that the drive end seal of the motor had rolled over allowing hydraulic oil into the swing gear box and ultimately out of the level (dipstick tube). The seal did not look damaged but was not pliable when checked out of the housing. Bearing did not seem damaged, no other problems found. Replaced the main lower bearing and cone, replace the drive end seal and all of the O rings. The smaller caged needle bearing at the top of the motor was fine and not replaced. The swash plate and all pistons looked like new. Performed a visual on the gear box, all parts looked like new, drained and replaced the gear box oil. Reassembled the motor, filled with new oil while on the bench, reinstalled the motor onto the swing drive gear box. Test ran the machine and all seemingly was back to good. Attached pics as they are worth a thousand words for sure.