After a few months of working out issues with our 1989 "semi abandoned" Sumitomo-built beast we finally determined that our major issues were due to a badly worn pilot pump. We initially made an assumption that the pump was okay when in fact it was the original pilot pump and had some bad wear from the years of prior use. We found a number of other problems as we've been troubleshooting, all of them relatively simple and easily resolved. So after replacing the pump we now have good to excellent pilot and main pump pressures with all functions (swing, boom, arm, bucket) working correctly EXCEPT... Travel. Since this machine had sat for about 9 years it had been operating in rewired by-pass mode prior to our getting it, so we're dealing with basic functionality. We need to figure out why we don't have travel. Each solenoid valve has its own rocker switch so we can activate each separately. I'm not clear on how the travel motor brake is activated so any help is most welcome. Note that our travel motors are the four-hose configuration as numbered in the image. I'm guessing the #4 hose is brake? So what conditions need to be met to release the brake and allow travel? Many thanks, -Tom
The travel brakes are spring applied and pressure released when ever you travel. You have two supply hoses, a two speed travel hose and a case drain hose. Travel problems could be at the main valve, center swivel, the motors themselves or a broken final drive. There were a lot of problems with travel on those machines. They would develop a leak in the valving in the motor and go into high speed and stay there. We were never able to fix those problems and always ended up replacing them with new. I would probably just pull the center swivel out and tear it apart to check the seals. More than likely they are blown out.
The center swing joint swivel was resealed shortly before it was parked by the original operator in 2011, and there are no leaks anywhere. I don't know what was going on before being laid up but the machine DID travel over to its resting spot. The travel issue seems to have occured after being parked, and possibly after the O ring replacement by a good hydraulic shop. Your explanation of the spring brakes is a major clue, so is the #6 (smaller hose numbered as #4 on my photo) the case drain hose? What were not getting is any significant lugging of the engine when we try the pedals. I'm beginning to think that the problem might lie in the two-speed valve assembly or solenoid as you suggested. I just need to get deeper into tracking the lines back and testing the hydraulics. As always, thanks John!
The machine would still move in high speed travel using both the pedals. Just a word to the wise, there are no hydraulic shops that you can trust and running when parked is the same as alive before it was dead.
Understood John. We're going up in two days to test dead head pressures at the valve assembly (or rotating joint), and at the pump per advice I received from our local LBX Service manager. We have three pedals for travel (L, R, and both) and didn't try activating L & R at the same time. The two-speed function looks like it's just an internal piston or something similar in the drive motor that might engage a planetary gear for low or high operation. True? The previous operator should be up when we're there and I may get more background about what was done and when. But at this point in the game we're so close to identifying and correcting the problem I almost don't care what he may offer. BTW, if we have to pull the rotating joint does it come up out of the well or drop between the tracks? Looking at it seems formidable given how deep it sits in a confined space. But then so did the prospect of pulling the main pump which only took a couple of hours once we were set up! Thanks, -Tom
The two speed travel works by shifting the swash plate on the motor. Maximum swash plate angle means the motor is in slow mode while minimum swash plate angel means the motor is in high speed mode. There are no gears to shift. My people were set up for the swivel job and could complete it in the field in between four and six hours depending on the problems of age and debris that had to be removed. I seem to recall it coming out the bottom but all those things run together in my head anymore.
You've been a great source of knowledge and tips, John. Many thanks! -Tom