Bobcat S650 won't lift load at low rpms sporadically

[Apakesha]

I am working on a Bobcat S650 and the machine will not lift a load when the machine is at idle. If I increase rpms it will lift. It originally did not do this. Any suggestions?

 

[brdgbldr]

Lifting a load at idle speed is not real common but since you said it did it before and now it doesn't let's try to find out what's different.

Is the load the same weight, including the bucket, forks etc.?
Did you do any work on the machine just before this problem started?
Is it idling at a lower rpm now then it did before the problem?

 

[Apakesha]

My friend brought me his skid steer loader giving me the opportunity to solve his problem.
When I got it, the lift would go up and down with no problem. So I asked him to bring a bucket to try to replicate the problem under actual conditions. I got it attached and had no problem raising and lowering it. So then I moved over to my pickup truck and lifted the back end of the truck up and down with no problem. then after about 15 minutes the lifting went from fast up and down. to slow up and fast down. All this was at idle. If I sped up the throttle it would go up, but still slow.
I called the dealer and spoke to the service tech and he said that he thought that the pump was going bad. I got the impression that he did not have any interest in helping me.
There is no other problem with the machine. The machine goes forward and backward perfectly. The tilt works both ways perfectly. The only problem is when the lift is going up. I can tilt the bucket down and move the lift down to the ground and beyond and it work perfectly.
One thing I did notice is. if I put my heel to the tilt pedal and raise the lift with the lift pedal at the same time it goes up fast as it should.
The machine would not do these things if the pump was going out. The hydraulics stay up and do not leak down. I'm thinking there is a restriction in the lifting section of the hydraulic system.

 

[brdgbldr]

Not sure I can help much here other then give some ideas.

To me it sounds like something going on with the valves. Something sticking somewhere. Maybe a bypass valve stuck open.

When you say tilt the bucket up and the lift up works better, are you holding the tilt up peddle all the way down? This would cause a bypass to open when the bucket is tilted up all the way, since it has nowhere to go. Not sure if this bypass could help charge the lift pressure.

Does the Machine have the option of bucket possition valve? Not sure what would happen if something went wrong with that valve. I mention this because of the tilt peddle "fix"

Long shot…Not sure of your machine, specifically since it had the option of several different controls, but make sure you didn't somehow turn on the auxiliary in the lock open possition. This is pretty hard to do with electronics, but easy with manual controls.

Hopefully someone else on here can give you a more specific answer.

 

[Apakesha]

When I get the lift pedal to raise the bucket I just barely crack the tilt pedal in the up position. That lets the lift go up fast.
Another thing that I discovered is this machine has an auxiliary button on the dash. When I push that button it activates the auxiliary system. If I raise the lift arm using the pedal and hit the auxiliary toggle on the right joystick at the same time the lift arm works fast.
I removed a couple of the lift check valves and cleaned and inspected them and the main relief valve as well. Tomorrow I am going to drain the hydraulic reservoir and remove all the other check valves and other valves and solenoids on the hydraulic control valve and clean them and inspect them. I need to drain the reservoir to prevent hydraulic oil flowing all over the place as it did today when removing and cleaning what I did today. I was able to work through the flow of hydraulic fluid flooding everything as I was able to thread jic plugs in the hydraulic control valve.
Draining the hydraulic reservoir will make it a cleaner job.
I was fortunate that my friend has maintained this machine pretty well and I pressure washed it berfore working on it. The machine cleaned up and looks like it is new despite it being 12 yrs old. That is one of the benefits of living in Alabama where there is no road salt to corrode anything. Coming from Illinois (rust belt) this machine would be half gone from corrosion.

 

[brdgbldr]

Sounds like you've got this covered. Please keep us posted With your progress.

I always have a large set of JIC plugs and caps handy whenever I work on any of the hydraulics. Even if you empty the tank, there is still fluid in the system that will leak out.

 

[Apakesha]

Success::::::: Finally got it fixed.

I did everything that I possibly could think of. Watched hour and hours of youtube videos. Spent days removing check valves, testing solenoids, removing solenoid posts etc. etc. etc. About drove me nuts....

Adjusted the left pedal. That was it. Finally done with thing.

 

[brdgbldr]

Success::::::: Finally got it fixed.

I did everything that I possibly could think of. Watched hour and hours of youtube videos. Spent days removing check valves, testing solenoids, removing solenoid posts etc. etc. etc. About drove me nuts....

Adjusted the left pedal. That was it. Finally done with thing.

Well done. Slipped or loose linkages are hard to diagnose. You were on the right trail with a valve problem. Just had to figure out what was causing it.

Thanks for sharing the fix. Someone will find this useful in the future.