435 ZHS swing problem

[CVF575]

I have a 2008 BC 435 ZHS that started giving me problems yesterday. All the hydraulics work good except when rotating the machine. Once i rotate it a few times back and forth it gets very slow and almost stops, even with the joystick pushed to swing left or right. If I shut the machine off, and restart it it will swing good right away, but slow down right away again. There are no visible oil leaks and no broken belts. What is my problem? TIA for the help!

 

[SSdoxie]

Is there any noise from the motor when it starts slowing down? Noise like metal squeak or screech? This could be motor brake not releasing due to debris lodged in orifice of sequence valve. When you move the joystick pilot pressure goes in 2 paths; 1 to move the control valve spool to send oil to motor for rotation. 2- pilot oil goes through a small aluminum block (sequence valve) to apply pressure to motor brake and release the brake. When you release joystick to neutral the pilot oil from the brake goes through an orifice in this block then back to tank drain.
Debris from the brake can plug this valve so the brakes either do not release or stay release all the time.

If there is no metal squeak noise form the motor, the motor may need repair or replacing. A pressure test of the motor would verify this.

 

[DDoyle]

Hey SSdoxie, you helped me with my 853 a few years back. The ole girl developed a loud knocking noise while plowing snow. Sure enough I lost engine oil. Given age and Hours what is your best prognosis?