JD 4200 Hydraulics Jerking

BobVogler · Jun 14, 2010

I just replaced a leaky hydraulic input manifold (3 port rubber device) and refilled with hydraulic fluid. Now both the steering and the 3 pt hitch jerk like there is air in the system. I've tried to bleed the air out of both systems by turning lock to lock on the steering, and cycling the 3 pt hitch to the top and bottom of travel -- still it jerks and both systems respond very slow.

Did I damage the pump while running low on hydraulic fluid? - or can a stopped up input screen or filter cause this?

I just bought the 4200 used with 275 hrs, and have only put an additional 25 hrs on it -- the screen was recently cleaned just before I bought it.

kennyd · Jun 14, 2010

Welcome to TBN Bob

The system is self-bleeding, so what you did to should have gotten rig of any air. You can damage a pump by running low on fluid, or by having a suction side leak causing the fluid to foam and the pump to cavitate. I dirty filter/screen can also cause this because the pump will starve for oil.

Can you be more descriptive about he part you replaced? Is it the big molded elbow that connects to the pump?

BobVogler · Jun 14, 2010

Yes, the rubber elbow on top of the hydraulic pump is what I replaced.

I guess the next step is to look at the input screen and replace the filter. I think I probably have too much fluid in there at the moment -- does that cause harm as well? I'm new to tractors and everything I need to watch out for. But I'm learning fast -- I may have just blown $1000 by killing the pump.

I read one post that said to point the tractor down hill in order to make sure the fluid goes into the pump. How will I know if the pump is bad -- by process of elimination? I've not seen any leaks anywhere since I replace the rubber piece.

Anyway, thanks for you comment. There appears to be a lot of helpful people here on this forum.