530-345-4685 | 1431 West 5th St. Chico, CA 95928 info@rdhs.com

Occasionally we are all frustrated with our apparent lack of knowledge or understanding of a particular operating system. In truth, every one of us who own and operate equipment can understand our hydraulic systems we use if only we had time to learn and dive into them. With this idea in mind we decided to help those who will take a few moments to read further. Most actuators are either rotary ( motors) or linear (cylinders) so the problems described below may be common to both.


The cylinder moves slowly or does not extend or stroke all the way.
The motor or cylinder has a jerky movement to it.
Here is how you might be able to pinpoint a problem, following some simple procedures:

First. Check the fluid level in the reservoir. Maintain a 10% air space above the fluid level for expansion of heated fluid.

Second. Check to see if the system has a valve between the reservoir and the pump. Is the valve open all the way? With the valve open, check to see if fluid flows freely from the reservoir to the pump inlet. If fluid does not flow freely then investigate and solve. Look for a clogged or dirty suction screen.

A customer brought two Cat. blade cylinders in to be resealed. We resealed the old cylinders and the customer went away thinking his problem was solved. The next day we got a phone call asking why the blade would not raise. The long and short of this story is that the suction screen was plugged with red silicone they had used to seal the reservoir inspection plate. The pump was unable to pump fluid because the inlet was clogged.

Third. Check to see that the actuator handle is able to move through its full stroke – many problems could have been resolved if mechanics or operators would check for obstructed movement of the valve spool. Many times we have found worn linkage or push-pull cables to be out of adjustment.