Pressure build up is caused when the air filter located on top of the Hydraulic reservoir becomes clogged, and stops the oil reservoir from breathing (allow air in and out).
This is a special 10 micron air filter for Hydraulic systems; its purpose is to keep dirt and other contaminants out of the Hydraulic oil.
The air filter will become clogged through everyday working conditions and should be replaced a minimum of every six months. Should the working conditions be extremely dirty, then it should be changed more often (every 3 or 4 months).
A regular oil filter that looks the same will not work and will cause oil leaks and gasket failures; you must use a special filter for air.
A clogged air filter may be checked by removing it and blowing in and sucking out through the center hole of the filter. If the air isn’t easily moved through the filter so that you can feel or hear it then the air filter is becoming clogged and needs replaced.
Oil residue coming from the oil reservoir will help clog the air filter and must be watched. Should this happen, the air filter should be replaced.
Before adding oil to the reservoir all the hydraulic cylinders should be retracted (i.e. lift cylinders down and winch cylinders retracted) with no oil showing in the sight gauge.
The oil in the sight gauge should be clear, not milky or air bubbly, and only filled to the center of the sight gauge leaving 4 to 5” of expansion room at the top of the reservoir.
Over filling with hydraulic oil, leaving the P.T.O. engaged, letting gravity lower the lift cylinders, or letting a container unload by gravity can cause the oil to entrap air and expand which will help clog the air filter and when this happens the air filter must be replaced.
New Roll off hoist users, inexperienced drivers, and untrained service personnel must be informed and cautioned to check and replace the air filter before it clogs causing pressure build up in the oil reservoir which will blow seals and gaskets and cause other leaks.
GALFAB’s air filter is Part No PH 12. We recommend using original equipment.