This can happen for different reasons. Here are the most common.

1. The system or jack is over filled. Especially a problem when a tank has been topped off while the cylinder (A.K.A. actuator) is left extended, which makes it full of oil, so that once the cylinder comes back down to the completely retracted position, the excess oil takes the path of least resistance which is most likely the filler vent cap on the oil reservoir. In extreme cases we've seen plastic and rubber filler caps blown right out of the tank filler port. Also, in this scenario tank gaskets can get blown out, plastic and thin metal tanks can bulge or crack from the pressure that can result with non-vented reservoirs.

2. The oil level is too low. Low enough that the intake port or pick-up tube in a reservoir is able to draw in air. This can cause aeration of the oil and as that bubbly or foamy oil rushes back to the tank, it can be more than the tank volume and can come out of the vent cap.  There are other ways the air can be introduced into your system that we will cover in another blog post.

 

 

Other symptoms of low oil and/or aerated fluid in a system.

  • The cylinder is not moving at all, very slow or intermittent.
  • The actuator cylinder and/or manual pump piston is spongy or jumpy.
  • The pump whether manual, air or electrically driven takes longer to start actuating the cylinder -All the pumping before the cylinder moves is the time it takes for the air in the system to be compressed enough to start moving the actuator.

Can this damage my system or cause a dangerous condition?

Air being introduced into a hydraulic system can cause Cavitation and in turn possibly cause severe damage to moving parts and potentially a dangerous situation to the user and anybody else around the hydraulic system or related machinery.  This would most likely be an issue with high flow type systems, not with manually operated tools and jacks and hydraulic press set-ups that don’t operate at high RPMs.  If you suspect that damage has occurred it’s best to stop using the equipment before more damage can happen, possible rendering the equipment beyond economical repair.

Manually operated devices like hand pump and cylinder set-ups, most jacks, hydraulic knock-out sets, crimpers and cutters, being over-filled or under-filled usually isn't as damaging to the tool like Cavitation as described above. None the less can cause problems resulting in a potentially dangerous situation – Never attempt to work on any kind of hydraulic equipment that is under load or has pressurized lines. If you aren’t sure – STOP - find out. It’s not worth an accident!

Basic Hyd System

What can I do to remedy the problem?

  • Important note: Before working on your system or tool, ALWAYS consult the owner’s manual or contact the manufacturer of the equipment you are working on - The following steps are only a basic, general guide, and not to be used as a substitute for the manufacturers guidelines for the specific equipment you are working on.
  • With your cylinder rod (A.K.A. piston) in the completely retracted position, check the oil level of your jack or system. Top off to recommended level and try actuating the system or tool again. Extending the actuator and retracting a few times may be needed to purge all air.  If this initially fixes the problem but it reoccurs, your system is likely drawing air from someplace other than the intake in the tank and needs repair.  Also, keep in mind that not all jacks and tools are self-bleeding.  Generally, a system, jack or tool will purge air if the cylinder is below the elevation of the oil reservoir.
There are many variations in designs of hydraulic jacks, tools and systems.  Some may have special bleeding procedures specific to them – Don’t hesitate to call us if you need help getting the correct service instruction or parts manuals for your equipment!    Work Safe!