air in hyd lines/pump????

[jeff 262]

I have a cub 3235 change gerotor in the hyd pump. Flushed the system. Still no power to trans or deck lift. The steering has some power. I think there might be air in the system. How do I get the air out of the system. Thanks for any help jeff 262.

 

[Tom Arnold]

I am a Case guy, not a Cub guy. However Case tractors use hydraulic drive and I am very familiar with them.

Normally, there is no "bleeding" of a hydraulic circuit. Once the pump is receiving oil via gravity from the reservoir, any air in the system will be pushed on through to the reservoir. It's just a matter of running the tractor at idle and making any cylinders go through full travel a couple of times and running any motors that might be on the tractor or on any implements.

If your tractor isn't pumping oil or if the oil is foaming (look in the reservoir with the tractor running) then you need to take a hard look at the line between the reservoir and the pump inlet. Are the metal fittings going into the pump properly sealed and tight? Is the suction line in first-class condition? Are the clamps that secure the suction line really tight?

If the suction line is old.....replace it with a proper suction line from a hydraulics house. Don't use any other type of hose. Old suction lines can develop pin holes that allow air to come in but won't necessarily allow oil to leak out. They can also de-laminate internally and when this happens the pump sucks the inner liner closed and starves the pump. Gear clamps are a bad choice. Use the band-style clamps. These are a smooth band of metal that are bent 90 degrees at each end and a bolt/nut pulls those ends together. Hydraulic hoses are thick and gear clamps often fail prior to sealing well.

Lastly.......are you positive that you are using the absolute CORRECT oil for your system? You use the term gerotor. Case tractors use gerotor style motors to propel the tractor and to power the rototillers. You cannot use hydraulic oil in a Case. You must use motor oil only. Perhaps your Cub is the same way. Gerotor motors have lots of clearance inside compared to vane or gear-type motors. Once hydraulic oil warms up, the performance of the gerotor motors falls off. We recommend using Shell's Rotella T oil in either 15W40, 20W50 or a straight 30 weight.

If your tractor ran OK prior to flushing out the old oil, then one would think that the pump is not the problem. If your reservoir is below the level of the pump inlet, then perhaps you need to use a bit of compressed air in the reservoir to help get the system primed.

Sorry but that's all I got for you. There are forums out there strictly for Cubs if the above doesn't help. Send me an e-mail.

 

[El Toro]

Are you sure you have enough fluid in the system? Working the system as Tom suggested should bleed the system. Take a look a the suction hose to make sure it isn't being sucked closed. If it is replace the hose from Aeroquip or Alemite. Hal

 

[Rusty wheel]

Howdy. I"ve had some experience with Hydraulics from very basic systems to very complex. Some systems can trap air,especially when they are completely drained. If you can find a gauge port on the pump, install a gauge. Make sure the bypass valve is closed. If you can find the pressure relief valve, open it. Make sure the fluid level is the correct type and the fluid level is correct. Start the tractor. Run it about half throttle. Start closing the relief valve slowly while watching the gauge. If the presssure comes up but nothing moves, crack an output line and see if any oil is comming out. If the pressure doesn"t come up, you may have to bleed the pump to allow the oil to flow into the pump. Also, feel the lines and pump for any heat buildup. One question, is the pump inlet flooded? that makes a big difference....RW