Foaming Hydraulic Fluid

[bucky7680]

I have a 12V electric over hydraulic dump trailer. The motor, pump, and reservoir are all one unit. The cylinder is power up and power down. When I power down the cylinder the fluid starts to foam in the reservoir and begins to over flow before the bed is all the way down. I have to wait at least 5 min before I can try to lower the bed some more. I usually have to do this 2 or 3 times. The dealer, who has since gone out of business, told me that because it was new it had air in the system that would work its way out over time. I have lifted and lowered the bed about 10 times and things did not change. Since I bought it the speed at which the bed raises is the same if it is empty or when I had a load. The most weight I?ve had is 2500 lbs in the bed. The trailer is rated to lift 6000 lbs in the bed. When the bed is up high enough for the load to dump the reservoir is empty. There is some more stroke in the cylinder if I had more fluid in the reservoir but the foam over flow would start sooner. I drained as much fluid out as I could and replaced it with new hydraulic fluid from Wally World. It foamed just as much. I was told to use power steering fluid. I again drained as much fluid as I could and replaced it with power steering fluid. It foamed just as much. I was told by a guy at the dump with a dump trailer to use AT fluid.

Will AT fluid work?
Is there an anti-foaming additive I need to use?
Was the dealer correct and I still have air in the system that needs to work its way out?
Is there a problem with the pump?

I love this trailer and it is not a low end brand.

 

[HappierWet]

Re: Foaming Hydraulic Fluid

If it foams there is still air in the system. Use hydraulic fluid. ATF or power steering fluid works but is not really designed for this purpose. The farm store or maybe your local auto parts will sell hydraulic fluid for farm implements.
Question.....When your bed lifts does the cylinder tilt (lift at one end ) or does the cylinder stay flat and actuate a slide or scissors device?

If the cylinder tilts you almost certainly have air trapped

 

[Bamby]

Re: Foaming Hydraulic Fluid

When the bed is up high enough for the load to dump the reservoir is empty. There is some more stroke in the cylinder if I had more fluid in the reservoir but the foam over flow would start sooner.

Here is the probable problem. Inadvertently by running out of reservoir oil before top of stroke lift you are pumping oil/air into the hydraulic system. Try putting a catch basin under reservoir and raise the bed some as bed lifts observe oil level in tank adding a bit as needed to keep pickup under oil as bed is lifted. When cylinder is at top of stroke the pickup should oil level that it at least covers it excluding any air entering system.

Then lower bed and raise bed as necessary to work the air out of system. When you work the air completely out of the system the foaming issue will then go away. The catch basin is just a precaution to catch any surplus oil should you happen to overfill the system. When you get it right, carefully observe the oil level so you'll know where to fill it to for future reference.

 

[royal0014]

Re: Foaming Hydraulic Fluid

Use specified hydraulic fluid, NOT P/S or AT fluid. Every time you emptied the res. you compound the problem by allowing air in. If the cylinder won't go full stroke w/o empting the tank, either the tank is not filled to the proper level, or the tank is not big enough. Also, check and double check connections between tank and pump, it could be sucking air!

 

[bucky7680]

Re: Foaming Hydraulic Fluid

Thanks guys. I'll gat some more hydraulic fluid today and see if I can work the air out of the system. I'll keep you posted with the results.

 

[dolluper]

Re: Foaming Hydraulic Fluid

low oil level will cause foaming as explained so well above fosure....but top piston loose packing can also draw air....it's forced in when you withdraw the piston....I've seen the packing so bad you get a shower from it and no foaming because the tank level is fine

 

[bucky7680]

Re: Foaming Hydraulic Fluid

THE RESULTS ARE IN:

Finally after extending and retracting the cylinder approx 20 times I was able to work all the air out of the system. The biggest problem was waiting for the air bubbles to dissipate before I could work more hydraulic fluid through the system. It took me 3 weeks to get all the air out. I'm glad I got the on board charger option. Thanks Bambi, your advice was spot on. Now I can really get in and out of the dump in record time.