HYDRAULIC PROBLEM

tripod61 · Dec 18, 2011

i have a 870 john deere with a loader & backhoe attachment. had to replace a cylinder on backhoe attachment & now the hydraulic system is full of air. how can i bleed this air out of the system.

KYErik · Dec 18, 2011

Assuming that the reservoir is full, just cycle all of the cylinders a few times. The air will rise and will bubble out of the fluid in the reservoir- so it will eventually work its way out the reservoir vent. But- if you have a leaking suction hose, more air will be introduced into the system.

Jerry/MT · Dec 18, 2011

KYErik said:
Assuming that the reservoir is full, just cycle all of the cylinders a few times. The air will rise and will bubble out of the fluid in the reservoir- so it will eventually work its way out the reservoir vent. But- if you have a leaking suction hose, more air will be introduced into the system.

Great answer. You saved me the effort of writing it!

J_J · Dec 18, 2011

Just cycle all the cyl in your tractor hyd system several times.

Actually, just because you changed a BH cyl, there is no reason to think air was injected into the system. The fluid from the BH should have gone to either 3pt, or tank.

If you think your pump is sucking air, look in the hyd tank with a flash light and see if there are lots of small air bubbles. Also allow some time for the air, if any, to settles out, and check again.

If you continue to have air in your system, recheck all the suction fittings, and pump flange.

tripod61 · Dec 26, 2011

there is so much air in the system, i cant work the hydraulics to get the air out. nothing will move. so much air is in the system, the fluid looks like foam rather than hydraulic fluid. should i leave the cap off the resivoir as i'm trying to bleed the system or should i put more fluid in, then put cap back on & try to work all the hydraulics. also about how much fluid should the entire system hold. just the tractor itself holds 5.5 gallons. this does not include loader on front & backhoe. any help is appreciated.

thanks, ricky

KYErik · Dec 26, 2011

You must have a sizable leak between the pump and the reservoir. You should try to track it down. If you can rig up a way to pressurize the reservoir with 2-3 psi (make up a fitting that adapts an air hose fitting to the breather opening) then you could look for the spot where the air and fluid escapes.

holt50 · Dec 26, 2011

hyd. problems. If the hyd. fluid is foamy and has that kind of air ,you should have brake and steering problems . I would park in level ground ,check hyd. fluid , add if necessary then bleed steering and put clear hose over bleed screws on brakes run the hose into the rear of tractor or hyd resovoir , pump brakes with pedals locked until air free fluid flows ,push down fast and release slow . should correct your problem. Holt50

J_J · Dec 27, 2011

With that much foamy fluid, almost sounds like the tank is almost empty and you are sucking mostly air along with some fluid.

Check all the fittings and hose from the reservoir to the pump inlet. Re-tighten everything good, or replace obvious worn or dry-rotted hose.

If the pump is sucking air, you can normally hear it.

Check the pump shaft seals and and flange and spray with oil if possible.

Use something to squirt oil over the suction line including the fittings. If you hear the pump sound change, you may have isolated the air leak.

You need to do the oil spray test after the bubbles have evaporated and you see clear oil. Maybe 24 hrs or more.

tripod61 · Dec 31, 2011

thanks for all the advice. i finally found a hose that was dry rotted & cracked and this was causing the system to suck more air in. replaced the hose & now everything is back to normal.thanks for all the help.