air in hydraulic system

pasomike · Feb 8, 2012

My JD 4200 is building up air pressure in the hydraulic system. When I remove the trans fill cap it sounds like opening a can of beer. The oil is foamy white, but settles to normal after 1hr. I had overfilled the trans/hydraulic but only ran it for a short time until I noticed the steering and FEL acting up. The pump did not get hot. When it runs, some oil is being forced out past hose clamps on the suction side. Anyone ?

J_J · Feb 8, 2012

Tighten the hose clamps, I believe you have a suction leak.

Johnp33 · Feb 8, 2012

The suction leak is a definite thing to fix, both ends of that hose, if that does not do the trick, it could be the pump itself sucking air past the input drive shaft.
If it is doing that most times it will draw in motor oil and the level will rise and the oil will become discolored, black.
Just a thought!

pasomike · Feb 8, 2012

O.K. Tightened the clamps. The whole snafu started when I was fiddling with the starter and had to remove the 3 port suction manifold ? did the suction filter cleaning and filter changing drill, so I have to wait until tomorrow to purchase more friggin oil. i suppose if there were small amounts of oil getting past the hose clamps and I thought they were tight, then the next place to check would be that rubber manifold on the pump. Can't believe how much air pressure builds up in the system, you could launch a potato from that dude ! I'll let ya know how it works out tomorrow. By the way, is this system self bleeding ? Thanks so much.

J_J · Feb 9, 2012

Yes, the air will dissipate over time. If there is air in the cylinders , they will purge as you operate the hyd system.

Egon · Feb 9, 2012

Leave the oil fill cap of and run the tractor.

Sounds like the pressured system is forcing oil out where you see leaks.:thumbsup:

pasomike · Feb 9, 2012

Thanks Egon. I found the problem. The rubber manifold at the hydraulic pump had a tear in it. JD will have the part tomorrow. I'll let ya know how it goes. Thanks !!