Removing air from hydraulic system

[rutwad]

After completely draining the hydraulic fluid and changing filters on my Massey Ferguson 5465, i need to bleed the air. Does anyone know the procedure?

TIA

 

[DwayneB]

Usually just operating all the hydraulics will do it.

 

[rScotty]

Why? What's happening that makes the air bleeding necessary? I've wondered about that. In theory, there should be quite a bit of trapped air - especially if the hydraulic cylinders got moved when the sump was dry, and that air should act like a spring in a system where everything else is designed to be incompressible. But in reality, I've never been able to "feel" any air in a tractor hydraulic system after an oil and filter change.
.
Still, it's my practice to run the loader, 3pt, ps, & backhoe hydraulics through a couple of cycles after a complete filter & fluid change....not that I've ever noticed cycling the hydraulics as having any effect one way or the other. It makes me feel better if I do it, and that's worth something. Maybe it will work for you,

Point in fact, I've rebuilt boom cylinders on both of my backhoes through the years. As you may know, BH Boom cylinders have a lot of volume. There's no doubt that when I installed them on the machine they were full of nothing but air, and also no doubt that by the time I started the tractor and rotated the seat around to try them out they seemed to be working normally. No compressive air effects that I could tell.

Hmm....I have heard some people recommend to put the hydraulics in a position so that they can work the levers and use gravity to compress the cylinders while the sump is empty. The argument is that this "gets all the old fluid out". I don't know how true that is about the old fluid, but it would seem to be the one sure way to get a lot of air into the system. I'll have to try that someday when I' bored of the same old oil and filter change just to see if I can see the effects of air being compressed.

Let me know what you find.
rScotty

 

[rutwad]

Dwayne, I thought the same thing and it eventually may. I ran it with the bush hog about 1/2 hour and it didn't make any difference. I just got off it again this time pumping the brake pedals and clutch, cycling the 3 point hitch up and down, and also operating the rear hydraulics. Nothing changed.

I recently bled the brakes on my backhoe, but it is a separate system. I think the same hydraulics on the tractor are used for transmission, clutch, brakes, and steering. The steering seems normal, but no brakes.

I see what may be a bleed valve on top of the axle near the brake line connection, but i wouldn't think you would bleed the entire system through the brakes. I'm guessing the same axle is used in other models that may be different.

 

[DwayneB]

Dwayne, I thought the same thing and it eventually may. I ran it with the bush hog about 1/2 hour and it didn't make any difference. I just got off it again this time pumping the brake pedals and clutch, cycling the 3 point hitch up and down, and also operating the rear hydraulics. Nothing changed.

I recently bled the brakes on my backhoe, but it is a separate system. I think the same hydraulics on the tractor are used for transmission, clutch, brakes, and steering. The steering seems normal, but no brakes.

I see what may be a bleed valve on top of the axle near the brake line connection, but i wouldn't think you would bleed the entire system through the brakes. I'm guessing the same axle is used in other models that may be different.

Don't know much about a massy but my john deere has bleeder valves on the axles. I'd try that.

 

[Tx Jim]

Don't know much about a massy but my john deere has bleeder valves on the axles. I'd try that.

There's no real need to bleed the brakes on a JD 2240 unless the brake pedals feel spongy or have little to no resistance when pushing on pedals EVEN after changing hyd oil. Only way for air to get in brake reservoir when ""changing hyd oil is to pump brake reservoir DRY"".

 

[Pete O]

I've bled cylinders after they have been dismantled- thus full of air- by alternately inverting the cylinder whilst it is being extended & retracted under hydraulic power so that air is pushed out of the cylinder. This would only be necessary if the cylinder has been removed from the machine and air has been allowed to enter. This is not going to happen with a routine fluid change.

 

[David_Kb7uns]

The only real concern I have seen in any of the manuals is Kubota suggest allowing a HST machine to sit without moving for several minutes after changing the HST filter so that the charge filter and system for the HST is bled of all air.

David