Dad's B

[Alan Steadman]

My Dad recently bought a B with a 5 ft woods? deck. The hydraulic pump sits under the seat and runs off the PTO. The pump will lift the mower a little (about 2") and just sit there and twitch. He went to the dealer and bought new seats, etc. Same problem. Bought a "good used" pump, same problem. If you pull the hose from the cyl, it sort of pulses, not a steady flow. With a piece of rubber pressed against the end, it will spray but not much (Very short test, then refill on tranny) I know the levels are good, non-detergent sae 20 as per book, 2 pumps doing the same thing makes me think it"s the lobes, but they do not look very worn or misshapen. There IS a lot of air in the oil, (tiny bubbles) and we have bled the cyl & hose twice to remove air pockets. After 3-4 tries, I can actually move the arm by hand some, like there's air in it. Help, very confused and on unfamiliar ground with this color tractor. Thanks - Alan
e-mail: mh81@windstream.net
 

[carbonfibers]

I think you have the answer. Based on what you are describing , it is vapor locked. There is air in the pump or some type of pump suction blockage.

Wayne
 

[Mark - IN.]

Well, my B doesn't have hydraulics and I've not seen one up close enough to see the setup, although know that they're out there with loaders and 3-pt hitches that have been added after the fact. I didn't know that Allis ever offered factory hydraulics for a B, but maybe they did. But I'll take a stab at it, that it certainly does sound like air is getting into your lines. You're using the trans as your reservoir? That's got to be additional oil to that already up to the filler plug. Hmm? Then I'd think that both your pump input and return have to have replaced drain plugs at the bottom of the trans where there's a constant source of fluid. What comes to mind is the gears constantly meshing and churning air into the trans oil or a low oil level when the pump's sucking and filling, and you may be sucking that air into your pump pickup. If this is a factory setup, then perhaps an open or stuck bypass in the control valve comes to mind. What are you using for a filter for the hydraulics so dirt and stuff isn't working its way into you lines?

I've thought about adding a 3-pt to my B for smaller stuff, but figured that I'd add a seperate reservoir for a pump driven by the rear PTO shaft which never gets used. They typically have screens in them that strain and baffle fluid for air pockets.

Mark
 

[old]

The B and C both can come out with Hyds., Both use the transmission area as the fluid supply for the pumps. I have a C that I built a 3 point for and also a front lift and both work well. I did use cylinders off of a WD instead of the smaller ones that came on the B/C
Hobby farm

 

[Rex in Australia]

Sounds like it could be sucking air, pick up screen blocked perhaps?
Rex
 

[Mark - IN.]

Never knew that old. Never saw one. I've seen them with aftermarket 3-pts, saw a photo here of one with a loader, never saw the pump setup.

Mark
 

[Dick L]

If you let the discharge hose pump back into the transmission for a bit the air in the pump would be out of the system. It will also work its way out over a short time just trying to get it to lift.
My guess you have something a miss in the ball check valves or directional control valve. You can get the control shaft out of the proper position.
Take a look at the drawing.
When the piston comes back out if the checks are holding it will draw oil up in front of the piston. If the bottom check is holding the oil would be pushed up and out the hose (if) the oil is not being directed back to the transmission.


 

[old]

Pump runs off a cam in the PTO system. Its a high pressure low flow system. Tranny rear end and hyds are all the same fluid supply. On my C I extend all the cylinders then fill the tranny so as to have an over full system but doing so helps because of using the bigger cylinders.
Hobby farm

 

[D13]

Check that the cam lobes on the PTO shaft are not totally worn. Once they geth thru the face they go flat quick, particularly on a mower tractor where the PTO or belt is always in use. Also be sure you have the correct pump and cam (4 or 2 lobes).
 

[Alan Steadman]

Tried running back into the tranny, it still sort of pulses and still lots of bubbles, still not enough pressure to lift. the pickup on these is just a street elbow with a short stem pointing down. This is the same on both pumps so it must be factory or both these guys shop at the same place. Does anybody have a spec on the lobes on the PTO shaft? It acts like only one side is pumping. Next step is to drain & pull the pump again and measure the lobes for distance to the case, see if they"re the same.

Thanks for the info everybody!! I"ll just keep playing with it, sure would help if there was a view plate on top... then I could see the lobes in action. - Alan
 

[cmoody]

was raised on a c tractors, the "b" had a factory lift system, and they would get air in the system that would have the symtions that you described, without any equipment on the lift raise the lift all trhe way up, loosen the flange nut on the ram just enough to allow the oil to come out; continue until there's no air bubles,the verry small ones, only clear oil, then tighen the nuts back to seal the ram back ,no leak, this should get the air out of the whole system especialy thr ram,, you are compressing air in that, no lift, get containers, mab be messy, keep the level up in thr rear oil up too!