Hydraulics rebuild

[Billy in TX]

The 3 pt hydraulic pump is worn out on my 52 8N.It bleeds down quickly with a 4" bush hog attached, and now won"t even lift it reliably. It has the swirling talked about here and I replaced the safety valve, no help. I want to pull the pump and rebuild it. I"m a good wrench and want to know if this is something I can tackle myself or am I better off taking it to the tractor shop down the road? I see 2 rebuild kits listed here, a Hydraulic Pump Overhaul Kit ($220.00) and a Hydraulic Pump Rebuild Kit - Comprehensive ($360.00). Which do I need? Anything special I need to know before proceeding? Thanks in advance.

 

[Bruce (VA)]

Chances are very good that you could rebuild the pump & it will still bleed down. Bleed down isn't a pump problem; it's a lift cylinder problem.

But, before we start....lets make sure we both speak the same language. If by "bleed down" you mean the lift arms drop w/ a load on it or as soon as you push the clutch in, and you replaced the safety valve, chances are very good it's the lift cylinder or piston that is the problem. Take the inspection plate w/ the dipstick off. Lift a heavy implement & look inside w/ the tractor running & the PTO engaged to see if you notice oil running from the top cover. If oil is running steadily from the top cover the lift cylinder needs to be rebuilt.

Before you start, it would be a wise move to get a jig from Zane Sherman to adjust the internal linkage. And, make a couple of “guide studs” by cutting the heads off of two 7/16-14 x 3 5/8” bolts. Also, if your lift cylinder rebuild kit has the leather washer, get CNH part number 87051231 which is the neoprene washer for the lift piston instead of the leather one.



The lift cover weighs nearly 100 lbs with the upper lift arms attached, & is very hard to maneuver. An engine hoist is an excellent idea. Remove the seat and spring, disconnect the upper lift arms at the knuckles. Remove the 14 bolts that hold the cover to the housing. (note that there are three different lengths) DO NOT remove the four nuts under the seat! Remove the right side inspection cover so you can remove the control rod tip from the pump intake valve. Lift the back of the cover straight up and slide a piece of wood under the cover to keep the tip of the control rod out of the rocker shaft. Once you are sure the control rod is out of the rocker shaft, you can then remove the cover. Turn the cover upside down, remove the four bolts that hold the cylinder to the cover, & use a little compressed air on the cyclinder to remove the piston. Check the cylinder for excessive scratches, hone if necessary. Install a new piston with "0" ring and backing washer in the cylinder. At this point, check the cam follower pin & the control rod. If the cam follower pin is worn replace it. Then, if you have a jig, adjust the linkage to specs. The ‘shade tree’ adjustment was to bend the control arm to compensate for normal wear in the linkage, springs & cam follower pin. If the control rod is bent, remove it & straighten it. (very carefully; they break easily!) Replace the gaskets under the cylinder and bolt it back on the cover. Put the gasket on the tractor (no sealer) and put the gude studs in place. Unless you do this every day or have eyeballs in your finger tips, get some help to guide the tip of the control arm back into the rocker shaft. (this is the point you will wish you had a engine hoist to hold the top cover while the control rod dances around the intake valve arm on the pump!) Align the cover holes up with the housing holes. Remove the guide studs. Tighten cover bolts, connect lift arms install the seat. Re-install the inspection cover with new gasket.
50 Tips

 

[Den N Ms]

Billy,Take your right side cover off,Disconnect the PTO shaft and start your tractor up with the bush hog attached to your 3 point and raise it up.Stut the tractor off with the bush hog still raised up and look up at the lift piston with a flashlight for leaks.The cylinder will have oil drippin down from it if its leaking.Or it could be the control valve or the lift cover gasket.

 

[wwalkersd]

(quoted from post at 13:30:51 02/22/09) Before you start, it would be a wise move to get a jig from Zane Sherman to adjust the internal linkage.

Slight hijack here, but perhaps relevant to others reading this thread. Zane's jig is listed as being for the 8N. Is such a jig not required/desired for a 9N or 2N, or is it just that nobody has built one? Also, can I expect a 2N top cover to weigh about the same?

 

[Dell (WA)]

Walker.......ONLY the 8N requires the "Zane Jig". the 9N/2N is "draft" sensing only and does NOT have the internal "position" control linkage that the Zane Jig helps adjust. .......Dell

 

[Steve (NC)]

I agree with Bruce. It is probably the O-ring around the piston. I just finished rebuilding the hydraulics on my Jubilee. Same problem. Discovered the O-ring around the piston was all broken up. I found the DVD on hydraulics rebuild to be helpful.
Also a little note, it took awhile for my pump to re-prime. I ended up letting it run for a while with the bleeder plug off with a pan underneath until the oil started to geiser out.
-Steve in NC