|
jdemaris
01-02-2004 19:19:13
|
|
Re: 4520 Front Engine Seal or Hydraulic Pump Leak? in reply to 4520 Owner, 01-02-2004 07:58:25
|
|
| |
Leaks from the hydraulic pump are common ( at least when you work as a Deere mechanic). Sometimes it's just a piston cap (there are 8 of them). But, if you see oil leaking from the shaft, you ought to pull the pump off to fix it properly. What usually happens with the closed center piston pumps is, the shaft gets loose, then blows out the internal high pressure seal, and then blows out the dust seal - which is the only one you can see from the outside and is not capable of holding any pressure. The shaft rides on two adjustable Timken style bearings. It is adjusted with shims that go in the back cover of the pump. Proper end play should be around .002 - .005". To replace the seals, you must #1 remove the pump, #2 remove the cover from the pump (4 bolts as I recall), #3 take all the piston caps off and pull out the springs and pistons (8 of them), #4 then pull the shaft out of the pump, #5 replace the high pressure seal - it's a square sided 0-ring A.K.A. Quad-ring with a teflon backup washer, #6 replace the outside dustseal - looks like a plain old conventional seal because it is - usually held in with a snap ring, #7 put shaft back in along with cover and shim properly if needed, #8 put pistons, springs, and caps back in - pistons caps get o-rings with protective teflon sheafs over them. That's about it. If you do all this, and you've bought the proper seal kit from Deere, you'd be nuts not to replace the stroke control valve while you're at it. It's the main wear item in the pump. Also one note - try not to mix up the pistons if you have them out. Kinda' nice to put them back in the holes they came out of since their wear patterns will match the bores.
|
|
|
