640 hydraulic pump

Russ207 · Apr 12, 2015

My old, tired 640 is still an amazing machine. I was doing some bush hogging yesterday when I noticed my right boot was getting covered with a fluid. I climbed down and looked at the hydraulic pump (ball bearing piston type). A fine stream of hydraulic fluid was coming out at the first seam behind the cover at about the 1 o'clock position. I tried tightening the bolts securing the cover - got about 1/8 to 1/4 turn on each but the stream was still flowing. I am hoping a gasket set will fix the problem. My question is, can I replace the gaskets behind the cover and plate without totally disassembling the pump as called for in the overhaul manual? I am hoping I can remove the pump, put in a vice with the cover facing up and remove the cover without losing the pump components or otherwise messing things up. I know I should take the opportunity to do things right but I am trying to help our small church clear our new 18 acre property on a rather tight time line and very small budget. My time, talent and tractor are free which leaves the money for other expenses.
Thanks

WayneIA · Apr 12, 2015

Put the pump in a vice, front or head up. Remove the 6 bolts. Might have to tap with a hammer as the gasket will probably have a firm grip. It will be spring loaded so hold on to the top when it comes lose. Watch for springs and balls. That shouldn't be a problem if you take the top off slowly. Get back to us if you have more questions. The gasket is usually a bear to scrape loose.

Russ207 · Apr 12, 2015

(quoted from post at 18:23:54 04/12/15) Put the pump in a vice, front or head up. Remove the 6 bolts. Might have to tap with a hammer as the gasket will probably have a firm grip. It will be spring loaded so hold on to the top when it comes lose. Watch for springs and balls. That shouldn't be a problem if you take the top off slowly. Get back to us if you have more questions. The gasket is usually a bear to scrape loose.

Thank you WayneIA. I ordered the gasket kit yesterday - when it arrives, I shall proceed as you suggest and I will post the results.

Kurt-NEPA · Apr 13, 2015

Replacing that gasket is straightforward. Just unbolt, clean and reassemble. The hard part is getting all the check balls and springs back where they belong. Your manual tells you how to do that.

If you are ordering parts, I would suggest you get the rebuild kit. It has all the gaskets as well as new springs and balls. I'm willing to bet your check valve springs are well worn.

Russ207 · Apr 13, 2015

Thank you Kurt. I was sort of concerned about the small stuff. I am bad about not finding every little thing that falls on the floor. Good advice on ordering the rebuild kit - shuda done that. The lift was performing well before the leak so I had already gambled and ordered just the gaskets. I will let you know if the gamble paid off.

640 hydraulic pump

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