8n hydraulic pump question

[Model 660]

How can you tell if the pump needs a rebuild? I'm working on one for a neighbor that the lift was weak and out of
adjustment . Piston had just the o ring and the cylinder is scratched. The pump seems to be tight with just very very
slight sideways movement of the pump pistons. Any thoughts appreciated

 

[JMOR]

The way to determine if a pump is good or not is to determine whether or not it will deliver the specified pressure and flow through measurements.

 

[Model 660]

Thanks for the reply. My first time into one of these. The oil I
drained out was real thick compared to what I'm putting back.
The owner told me he's never changed it and he's had it for
decades. The oil I'm going back with is the 90w tractor supply
ford oil. I plan to replace the relief valve also. I had no way of
checking the pressure.

 

[Tim PloughNman Daley]

You can do a relatively low budget pump cleaning R&R without having to drop the pump itself, but the best way is to pull it and go thru the entire system. Email me and I will direct you the other site where you can get a FREE download of my article as well as methods of a complete pump rebuild. The pump could have a crack in the base or walls. The reason is people leave the machines stored outside and rain, sleet, and snow get into the system and not only contaminate the oil, but will freeze and then when the operator tries to run the hydraulics, the pump is frozen and thus busts up something. The chambers get plugged up with crud too and only add to the sluggishness. I'd suggest that you get a new cylinder as well. The grooves in the wall were made from the old three-ring style piston while system was low on oil. Honing won't correct the problem in my opinion in most cases, and since you have the top cover off anyway, just spend the $$$ now and do it right the first time. Some kits are available that have the complete gasket set, a new cylinder, a new piston, and O-Rings, and all can purchased at any of the Ford Tractor suppliers around. If there is chance that the system has water contamination, disengage the PTO and do not run the pump. Start engine and warm it up for about 20-30 minutes, good and hot. Shut it down, then drain the old oil via the three drain plugs on the belly side -see drawing below. I use a large galvanized steel washtub placed underneath to capture all the old oil in. Next, start at the furthest most to the rear drain plug, on the diffy case -do not remove all three plugs at once. The drain has a Pipe Plug with a square head so you will need either a 9/16" open end wrench or if it hasn't been removed in quite sometime, may need to use a Crescent wrench with a breaker bar. You may need to reef on it some, but don't force it and certainly don't round off the square end or break it off. Let hot oil drain so while it's doing that, go do something else, like play with the dog or the wife or girlfriend; give it at least 20 minutes or so to drain. Next, move toward the front of tractor to the next plug, and bring the tub along too, located about in the center of the tractor underside. You will need a 1-1/6" wrench to remove the large hex head plug. You can use a good box wrench or a good socket wrench preferably a 6-point style. Note the plug has a gasket on it. You will need to remove all the old gasket material from the plug and the surface of the belly where it contacts. use a putty knife or old pocket knife and for stubborn pieces on the plug I just soak in a coffee can of gas while system is draining. After 20 or 30 minutes of draining, move the tub up to the final plug. If you go too far and remove the plug furthest to the front of tractor, you are removing the oil pan drain plug and you don't want to do that. You'll need the 1-1/16" wrench for that plug also. It takes the same drain plug gasket when reinstalling, p/n 8N-7011. You get them both in the new gasket set. The safety relief valve can be changed without removing the pump as well. You will need a stub length 11/16" open end wrench or take an old wrench and chop saw it off about 6" long. You reach in thru the side inspection cover openings to do that. Pretty basic stuff. The cam follower pin may need to be replaced as well so inspect that while top cover is off. If the system doesn't appear to have water contamination before you start, be sure to place the system in Draft Control, lever down, then get oil hot before draining and removing top cover.

 

[Model 660]

Wow! That's for the info. I've already drained the oil and it was black as can be so I'm thinking no water contamination. The pump seems to be tight , but the relief valve came out in two pieces. I've replaced or fixed the linkage on the lift cover and am going to get a cylinder and relief valve for it. I think I know the other site you speak of and will touch base with you there. Thanks

 

[JMOR]

(quoted from post at 08:32:09 03/06/17) Wow! That's for the info. I've already drained the oil and it was black as can be so I'm thinking no water contamination. The pump seems to be tight , but the relief valve came out in two pieces. I've replaced or fixed the linkage on the lift cover and am going to get a cylinder and relief valve for it. I think I know the other site you speak of and will touch base with you there. Thanks

Two pieces". That is because it is two valves, a check valve plus an over pressure relief valve.