Changing Hydraulic Oil 500 Hours

[Tractor Pilot]

I bought my 1997 JD770 last year at 510 hours. A previous owner had the 500 hour service done by a local, independant tractor mechanic a year before I bought it. I noticed that the hydraulic oil was still red and I have since learned that that usually means that is the originial fluid put in at the JD factory when the tractor was built.

I called the mechanic and asked him if he put in new hydraulic oil when he did the 500 hour service. He said that he didn't because if it was not overheated and not dirty then it is okay to reuse. So he put the red/original hydraulic fluid back in along with a new hydraulic filter.

1. Do you agree with this mechanics position? Don't think I do. I'm going to change out the hydraulic oil. What say you?

2. How do you flush out the lines and cylinders on the model 70 loader? Do you undo all the lines and exercise the cylinders manually to force out the old hydraulic oil?

Bruce

 

[MF 1532]

I would change it out just for peace of mind . Lower the 3 point hitch , lower fel , have oil warm and drain . ( that is the way I do it , I 'm sure there are other opinions . )

 

[J_J]

As far as purging old fluid from cyl and lines, it will depend on the amount of work that you want to do.

Simple way is to drain the hyd tank and replace the filter and clean out any screens that may be in the tractor.

To purge lines and cyl's, lower the 3pt, that drains 3pt cyl.

Since all cyl fluid flows through the OUT port, just remove the OUT hose from the FEL valve and connect a hose from the OUT port and place in a bucket to catch the cyl and hose fluid.

Raise the lift arms to full up, that drains part of the lift cyl's,

Tilt the bucket up, that drains part of the tilt cyl's.

Shut engine off.

Move the joystick to lower the lift arms, and tilt the bucket. You may have to help the bucket tilt down. This will push fluid to the OUT port into the bucket

If you really want to, you can install an air fitting in the FEL IN port, and apply air, and blow out the main path all the way to the tank. The tank should be draining.

Re-install the FEL OUT port hose, remove the air fitting, install a new filter, replace the screens, screw in the tank/reservoir plug, and fill tank with the correct fluid, re-install the IN port hose..

Start engine and leave at idle. Then work the functions of all valves to purge the air from the hyd system.

If you have a gage, you can check the FEL relief valve pressure.

 

[Tractor Pilot]

I changed the hydraulic oil & filter and cleaned the screen today (565 hours). Great job done. I was able to jack up the tractor just enough to slide a 5 gallon bucket under the drain plug (JD770 holds 4 gallons of hydraulic fluid). After most of the fluid drained, I lowered the tractor and drained the remainder of the fluid into a smaller container. No mess.

I think that mechanic only changed the hydraulic filter at the 506 hour mark and called it "good." Both drain plugs and the three bolts for the hydraulic screen cover still had untouched, virgin John Deere paint on them. The hydraulic screen was 99% clean, but there were a some fine metal shavings on one end of the screen. I suspect the metal filings were probably left over from the manufacturing process or during the break-in period back in 1997 when the tractor was new.

Thanks for the advise, J_J. But I ended up doing it "the simple way."

 

[statenst]

I have a 1999 MF 271 with Loader, I have change out the joy stick controler, and have filll the hydraulic oil rev. Now the power stering acts as if it has air in it. I think i need to change or clean the hydraulic oil screen. The loader is having the same problem. Is the screen on the right side under the foot rest on the suct. line to the pump?