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I have 2 Hydro-Gear pumps on a Ferris Z 3100. Drove into garage to work on motor and now it won't move. Changed the hydro filter and fluid. The bypass valves are closed. Is there a need to bleed these pumps before they will pump? If so,how is it done? thanks, gregjo1948

If you changed the oil in both pumps you will have to remove the air trapped in the system. This is how I do it and I warn you this may take some time. Minimum of two hours unless you get real lucky.

1. Block both front wheels so the unit can’t roll forward.
2. Jack up the rear end and put on jack stands so the wheels are at least 2” off the floor.
3. Start up the unit and push the sticks forward about halfway and hold for 30 seconds.
4. Bring sticks back to neutral and let it run there for 30 seconds.
5. Pull back on the sticks about halfway and hold for 30 seconds.
6. Bring sticks back to neutral and let it run there for 30 seconds.
7. Repeat steps 3-6 a half dozen times.
8. Shut off unit and let it sit for 15-20 minutes.

During these steps the wheels should be turning slowly, but may turn faster as you go through each cycle. I have had units which the wheels don’t start turning until the fifth or sixth cycle.

9. Repeat steps 3-8, but this time move sticks to full travel and hold for 1 minute.

If you are lucky your wheels should be turning much faster. If they do not turn faster repeat step 9. Now is when you need patience. Why? Depending on how much air is in the system, you may have to going through the steps 5-10 times before you get all the air out. It will be helpful if you have an assistant who can put his foot on the wheels to see if he can stop the wheels from turning. I’ve had a couple of units I’ve had to let the unit sit over night and repeat the steps the next day, because I couldn’t get it to push out all the air.

10. Now that your wheels are turning fast and you can’t stop them, cycle 6 times through left and right turns at all speeds.

If everything looks good, drop the unit off the stands and test the unit.

REMINDER: KEEP YOUR EYES ON THE FLUID RESERVOIR OR FLUID HEIGHT, AS YOU MAY HAVE TO ADD EACH TIME YOU SHUT THE UNIT OFF. LOW FLUID WILL RESULT IN POOR OPERATION. AS YOU REMOVE AIR WHO NEED TO REPLACE WITH FLUID.

There are other ways to do this, depending on your equipment, but this is how I do it. Also, not uncommon for one pump having more air than the other, so you must keep checking both each time.

Forgot to ask; did you use the fluid recommended by the manufacturer? If not, this could add to the problem.

Good Luck, have PATIENCE.

Thanks Rivets. Always open to learning different techniques.

If you're looking into Hydro-Gear pumps, they’re pretty solid overall. They’re known for their durability and are used in many commercial-grade equipment, which says a lot about their reliability. I’ve worked with them a few times, and I like how smoothly they run when adequately maintained.

Of course, regular checks are key – ensure you’re keeping them clean and debris-free. If you plan to replace one or install a new system, it’s always a good idea to check the specs carefully. For more in-depth information, you could also check out gear pumps to understand how they work in various setups. They do an excellent job for the price and are pretty easy to troubleshoot.

gregjo1948 said:

I have 2 Hydro-Gear pumps on a Ferris Z 3100. Drove into garage to work on motor and now it won't move. Changed the hydro filter and fluid. The bypass valves are closed. Is there a need to bleed these pumps before they will pump? If so,how is it done? thanks, gregjo1948

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Of course you have to go through the purging process. Just like with a brake system, no air can be in the system.

I apologize because I’m a rookie at this and learning as I go. I have done a bit of small engine repair but the hydro-gear transmissions are foreign territory to me.

I have a Scag 48” Liberty-Z with approximately 300 hours. I just changed the hydro-gear filters and fluid because I never changed it since owning the mower and the control handle was slow to return when I started it up for the spring and that’s when I noticed the reservoir was empty.

I figured that part out, the reservoir tank has a small crack with a slow leak so I have a new one on order.

My new issue is that I have no power to the right wheel when the bypass is closed and for some reason when the bypass is open, the left wheel still has power. I followed the purge instructions, the belts all seem to be in good condition and not loose, oil is level is good, and there are no weird noises. I did have power to both wheels prior to the oil change.

Do I continue the purge process? Any suggestions before I throw in the towel and pay to have it serviced are appreciated.