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I followed the manufacturer's instructions for changing the hydraulic oil including a new filter. I followed the instructions by putting it on jack stands and letting it run.
It run fine on the jack stands but when I take it out in the yard, I can barely get it to move. I need to figure this out. I'm getting frustrated.
Thanks for any help!

say a prayer & take your time while on jack stands, it may take quite a few cycles of going slow in forward & reverse & moving up your throttle gradually, check fluid level often while bleeding air from system while operating controls, having a helper watching fluid level will help.

Here is my a picture of my hydraulic pump. There are two of them. They each have a bypass valve, it is the 5/8's bolt you see at the top. This one turns easy, the other side is very hard to loosen and tighten. Shoyld I have these a little open when running it on jack stands?
Thanks for your help.

Typically while bleeding/purging the system you would not do anything with the bypass valves. In fact, the only time you would even use them on a ZTR is if you had to push or tow your mower due to a hydrostatic motor failure or if you needed to move it when the engine was not capable of running.

cruzenmike said:

Typically while bleeding/purging the system you would not do anything with the bypass valves. In fact, the only time you would even use them on a ZTR is if you had to push or tow your mower due to a hydrostatic motor failure or if you needed to move it when the engine was not capable of running.

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Ok, thanks. I will let you know how I make out. You have been very nice to help me.

denisp said:

Ok, thanks. I will let you know how I make out. You have been very nice to help me.

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I have another question. My mower is I guess pretty old. The manual tells me to use only SAE 10W40 SG, SF/CC, CD service motor oil.
And add 1/2 unit (approximately 3.5 oz.) of Lubrizol additive. One dealer told me that they don't add it anymore. I used 15W40 CJ3 motor oil. It is not synthetic, is this correct? Could the grade of oil make a difference in how it operates right after you change it? I know oil breaks down, but not that fast. Should I have gone with a synthetic oil?
Thanks,
Denis

Purging Air from Hydraulics
1. Raise rear wheels off ground. Brace with jack stands.
2. Put bypass valves so it freewheels.
3. Get on mower start it and release the brake.
4. Push drive lever full forward for 10 seconds the full reverse for 10 sec. Do this 10 times for forward and 10 times for reverse alternating between each.
5. Return levers to the parked position and set brake. Turn off the mower. Move bypass valve bake to normal operation.
6. Get back on the mower and start it. Do step #4 again.
7. Return levers to the parked position and set brake. Turn off the mower.
8. Return mower to ground.
9. Test for proper working. If not repeat.
10. Check oil level and fill.

BlazNT said:

Purging Air from Hydraulics
1. Raise rear wheels off ground. Brace with jack stands.
2. Put bypass valves so it freewheels.
3. Get on mower start it and release the brake.
4. Push drive lever full forward for 10 seconds the full reverse for 10 sec. Do this 10 times for forward and 10 times for reverse alternating between each.
5. Return levers to the parked position and set brake. Turn off the mower. Move bypass valve bake to normal operation.
6. Get back on the mower and start it. Do step #4 again.
7. Return levers to the parked position and set brake. Turn off the mower.
8. Return mower to ground.
9. Test for proper working. If not repeat.
10. Check oil level and fill.

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Does it matter if it is 15w/40 or 20/w50?

denisp said:

Does it matter if it is 15w/40 or 20/w50?

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Yes, a thinner oil will not build the pressure needed to drive the motors.

Thank you everyone.
I changed the oil again. And I used the purge procedure last described.
I don't know if it worked, it will have to wait until next Saturday.
It will give it a chance to sit a rest like me!

Thanks again!

denisp said:

I followed the manufacturer's instructions for changing the hydraulic oil including a new filter. I followed the instructions by putting it on jack stands and letting it run.
It run fine on the jack stands but when I take it out in the yard, I can barely get it to move. I need to figure this out. I'm getting frustrated.
Thanks for any help!

Click to expand...

I had the same problem and read in this forum that the covers on the bottom of the pump, that has 2 screws holding it on, which I took off to replace a leaking seal was turned around. I didn't believe this could be the problem, but once I turned them around the directions for bleeding the pump worked perfectly. If you didn't take those caps off then get a socket torx , allen or hex driver and loosen the top plug on the pump and fill with oil until it runs out, then put the plug back in and purge the pumps being jacked up.

The seals will leak inside the pump under the cap and is easy to replace as long as you don't strip anything or get the cap on wrong, also frequently go around the entire pump tightening all the bolts.