How to add hydraulic fluid to the pumps?

Maintanance - How to purge Hydraulic drive system Published 01/13/2010 11:56 AM ' Updated 06/02/2015 02:52 PM
How do I purge the hydraulic system?
Hydrostatic transmissions use oil, under pressure, to provide movement for the tractor. The fluid is pressurized with a pump inside the transmission. If any air is in the fluid, the pump will try to pressurize air. This condition is known as cavitation, and is detrimental to the pump since it allows the pump top operate dry. When the pump cavitates it is not pressurizing any fluid, so the transmission is not able to provide the movement needed.
If your mower is new, or has been stored for a long period (longer than 2 months) the transmission needs to be purged before use. Also, if you experience loss of drive, or slower response, then the transmission should be purged first.
The following procedure will remove trapped air inside the transmission(s).

IMPORTANT: SHOULD YOUR TRANSMISSION REQUIRE REMOVAL FOR SERVICE OR REPLACEMENT, IT SHOULD BE PURGED AFTER REINSTALLATION BEFORE OPERATING THE TRACTOR.
Step 1- Place the rear of the mower safely onto jackstands on a level surface with engine off and parking brake set.

Step 2- Disengage transmission by placing freewheel control, located at the back of the frame, in the freewheeling position.

2a- Mowers with seperate pumps and wheel motors the freewheel is activated by turnign the bypass valves, one on each pump, two full turns.
The oil resevoir needs to be filled to the specifications listed in the owners manual before starting the purge procedure.
Step 3- Sitting in the operators seat(riders), start engine. After the engine is running, move throttle control to slow position. With motion control levers in neutral (N) position, slowly disengage clutch/brake pedal.
Step 4-Move motion control levers to full forward position and hold for five (5) seconds. Move levers to full reverse position and hold for five (5) seconds. Repeat this procedure three (3) times.

NOTE: During this procedure there may be some movement of the drive wheels, but they are not under load. The air is being removed from hydraulic drive system.

Step 5-Move motion control levers to neutral (N) position. Shutoff engine and set parking brake. Check and add oil as needed for units with an oil resevoir.

Step 6-Engage transmission by placing freewheel control into driving position, or by closing the bypass valves on the pumps.
Step 7-Sitting in the operators seat, start engine. After the engine is running, move throttle control to full speed. With motion control levers in neutral (N) position, slowly disengage clutch/brake pedal.

Step 8-Slowly move motion control levers forward, after the tractor moves approximately five (5) feet, slowly move motion control levers to reverse position.
After the mower moves approximately five (5) feet return the motion control levers to the neutral (N) position. Repeat this procedure with the motion control levers three (3) times.

Step 9-Your mower is now purged and now ready for normal operation.For further information or assistance, we recommend contacting your lo

First off, riding mowers do not "go into gear"; nor can they be shifted into or out of gear...nor, as a matter of fact are they "automatic" or do they have "automatic" transmissions. Instead, the so-called hydrostatic "transmission" is nothing more than the sense one gets--encouraged by mfr/seller misdirection (or product ignorance)--that a mower works just like a car...rather than being powered by nothing more than a belt that turns a wee little hydraulic motor, the speed and direction of which is controlled by the foot pedal controlling volume of fluid coursing though it to hydraulically drive the drive wheels.

If your rider will not move, that means one of two things (other than fatal failure mode)...or rather two of one thing, the latter being that hydraulic fluid it not flowing, is not pumping freely, through that motor.

Reason 1 (the more likely) is that the manual-mower-push switch on the motor has been engaged to permit the mower to be pushed without the vehicle (drive wheels) being blocked...because the engine is not running, so the fluid cannot flow with the turning of the drive wheels (unless the switch is engaged).

Think of it this way. When the mower is running and the clutched engine PTO is driving the belt or shaft that drives the hydraulic motor, the direction is chosen by reversing direction of fluid flow that the motor is circulating under pressure (also called pumping) to the drive wheels. Push toe and it flows and drives wheels in the mower-forward-drive direction; push heel and it flows the other way. Now, what about when neither is pushed? Then, essentially, all channels of flow are blocked--"neutral" (if you want to think of it that way) is not freewheeling (as with a car), it is drive wheel blocked by hydraulic lock at the motor. That is why a "hydo..." equipped mower does not coast as does a car. Alternatively, suppose that you could lift up and try to rotate the drive wheels in a particular direction. You would find that the wheels resist turning (unlike rotating RWD car drive wheels to remove a drive shaft, for example)...because they are essentially hydraulically locked by the motor that is not allowing compensatory fluid circulation in any direction!

Now, to disable the manual push mode that allows the drive wheels to rotate for manual pushing, look under the mower at the drive motor. It will be at the end of the belt loop or shaft being driven at the PTO beneath the engine. Now, find some kind of protruding lever big enough to grasp. If it seems "up" push it down; if "down" push it up...just make it go the other way to release. Now, start up and drive the mower normally. But wait! Before you mow, read the below.

Reason number 2 for unexpected drive wheel drive failure is absence of fluid to drive them....because you have not check fluid level and maintained it as the instructions directed you to do. So find the fluid plenum/level-check container and add some fluid if it is low. Just a little. Then start the engine and check lever with motor running. Fill carefully to indicated level but be very careful not to over fill. The mower should now run with valuable maintenance lesson learned. And remember that neglected fluid check can greatly shorten hydraulic motor life. Oh, make sure to check fluid level again when finished....after any air has been purged...add if/as necessary.

there should be a single reservoir for the main drive motor that supplies fluid under pressure to the drive motors at the wheels . Check that level and if ok then the problem will be in that drive motor and it may need repairs.

Check your fluid level, how long since filter change

overfill it just a little make sure transmmision is engaged run for 30 minutes see if it will move if not bad hydrio pump

The rear windows are controlled by a timer in the top's ECU. If
the rear windows stop fully closing before your top is closed, the
problem MAY be with top's hydraulic system.

Check your top's hydraulic reserve tank for low fluid level. Lack
of fluid will greatly delay the top's closing sequence, leaving
those rear windows partially open.
Your top's hydraulic pump system is located beneath the right side
of the cubby/storage box behind the front seats. Raise the cover
and you'll see a removable trim panel on the right side. The pump
is behind that access panel.

You can use power steering fluid to top off the tank, but don't
fill it above level indicator line. You may have to add more fluid
after you cycle the top up and down to get the air bubbles out of
the lines.
It could also be a relay. On a 95 the relays that are in the trunk above the battery.
Perhaps, just switching the relays might prove which one is failing..

Your yardman mower is a hydrostatic model which uses a small hydraulic pump to turn a hydraulic drive motor.Check there is sufficient oil in the transmission. Check the forward/reverse lever travel, and adjust as needed to increase the "throw" to move the swashplate in the hydraulic motor.

raise front loader....loosen hyd. line a little lower loader till all air is released and only fluid is coming out and retighten.....its like bleedig brakes on a car

Hydraulic fluid straight from the drum, has a typical cleanliness level of ISO 4406 21/18. A 25 GPM pump operating continuously in hydraulic oil at this cleanliness level will circulate 3,500 pounds of dirt to the hydraulic system's components each year! To add hydraulic oil, and not the dirt, always filter new oil prior to use in a hydraulic system. This can be accomplished by pumping the oil into the hydraulic reservoir through the system's return filter. The easiest way to do this is to install a tee in the return line and attach a quick-connector to the branch of this tee. Attach the other half of the quick-connector to the discharge hose of a drum pump. When hydraulic oil needs to be added to the reservoir, the drum pump is coupled to the return line and the oil is pumped into the reservoir through the return filter. As well as filtering the oil, spills are avoided and the ingress of external contamination is prevented. The benefits of carrying out this simple modification are well worth the minor cost involved.

1. Drive the vehicle until the fluid temperature reaches normal operating the usual temperature [80-90°C (176-194°F)]. 2. Place the vehicle on a level floor. 3. Move the selector lever sequentially to every position. This will fill the torque converter and hydraulic system with fluid, then place lever in "N" (Neutral) position. 4. Before removing the dipstick, wipe all contaminate from area around the dipstick. Then take out the dipstick and check the condition of the fluid. The transaxle should be overhauled under the following conditions. a. If there is a "burning" odor. b. If the fluid color has become noticeably blacker. c. If there is a noticeably excessive amount of metal particles in the fluid. 5. Check to see if the fluid level is in the "HOT" range on dipstick. If fluid level is low, add automatic transaxle fluid until the level reaches the "HOT" range. Transaxle fluid: GENUINE HYUNDAI ATF SP-II, DIAMOND ATF SP-II or AUTRAN MMSP-II. Low fluid level can cause a variety of abnormal conditions because it allows the pump to take in air along with fluid. Air trapped in the hydraulic system forms bubbles which are compressable. Therefore, pressures will be erratic, causing delayed shifting, slipping clutch and brakes, etc. Improper filling can also raise fluid level too high. When the transaxle has too much fluid, gears churn up foam and cause the same conditions which occur with low fluid level, resulting in accelerated deterioration of automatic transaxle fluid. In either case, air bubbles can cause overheating, and fluid oxidation, which can interfere with normal valve, clutch, and servo operation. Foaming can also result in fluid escaping from the transaxle vent where it may be mistaken for a leak. 6. Be sure to examine the fluid on the dipstick closely.