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Why Won’t My Hydrostatic Lawn Mower Move?

A hydrostatic mower has a hydraulic pump with a hydraulic motor. It uses hydrostatic transmissions to mow through a wide range of speeds. The hydrostatic transmission helps it transmit the power from the engine to the drive wheels without using gears or speed reducers. 

The movement or displacement in fluid pressure is used to control the speed and torque transmitted to the output shaft, which turns an axle, gear, chain sprocket, belt pulley, or other device. 

Hydrostatic mowers are great for cutting grass but sometimes they can get clogged and won’t move. Let’s find out the possible reasons and fix the issues.

A hydrostatic lawn mower
A hydrostatic lawn mower

Reasons why won’t hydrostatic mower move

When there is old hydraulic fluid in the lines, the mower won’t move because it can’t send pressure to the wheels. When there is air in the lines, it will be tough to push and pull levers on the handle that control how fast or slow you go. 

A worn drive belt will cause a hydrostatic mower not to work as efficiently as it should and will cause you to have lots of downtime due to repairs.

Low Hydraulic fluid

Low hydraulic fluid is a problem with hydraulic lawnmowers. Low hydraulic fluid can lead to overheating and increased friction, which in turn can cause the engine to seize.

Low hydraulic fluid is typically caused by leaks in the hydrostatic system where the fluid escapes from the tank to ground level, or when a hydraulic hose has been disconnected from one of its fittings or valves. 

Moreover, a lawnmower with a bad hydraulic fluid will have a hard time mowing the lawn. To prevent this from happening, it’s important to regularly check and maintain your hydraulic fluid levels. 

If you notice that your mower is moving slower than usual, or that it sounds louder than before, then you should contact your local repair dealership immediately.

Old hydraulic fluid in the lines

Hydraulic fluid is pressurized oil that is used to transmit power from the engine to the wheels of the lawnmower. When fluid sits for a long time, it can form sludge and varnish that clog passages in the system. 

This prevents the transmission from being used efficiently. Flushing this sludge or varnish out of these passages will restore efficient use of the transmission. 

Hydraulic fluids are not designed to sit for a long time. Newer hydraulic fluids have additives that prevent the fluid from breaking down and stop it from thickening.

Drive release handle is set incorrectly

Hydrostatic mowers are designed for easy maneuverability. Not only are they lightweight, but they also have a drive release so the mower can roll free. 

With hydrostatic mowers, there is no need to twist or pull your lawnmower backwards to release the drive. This is helpful when your mower has gotten stuck, and you need to push the zero turn onto a trailer.

The drive release handle comes in the form of a lever, push/pull button, or knob. The function of this part is to help mowers move. 

When you press on the release, keep in mind that you should release the mower and allow it to roll free in the “operating” position.

Air has clogged in the Lines

A common problem of riding mowers is lack of movement due to the air clogging the lines. The hydraulic oil inside the machine cannot flow properly and thus, will not be able to push on the ground under the mower. 

A quick fix to this problem is to empty your mower of hydraulic oil after the season and then let it run for a few minutes until all air has been expelled from the lines.

If you are not sure how to do this, consult with a professional about how to do so. When you are storing your lawn mower for the winter, it is important that the vehicle has enough pressure in its lines. This will ensure that your mower can start up next spring without any issues.

It is a good idea to bleed all the air out of the system before attempting to mow a lawn. The operator’s manual for your specific model should also come in handy for correct procedures for removing air from lines.

If someone fails to do this step, they may be unable to move their mower as there will still be some air in gas lines.

The operator’s manual for your specific model should also come in handy for correct procedures for removing air from lines.

Faulty tensioner pulley

A faulty tensioner pulley on your lawn mower can prevent it from moving. It is made from a hard plastic with a bearing in the center. The pulley can break, and the bearing inside can fail. So, check your pulley and replace it when needed.

Tensioner pulley of a lawn mower
Tensioner pulley of a lawn mower

Broken ground drive belt

A drive belt is a belt that transmits power from the ground drive pulley to the mower’s engine. When a drive belt breaks, it can lead to a variety of problems for your lawnmower.

A broken ground drive belt can prevent your mower from moving. This will happen when you turn on the mower and it’s slow and sluggish, or if you hear a high-pitched squeal. 

If this is happening, you won’t get any movement out of your lawnmower because it needs that power input to start up.

A worn drive belt may be the reason for this issue as well because if the ground pulley is not turning, then there’s nothing getting to your engine. So, nothing will happen at all.

To fix a broken ground drive belt, one needs to identify the location of the belt and determine whether it needs to be removed.

One can usually tell if a belt needs to be removed by looking for objects that may have caught on the belt and jammed it, such as sticks, stones, dirt clumps, or leaves. 

Next step would be removing any obstacle that may have caused the ground drive belt breakage.

Faulty pressure switches

Faulty pressure switches can also prevent you from being able to move your lawn mower. These sensors are responsible for the seat’s ability to register that someone is sitting on it. 

This means that if your pressure sensor is faulty, you cannot get the lawn mower moving. The result of this would be an immobile mower and you would have to restart it manually every time you want to use it.

testing a faulty pressure switch of a lawn mower
Faulty pressure switch of a lawn mower

A faulty pressure switch will not be able to detect the correct function, which means that the machine will not be able to work properly. 

If you think that your pressure switch might have gone faulty, then you should try inspecting the sensor.

You must inspect the sensor to make sure it hasn’t been damaged. Inspecting the sensor should be done by removing it from its mounting hardware and looking for obstructions or damage to the sensor. 

You may want to replace your chair and try to get help from professionals.

Leakage of hydraulic fuel

A fuel leak in the hydraulic system is one of the most common reasons for mowing machine stoppages. It can be solved by inspecting and replacing worn or incorrect parts.

Improper design and selection of components are also among top reasons for machine stoppages related to hydraulic systems. Poorly fit connections, improper installation, lack of proper lubrication. 

Also, contamination with dirt or debris are some other common causes for this issue.

One of the most common causes of a hydraulic fuel leak is the carburetor. The vent hole in the carburetor must be open and unobstructed for air to flow properly. 

This is necessary to create an air-fuel mixture for combustion to occur. Hydraulic fuel leaks are not only environmental hazards but also put the consumer at risk. 

A hydraulic fuel leak can be easily fixed by installing accumulators and shock suppressors on to the system. These two parts help to reduce any pressure fluctuations in the system.

Thus, preventing any losses in power, which would cause a hydraulic fuel leak. You might also need you replace the broken gasket seals, and repair or replace the crankcase gasket. Also, you need to fill your lawn mower with enough hydraulic transmission.


It is important to keep your mower running in top condition if you want it to last. The most important thing to do is to replace the engine oil, oil filter, air filter, fuel filter and spark plug. 

You should also make sure that you are checking the ignition, carburetor, battery, and throttle. You should also keep the engine oil at the appropriate level for an extended period, change the oil filter and air filter as needed, replace fuel filters and spark plugs on a regular basis.

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