Zero Turn Hydraulic Pump Troubleshooting (Guide & Solutions)

A common failure for zero turn mower is the hydraulic pump. If the hydraulic system fails, the mower won’t get enough power to move. Finding out the source of the problem is a challenge in terms of these failures. 

That’s why it’s important to know the steps of zero turn hydraulic pump troubleshooting. You need to purge the hydraulic drive system and check other parts and symptoms. 

Now, scroll down the article to know more how to troubleshoot the zero turn hydraulic pump.

Common Causes For Zero Turn Hydraulic Pump Failure


The most common problem with a Hydraulic pump is the mixture of water and air. Very often, the pump becomes full of air instead of oil, and as a result, it cannot generate enough pressure needed to provide power. 

This problem is commonly known as capitation. This is quite common with zero-turn. 

When you store the mower in winter, purging the transmission before use is a good practice to solve this cavitation problem. It will also help in terms of a sluggish or slow mower. 


Aeration is also another common cause of hydraulic pump problems. It occurs when air enters the pump cavity from outside. 

Loose connections or leaks can be responsible for this. Aeration creates a knocking sound when the pump is running.


The temperature problem can be explained twofold. If the zero turn mower runs too cold or too hot, it can engender serious problems over time, such as preventing lubrication by making the mower out of hydraulic fluid. 

It can also result in the oxidization of fluids. All these restrict the flow of oil to the pump. Another thing is the temperature of hydraulic fluid. If it’s too high, it can easily get contaminated, making the oil stale and defective.  

Oil Level and Quality

The oil level is very important for the hydraulic pump to work with full efficiency. Low oil levels can create various problems in your mower. So you should always keep the mower filled with pure, clean recommended oil.

Troubleshooting Hydraulic Pump Problems

Purge The Hydraulic Drive System

As I’ve told you earlier, purging the transmission before use after storing the mower for a long time is a good idea. First, let us see how to purge the air from the system. 

  • First, park the mower on an even ground setting the parking brake. Keep the rear on jack stands.
  • Now disengage the transmission and sit in the operator’s seat to start the engine. If you are wondering how to disengage the transmission, go through the operator’s manual.
  • Keep the engine running. And move throttle control to slow position and position the motion control lever should be positioned in neutral. Disengage the clutch. 
  • Push motion control levers to the full forward and hold them for five seconds. Now do the reverse. Repeat this 3-5 times. It will help purge the air from the hydraulic transmission system.
  • Put the control levers in neutral and shut the engine off. Engage the transmission and remove the mower from jack stands. 
  • Start the engine and disengage the brake.
  • Finally, move the control lever forward and move about 5 feet. Then slowly reverse the same distance. Return the lever to neutral. Repeat these final steps 3-4 times. 

You are all done!

Check The System

However, only purging may not help every time. That’s why it’s important to have a check on the system to troubleshoot other problems. 

  • The very first thing you should check is the Pressure Release Valve. Make sure that the valve is in the drive position. 
  • Check if the motor has correct wiring and whether it is making any unusual sounds.
  • Carefully examine the internal parts of the pump to see if they are installed properly and functioning accordingly. Install them in the recommended way and replace the defective parts.
  • The hydraulic oil or fluid is the most crucial part of the pump. Check if the oil level is right. Also, make sure the oil is clean and has the recommended viscosity. Keep in mind that all oil is not appropriate for zero turn mower. Change old and sluggish fluids. 
  • Check the lines and connections for possible leaks. Reconnect them if there is no leak and repair the leaks otherwise. Leaking can dry the oil reservoir up. So, make sure there are not any. If it still doesn’t work, you should replace the hydro components.

How to Prevent Hydraulic System Failure?

Once your hydraulic pump fails, its lifespan can become less even if you can fix the problem. That’s why it’s better to maintain the hydraulic system regularly. It will help a lot in terms of the longevity of the pump.

Check the oil level, connections, and hoses every day so that you can catch any problem instantly. It will prevent the build-up of bigger issues.

The common failure places or causes like filters, components should be in regular check and maintenance.

Finally, you can use an infra-red thermometer to keep the temperature in check. It will make the inspection easier by showing the hotter or cooler portion of the mower in color gradient. 

Do Hydrostatic Transmissions Wear Out?

Yes, hydrostatic transmissions are prone to frequent damage. Actually, these transmissions are not made for higher efficiency. 

That’s why they produce more heat to do the same amount of work as their counterparts. This extra heat shortens their lifespan. So, they wear out with time.

What Kind Of Hydraulic Fluid Do I Need For A Zero Turn Mower?

There are some specific types of fuel you have to use for a Zero Turn Mower. Different Zero turn mowers have different recommended oil. 

For instance, you should use the hydraulic fluid produced by Toro for their mowers. 

You can also use Mobil 424 Hydraulic fluid. Check the manual to know the recommended oil type for a mower.

Final Words

Now do you know about zero turn hydraulic pump troubleshooting? 

Always keep in mind the problems of cavitation, aeration, improper temperature, wrong oil and others. Let us know if you are benefitted by our tips.

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