Toro Zero Turn Hydraulic Problems

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Compared to typical lawn mowers, the Toro Zero Turn mower has a different transmission and hydraulic system. As a result, it is vulnerable to several specific hydraulic problems.

In this article, I discuss 7 common Toro Zero Turn Hydraulic problems and simple DIY troubleshooting tips to diagnose and fix these problems respectively.

Toro Zero Turn Hydraulic Problems, Causes, and Possible Solutions

Before I go into details, let’s have a quick look at some common Toro zero-turn problems and their possible solutions. Also, it is important to note that this is one of the common Toro mower problems.


Possible Solutions

1. The hydrostatic transmission will not move
  • Engage the hydrostatic motors
  • Top up/replace stale hydraulic fluid
  • Replace the drive belt
  • Inspect the pulley spring and pulley tensioner and replace them if damaged
  • Purge the system to remove air bubbles
2. Turning issues
  • Check tire pressure and inflate deflated tires
  • Replace bad dampers
  • Replace worn belts and pulleys
3. Transmission leak
  • Tighten every loose connection
  • Look for broken hoses and seals and replace them
  • Purge the transmission system
4. One side not working
  • Inflate lessened tires after checking the tire pressures
  • Purge the system
  • Replace worn belts
  • Remove any extra weight on the mower
  • Replace clogged hydro oil filters
5. Overheating system 
  • Replace contaminated/stale hydraulic fluid
  • Top up the fluid level if it is low
  • Replace blocked/damaged heat exchanger
6. Too cold hydraulic system 
  • Anticoagulants should be added to the transmission fluid
  • Find and replace the source of the leakage
7. Hydraulic pump failure 
  • Disassemble the pump and replace failed components
  • Replace the pump if severely damaged or worn

1. Toro Zero Turn Hydrostatic Transmission Will Not Move

One of the common toro zero turn hydrostatic transmission problems is that your mower won’t move. The most frequent cause of hydrostatic failures is stale hydraulic fluid.

Hydraulic oil becomes contaminated over time by air and moisture, losing its purity. Compared to fresh oil, this older oil has poorer hydraulic qualities and may result in a lack of movement.


  • Disengaged hydrostatic motors
  • Old hydraulic fluid 
  • Low fluid level
  • Slipping drive belt
  • Damaged pulleys
  • Aeration


The motor should be checked first. You can disengage the transmission by using the release pin located at the back of the lawnmower. 

If you ever need to work on the mower without it moving, this feature will come in handy. Check the motor disengagement hoop/lever and re-engage it.

Next, check the hydraulic fluid. Drain and refill if it is stale or appears to be dark red. Change the fluid after every 1000 hours or as recommended by your manufacturer.

Check your hydraulic oil periodically to ensure your hydraulic fluid is full, and top it up when necessary.

The hydrostatic pump relies on the belt to transfer power and enable movement. Check the belt’s tension and overall condition. It must be replaced if you discover it to be slack or damaged.

Cavitation, often known as the formation of air bubbles, can occur when air enters the system due to a leak in the system or from hot hydro oil. Bleed or purge the system to get rid of trapped air.

2. Turning Issues

Your Toro Zero Turn hydraulic mower may experience turning issues. It may become hard to steer or refuse to turn in a certain direction.

You may also be unable to drive the mower in a straight lane due to hydraulic turning problems.


  • Uneven tire pressure
  • Bad dampers
  • Worn/damaged belts


Your Toro zero turn may have turning issues if the tire pressure is uneven. Your lawnmower’s tires need to have the same pressure on both sides to enable it to turn and drive correctly.

Check the recommended PSI (minimum tire pressure) for your mower. Inflate the tires to the recommended PSI using a tire pump.

Your mower will jerk to one side when moving forward if the dampers are bad. Check the dampers and replace them with new ones if they are damaged.

Also, inspect the belt and replace a glazed, slipping, or torn belt.

3. Toro Zero Turn Transmission Leak

Your zero turn’s hydraulic fluid may seem to run out quickly or you may notice oil stains near the transmissions.

This indicates that there is a leak in the system. A transmission leak may also cause air contamination and movement issues in your Toro Zero Turn.


  • Overheating
  • Broken hydraulic hoses and seals
  • Loose connections


Hoses and seals may break when using hydrostatic transmissions because of the extreme pressure and heat they are subjected to. 

Check for broken hoses and seals. Look for any potential leaks in every line and replace them if found. 

A loose connection can induce a leak that will drain the system sufficiently to become a problem over time. Tighten every connection and component.

The oil reserve will eventually run out if there is a leak anywhere. And air may enter, slowing down the mower and perhaps causing it to stop after a while. 

Fill up the transmission with hydraulic fluid and purge the system after replacing the leaking component.

4. Toro Zero Turn One Side Not Working

Another typical issue with these mowers is that one side becomes weak. A riding mower that is continuously tugging to one side can be quite exhausting to drive.


  • Insufficient tire compression on one side
  • Airlock in the hydrostatic motor
  • Lack of traction on one side
  • Inadequate weight balance
  • Clogged hydro oil filter 


First, check the tire pressure on each tire and inflate lessened tires to the recommended tire pressure in your owner’s manual.

Purge the system to get rid of air that could be causing it to drag to one side. Then, check the belt and pulley system.

A slack belt or damaged pulleys can cause reduced traction on one side. Replace damaged belts and repair any bad pulleys.

Remove any extra weight on your mower that may be putting extra pressure on one side. Top up the hydraulic oil and replace the oil filter if it is dirty or clogged.

5. Overheating Hydraulic System 

If your Toro Zero Turn hydraulic system runs too hot or too cold, it can cause major issues over time. 

A system that is overheating may cause hydraulic fluids to leak out, impede lubrication, and wear out system parts. These will eventually limit oil flow and make it more difficult for oil to reach the pump.

Causes Of Overheating

  • Contaminated/stale hydraulic fluid
  • Low fluid level
  • Aeration
  • Blocked/damaged heat exchanger


If the hydraulic oil is stale, bleed the system and replace the oil with fresh fluid. Top up the oil level if it is low.

Seals and fittings can break and result in air entering the system and creating bubbles in your fluid. Your system compresses air bubbles, which produce heat. Purge the system to get rid of air.

The heat exchanger is an essential part of your hydraulic pump’s cooling system. If it gets blocked or damaged, then it cannot help remove heat from your pump properly.

Have a hydraulic system repair expert examine the heat exchanger to determine if it needs repairing or replacing.

6. Too Cold Hydraulic System

The hydraulic system in your Toro Zero Turn is at risk if it becomes overly cold. Due to the cold, hydraulic fluid thickens and becomes unable to reach the pump.

The hydraulic system’s capacity to dissipate heat will also deteriorate, which will impair the transmission system.


  • Air contamination
  • Leaks in the hydraulic system


Anticoagulants should be added to your transmission fluid to prevent it from getting too thick.

Look for potential air contaminant sources, fix or replace them, and then purge the system.

Visit the closest mechanic shop if the issue continues to prevent further harm.

7. Hydraulic Pump Failure

The transmission pump’s efficiency decreases after many years of use. Its ability to quickly supply pressure decreases with age, which has an impact on the vehicle’s ability to shift.

In most cases, shifting difficulty or, in the worst-case situation, complete movement failure will be noticeable.


  • Hydraulic pump wear
  • Fluid/air contamination
  • Faulty installations
  • Incompatible parts
  • Improper maintenance


Disassemble the pump assembly and check each component to make sure it is in good working order and that it was installed properly. The pump shaft, connection, and filter are the most frequently encountered trouble spots.

Replace faulty parts or replace the pump if it is worn or damaged.

Performing regular maintenance will help prolong the life span of your hydraulic pump.


Problems frequently encountered with the Toro Zero Turn hydraulic system include turning issues, movement issues, transmission leaks, overheating, too-cold transmission, and hydraulic pump failure.

Follow the troubleshooting guides in this article to fix your hydraulic system problems. Keep in mind that the majority of these problems can be avoided by performing regular maintenance.

Frequently Asked Questions 

1. Do Hydrostatic Transmissions Wear Out?

Yes, hydrostatic transmissions wear out over time and with frequent use.

2. What Kind Of Hydraulic Fluid Goes In A Toro Zero Turn Mower?

The application of the right type of hydraulic fluid for the Toro Zero turn is critical. Toro manufactures high-quality hydraulic fluids for use in its product line.

3. How Will I Know If My Transmission Fluid Needs To Be Changed?

You will know when your transmission fluid needs to be changed by the color change. The new fluid is bright pink. Once the fluid loses its pink shade and turns brown, it needs to be changed.

4. How Do I Maintain My Hydraulic System?

On a weekly and monthly basis, you should carry out a few routine tasks. Look out for the typical failure factors, such as filters, parts, and oil level and quality. The longevity of your system can be significantly increased with proper maintenance.