Water in the Hystat: Troubleshooting and Solutions for the 953C Bobcat

[MikePhua]

Heavy equipment like the Bobcat 953C uses hydraulic systems to provide power for a variety of operations. The hydraulic system, particularly the hydraulic static transmission (Hystat) system, is a crucial component in driving the machine’s tracks and lifting mechanisms. When water gets into the hydraulic system, it can cause significant problems, affecting the efficiency and longevity of the equipment. This article will explore the causes of water contamination in the Hystat system of a Bobcat 953C, its potential consequences, and the steps to mitigate such issues.
Understanding the Hystat System in the Bobcat 953C
The Bobcat 953C is a compact track loader equipped with a hydraulic static transmission (Hystat) system, which is designed to provide smooth, stepless control of forward and reverse motion. The Hystat system operates by using hydraulic fluid to transfer power to the tracks. This system provides the benefits of infinitely variable speed control, making it ideal for heavy lifting and high-traction applications. The hydraulic fluid also serves to cool and lubricate various components within the system.
However, when water enters the hydraulic system, it can compromise the fluid’s ability to properly lubricate and cool the system, leading to decreased performance and potential mechanical failures.
Causes of Water Contamination in the Hydraulic System
Water can enter the hydraulic system of a Bobcat 953C in several ways, including the following:
1. Condensation
Hydraulic systems operate under pressure and temperature fluctuations, which can cause condensation to form inside the components. This is especially true in colder climates where the machine is exposed to extreme temperature changes. The moisture in the air can condense into water droplets inside the hydraulic tank and hoses, leading to water contamination over time.
2. Faulty Seals or Gaskets
The hydraulic system relies on seals and gaskets to keep the hydraulic fluid contained and free from contaminants. Over time, seals can deteriorate or become damaged due to wear, improper maintenance, or environmental factors. Once a seal fails, water can enter the system through the damaged area, causing the hydraulic fluid to become contaminated.
3. Water from the External Environment
In certain situations, such as working in wet conditions or during rain, water can enter the hydraulic system through vents, breather caps, or other openings. Additionally, if the equipment operates in areas with high humidity or where the machine frequently comes into contact with water, it can increase the likelihood of water ingress into the system.
4. Contaminated Hydraulic Oil
Another possible cause is the introduction of contaminated hydraulic oil. If the hydraulic oil is stored in environments where moisture is present or if it comes into contact with water during refilling, the system may be contaminated from the very start.
Effects of Water Contamination in the Hydraulic System
Water contamination in the hydraulic system of the Bobcat 953C can lead to several issues that affect the machine’s performance and longevity. These include:
1. Reduced Lubrication Efficiency
Water mixed with hydraulic fluid decreases the fluid’s ability to lubricate internal components effectively. As a result, components like pistons, pumps, and motors may experience increased friction and wear, leading to a higher likelihood of mechanical failure.
2. Corrosion
Water in the hydraulic system can cause metal parts to rust and corrode. Corrosion can degrade critical components such as hydraulic valves, cylinders, and hoses, leading to leaks, reduced system efficiency, and costly repairs.
3. Decreased Performance
When water mixes with hydraulic fluid, the fluid’s viscosity is reduced, which in turn can lead to poor hydraulic performance. You may notice sluggish movement, jerky motions, or failure to respond properly to control inputs. This can make the loader harder to operate, and in extreme cases, the system could fail entirely.
4. Contamination of Filters
Water in the hydraulic system can clog the filters, which are designed to remove contaminants from the fluid. When the filters become clogged, they can no longer perform their function, leading to increased levels of dirt and debris within the hydraulic fluid. This can result in further damage to the system and increase the risk of failure.
Steps to Diagnose and Resolve Water Contamination
Identifying water contamination in the hydraulic system of a Bobcat 953C early can help mitigate the damage and prevent further issues. Here are some steps you can take to diagnose and resolve the problem:
1. Visual Inspection of the Hydraulic Fluid
One of the first steps in diagnosing water contamination is inspecting the hydraulic fluid. Clean hydraulic fluid is usually clear or slightly amber, but if it looks milky or has a cloudy appearance, it likely contains water. Milky fluid can also lead to poor performance, so it’s crucial to check for this sign regularly.
2. Check the Hydraulic Fluid Levels
Low hydraulic fluid levels can indicate a leak in the system, which may be allowing water to enter. Be sure to check the fluid level regularly and top up the system with clean hydraulic fluid as necessary. If the fluid level drops unexpectedly, this could be a sign of a more serious leak or water ingress.
3. Inspect Seals, Gaskets, and Components
Inspect the seals and gaskets around the hydraulic lines, tank, and other components for any signs of wear or damage. If you find any faulty seals or gaskets, replace them immediately to prevent further water entry. Look for cracks, tears, or visible gaps that could allow water to infiltrate the system.
4. Drain and Flush the Hydraulic System
If you suspect water contamination in the hydraulic system, the best course of action is to drain the system and flush it thoroughly. This will remove the contaminated hydraulic fluid and water. After draining, refill the system with fresh hydraulic fluid and ensure that the fluid level is correct.
5. Replace the Filters
Once the system has been flushed, replace the filters to remove any dirt or debris that may have accumulated. Clean filters are essential for maintaining the hydraulic fluid’s cleanliness and preventing further damage to the system.
6. Prevent Future Water Ingress
To prevent water contamination from happening in the future, regularly inspect the breather caps and vents for any signs of wear or clogging. In addition, store the equipment in dry, well-ventilated areas, and avoid operating the machine in extremely wet or humid conditions whenever possible.
Preventative Maintenance Tips
Preventing water contamination is much easier than dealing with the damage it causes. Regular maintenance is key to protecting the hydraulic system of your Bobcat 953C.

• Check Hydraulic Fluid Regularly: Make it a habit to check the fluid’s condition and levels frequently. Look for any changes in appearance that could signal contamination.
  
• Inspect Seals and Gaskets: Routinely check the integrity of seals and gaskets, and replace them at the first sign of wear or degradation.
  
• Store Equipment Properly: Ensure that your Bobcat 953C is stored in a dry, well-ventilated environment to reduce the risk of water ingress.
  
• Service the Cooling System: Ensure that the cooling system is functioning properly to help keep temperatures stable and prevent condensation from forming within the system.
  

Conclusion
Water contamination in the hydraulic system of the Bobcat 953C is a serious issue that can lead to reduced performance, increased wear and tear, and potentially costly repairs. By understanding the causes and effects of water in the hydraulic system and taking proactive measures, you can maintain the integrity of the machine’s Hystat system and extend its service life. Regular inspections, timely maintenance, and using proper storage techniques are essential to avoiding this common issue.