John Deere 35G Hydraulic Pump Troubleshooting and Replacement Guide

Introduction

This comprehensive guide is designed for John Deere 35G excavator owners, operators, and technicians who are seeking to troubleshoot, maintain, or replace the John Deere 35G hydraulic pump and related hydraulic system components. Here, you’ll find step-by-step troubleshooting instructions, essential maintenance tips, and a curated list of replacement parts—including both OEM and aftermarket options. Maintaining the health of your John Deere 35G hydraulic pump is crucial for ensuring optimal machine performance, preventing costly downtime, and extending the life of your equipment.

 

Why Hydraulic Pump Health Matters

The hydraulic pump is the heart of your John Deere 35G excavator’s hydraulic system, responsible for generating the pressure and flow needed to power all major functions, from digging to travel. Common hydraulic pump issues include low hydraulic pressure, slow operation, noise, and overheating, often caused by contamination or clogged filters. Addressing these problems promptly is essential to avoid further damage and maintain productivity. The John Deere 35G hydraulic pump is specifically designed for this model, with a product number of FYD00012773. The hydraulic system operates at a system pressure typically rated at 3,550 psi (24,500 kPa), and the total hydraulic flow capacity is approximately 23.5 gpm (89 L/min) combined. The weight of the hydraulic pump for the John Deere 35G excavator is approximately 41.086 pounds, with dimensions of 6.9 inches in height, 7 inches in width, and 12 inches in length.

 

If you’re experiencing issues with your John Deere 35G hydraulic pump, this guide will help you identify the root cause and provide actionable solutions. If these steps do not resolve the issue, proceed to the next troubleshooting section for further guidance.

 

No Hydraulic Functions

Please ensure that the pilot shutoff lever is in the unlocked (DOWN) position. This is crucial for proper functioning.

 

To obtain an accurate oil level reading, it is essential to park the machine on a level surface. Make sure the arm cylinder is fully retracted and the bucket cylinder is fully extended. Lower the bucket and blade to the ground, and then stop the engine. By doing so, you can check the oil level, which should be between the top and bottom marks on the sight gauge located on the hydraulic tank.

 

Additionally, it is important to check the PILOT SHUT OFF 5 amp fuse (F17) and replace it if necessary, as electrical issues in the starting and control circuits are covered in more depth in our John Deere 35G electrical system repair guide.

 

Another crucial step is to inspect and clean the suction screen, which is located within the hydraulic tank. Regular maintenance of the suction filter is necessary to ensure optimal performance.

 

Recommended Hydraulic Fluid: 

John Deere HY-GARD™ or an equivalent fluid meeting J20C specifications is recommended as hydraulic fluid.

 

System Pressure:

The hydraulic system operates at a system pressure typically rated at 3,550 psi (24,500 kPa).

 

Hydraulic Flow Capacity:

The total hydraulic flow capacity of the John Deere 35G excavator is approximately 23.5 gpm (89 L/min) combined.

 

If these steps do not resolve the issue, proceed to check for slow or weak hydraulic functions in the next section.

Hydraulic Functions Are Slow or Have Little Or No Power

As mentioned before, it is essential to check the oil level and inspect the suction filter. Common hydraulic pump issues include low hydraulic pressure, slow operation, noise, and overheating, often caused by contamination or clogged filters.

 

Recommended Hydraulic Fluid: 

John Deere HY-GARD™ or an equivalent fluid meeting J20C specifications is recommended as hydraulic fluid.

 

Hydraulic Warm-Up Procedure

When working in freezing weather conditions, it is recommended to perform a hydraulic warm-up. However, it is crucial to exercise caution to prevent injury from unexpected machine movement. Clear the area of all persons before running the machine through the warm-up procedure. If the machine is located inside a building, warm the travel circuit first and then move the machine to a clear area outside. It is important to note that cold oil can cause machine functions to respond slowly.

 

To perform the hydraulic warm-up, follow these steps:

1. Run the engine at 1/2 speed for 5 minutes. Avoid running the engine at fast or slow idle.
2. Initially, operate the travel and swing functions slowly, moving only short distances.
3. Operate the boom, arm, and bucket functions by moving the cylinders a short distance in each direction.
4. Continue cycling the cylinders by extending them until you reach the entire stroke. However, it is crucial to remember that holding the function actuated for more than 30 seconds can cause damage from hot spots in the control valve.
5. Actuate the bucket curl function (cylinder extend) for 10 seconds and then release for 5 seconds. Repeat this maneuver for 2-1/2 minutes.
6. Repeat the above procedure with the bucket dump function.
7. Operate all hydraulic functions to distribute warm oil in all cylinders, motors, and lines.
8. If hydraulic functions still move slowly, repeat steps 5 and 6.

Engine Speed Considerations

The engine’s speed directly influences the hydraulic pump's operation, affecting the efficiency and smoothness of machine functions. If the engine is operated too slowly, it can affect the speed and efficiency of hydraulic functions since the engine drives the hydraulic pump. Therefore, try increasing the engine’s speed if necessary, and be aware that modern machines often use an electronic throttle motor to control engine speed.

 

If you notice symptoms of sluggish performance, such as slow operation of the machine during digging or travel and the need for higher RPMs to maintain normal tasks, check the oil level and ensure the suction filter is clean, as these factors can significantly affect performance.

 

Checking Hydraulic Tank Cover

Lastly, it is crucial to check if the hydraulic tank cover needs replacement. A damaged cap can cause pressure loss, resulting in reduced performance and slower operations.

 

If these steps do not resolve the issue, proceed to the next section on hydraulic oil overheating.

 

Hydraulic Oil Overheats

If you notice that your hydraulic oil is overheating, it is important to identify the potential causes and take appropriate action, since excessive temperatures can also be a symptom of broader oil cooler performance problems.

 

Troubleshooting Checklist for Overheating

• Check for clogged filters: Clogged filters can restrict the flow of oil, leading to increased heat buildup. Inspect your filters and clean or replace them if necessary.
• Verify the oil level: Low oil levels can also contribute to overheating. Check the oil level in your hydraulic system and top it up if needed.
• Ensure correct oil viscosity: Using the correct oil viscosity is essential for maintaining the proper functioning of your hydraulic system. Refer to the manufacturer's guidelines or consult your authorized dealer.
• Inspect and clean the radiator: The radiator plays a crucial role in dissipating heat from the coolant. Inspect for any dirt, debris, or blockages and clean thoroughly if necessary.
• Straighten bent fins: Bent fins on the radiator can disrupt airflow, reducing its effectiveness in cooling the hydraulic oil. Straighten any bent fins to restore proper airflow.
• Consider oil contamination: Contaminated oil can also contribute to overheating. If you suspect oil contamination, seek assistance from your authorized dealer.

 

Recommended Hydraulic Fluid:
John Deere HY-GARD™ or an equivalent fluid meeting J20C specifications is recommended as hydraulic fluid.

 

If overheating persists after these checks, continue to the next section on oil foaming issues.

 

Oil Foams

If you encounter issues with oil foaming in your hydraulic system, it is crucial to address the problem promptly.

 

Troubleshooting Checklist for Oil Foaming

• High or low oil level: Improper oil levels, whether too high or too low, can lead to foaming. Ensure that the oil level is within the recommended range.
• Incorrect oil type: Using the wrong type of oil can also result in foaming. Verify that you are using the correct oil specified by the manufacturer.
• Water or air in the oil: Presence of water or air in the hydraulic oil can cause foaming. Check for any signs of water contamination or air entrainment in the oil.
• Inspect oil lines: Check for any kinks or dents in the oil lines that could disrupt oil flow and contribute to foaming.

 

If you suspect oil contamination or encounter persistent issues with foaming, it is always advisable to seek guidance from your authorized dealer.

 

If foaming is not the issue, proceed to the next troubleshooting section for swing and travel problems.

 

No Swing Function

• Ensure that the pilot shutoff lever is in the unlocked (down) position.
• Thoroughly inspect and correct any pinched or kinked pilot control valve hoses to ensure smooth operation and functionality.

 

If swing function is restored, continue to monitor for travel speed issues below.

 

Slow Travel Speed Only

The pilot control valve is responsible for regulating the flow of hydraulic fluid to the excavator’s travel motors or tracks. When troubleshooting slow travel speed, it is essential to inspect both the pilot control valve and its hoses for any pinched or kinked areas, as this ensures proper hydraulic flow to the excavator's travel motors and maintains operational efficiency. Addressing this issue will help restore the normal travel speed of the equipment.

 

If travel speed remains slow, check for jerky travel as described in the next section.

 

Travel is Jerky

• One possible solution to jerky travel movements is to increase the engine's speed. The engine and the hydraulic system are interconnected, and slow engine speeds can lead to stalling of the hydraulic system, especially when the equipment is under heavy load. Stalling can result in sudden stops and jerky movements as the hydraulic components struggle to function at reduced power levels.
• Additionally, it is recommended to check for any rocks or mud that may be jammed in the track frame. Clearing any obstructions will contribute to smoother and more consistent travel.

 

If jerky travel persists, proceed to the next section regarding engine stalling.

 

Engine Stops When Travel Or Control Lever Actuated

If the engine stops when you engage the travel or control lever, there are two potential causes:

1. Clogged fuel and air filters: It is advisable to replace these filters to ensure proper fuel flow and prevent any air blockages that may interfere with the engine's operation.
2. Air in the fuel system: Bleeding the air from the fuel system can resolve this issue. Follow the manufacturer's instructions or consult a professional for the correct procedure.

 

If the engine continues to stall, check the angle blade system as described below.

 

Angle Blade Suddenly Drift

• If the angle blade moves without your input, it indicates a potential problem with the system or circuit relief valves. It is crucial to check and replace these valves accordingly to restore proper functionality and prevent any unintended movements of the angle blade.

 

If the angle blade is not working or moves slowly, see the next section.

 

Angle Blade Doesn't Work or Moves Slowly

When experiencing a lack of movement or slow operation on one side of the blade, it is recommended to perform the following troubleshooting steps:

1. Check the hose routing for any leaks that may be affecting the hydraulic fluid flow. Repair any leaks or replace the hoses if necessary.
2. Inspect the center joint and ensure it is properly lubricated with grease. If there are any issues or signs of wear, address them accordingly, either through repair or replacement, to restore optimal performance.