How to Plumb In 3rd SCV on John Deere 4520: Easy Guide

Are you frustrated by the limitations of your two-spool hydraulic system when trying to operate complex attachments like angle blades or grapples? Many John Deere 4520 owners face this exact bottleneck, limiting their productivity and requiring manual intervention that wastes valuable time. If you are looking for a reliable solution, learning how to plumb in 3rd SCV on John Deere 4520 is the most cost-effective upgrade you can make. This guide will walk you through the process safely, ensuring you gain full control over your third hydraulic function without compromising your tractor’s warranty or performance.

Why Add a Third SCV to Your John Deere 4520?

Before diving into the wrenches and hoses, it is essential to understand why this modification is so popular among compact utility tractor owners. The John Deere 4520 is a robust machine, but its standard configuration often comes with only two rear remote valves (SCVs).

The Limitation of Two Spools

With only two spools, you are typically forced to choose between:

1. Running a top-and-tilt kit.
2. Operating a hydraulic angle blade.
3. Using a grapple bucket.

If you want to use a grapple and an angle blade, you must constantly disconnect and reconnect hydraulic lines. This is not only tedious but also introduces dirt and debris into the hydraulic couplers, which can lead to premature wear.

The Benefit of the Third Function

By adding a third Selective Control Valve (SCV), you unlock simultaneous operation. You can keep your loader hooked up permanently while still having independent control over auxiliary attachments. According to industry data, farmers who utilize full hydraulic controls reduce attachment setup time by up to 40%, significantly increasing daily efficiency.

Understanding the John Deere 4520 Hydraulic System

To successfully plumb in a third valve, you must understand where the hydraulic power originates. The 4520 uses a load-sensing hydraulic system. This means the pump only produces flow when there is a demand, which improves fuel efficiency but requires precise plumbing.

Key Components Involved

• The Hydraulic Pump: Located at the front of the engine, it supplies pressurized oil.
• The Priority Valve: Ensures steering gets priority over other functions.
• The Existing SCVs: Usually located under the seat or behind the operator’s station.
• The Power Beyond Port: This is the critical connection point for adding additional valves.

Expert Tip: Always consult your specific operator’s manual for hydraulic diagrams. While most 4520s share similar architectures, production year variations can exist. For general hydraulic principles, you can refer to Wikipedia’s article on Hydraulic Machinery to understand the basic physics of fluid power.

Tools and Parts Required

Gathering the right materials before starting is crucial. A trip back to the hardware store mid-job can lead to contamination risks if lines are left open.

Essential Parts List

Tools Needed

• Socket set (Metric and SAE)
• Line wrenches (to prevent rounding nuts)
• Drain pan
• Clean rags (lint-free)
• Thread sealant (hydraulic rated)

Step-by-Step: How to Plumb In 3rd SCV on John Deere 4520

Follow these steps meticulously. Safety is paramount when working with high-pressure hydraulic systems.

Step 1: Preparation and Safety

Park the tractor on a level surface. Lower all implements to the ground to relieve hydraulic pressure. Turn off the engine and engage the parking brake. Wait at least 15 minutes for the hydraulic oil to cool down and settle. Hot oil can cause severe burns and expands, leading to inaccurate fluid level readings.

Step 2: Locate the Power Beyond Port

On the John Deere 4520, the easiest way to add a third valve is to tap into the “Power Beyond” circuit of the existing second valve or the main hydraulic block.

1. Remove the side panels near the operator’s station.
2. Identify the existing SCV block.
3. Look for the port labeled “PB” or “Power Beyond.” If your current setup does not have a dedicated PB port, you may need to install a divider block or replace the existing valve stack with a three-spool unit.

Step 3: Install the New Valve Body

1. Mount the new SCV valve body using the provided bracket. Secure it tightly to prevent vibration damage.
2. Ensure the lever mechanism is accessible from the driver’s seat. You may need to extend the linkage rod if the valve is mounted remotely.

Step 4: Connect the Pressure Line

1. Connect a high-pressure hose from the Pressure Inlet (P) of the new valve to the Power Beyond port of the previous valve or the main supply line.
2. Use thread sealant sparingly on the fittings. Do not let sealant enter the hydraulic lines, as it can clog filters.
3. Tighten the fittings using a line wrench to avoid stripping the nuts. Torque to manufacturer specifications (typically 25–30 ft-lbs for 1/2″ lines).

Step 5: Connect the Return Line

1. Connect the Tank Port (T) of the new valve directly to the hydraulic reservoir return line.
2. Critical: Do not connect the return line to a pressurized line. It must go straight to the tank or filter housing inlet.
3. Ensure the return hose has no kinks, as restricted return flow can blow out seals.

Step 6: Install Couplers and Hoses

1. Attach the agricultural couplers to the Work Ports (A and B) of the new valve.
2. Route the hoses along the tractor frame, securing them with zip ties or clamps every 12 inches to prevent rubbing against moving parts.

Step 7: Bleeding the System

Air in the hydraulic system causes spongy controls and potential damage.

1. Check the hydraulic fluid level. Add oil if necessary.
2. Start the engine and let it idle.
3. Slowly cycle the new SCV lever back and forth 10–15 times. You may hear a whining noise; this is normal as air escapes.
4. Check for leaks at all connections. Tighten if necessary.
5. Re-check the fluid level after the system has warmed up.

Common Mistakes to Avoid

Even experienced DIYers can stumble during this process. Here are the most frequent errors:

• Ignoring Filtration: Adding new lines introduces contaminants. Always change the hydraulic filter after completing the installation.
• Using Incorrect Hose Ratings: Standard automotive hoses cannot withstand the 3,000+ PSI pressure of tractor hydraulics. Always use certified hydraulic hoses.
• Over-tightening Fittings: JIC fittings seal on metal-to-metal contact. Over-tightening can crack the flare, causing immediate leaks. Snug is sufficient.

FAQ Section

1. Will adding a 3rd SCV void my John Deere warranty?

Modifications that do not cause damage to the original equipment generally do not void the entire warranty. However, if a hydraulic failure occurs and it is traced back to improper installation of the third valve, John Deere may deny coverage for that specific repair. Always keep records of your work and use high-quality parts.

2. Can I do this without replacing the existing valves?

Yes. Most kits are designed to add onto the existing system using the Power Beyond port. However, if your tractor only has one remote, you might need to replace the single-spool valve with a multi-spool stack. For the 4520, which usually comes with two, adding a third is typically an additive process.

3. What size hydraulic hoses do I need for a John Deere 4520?

Most John Deere compact utilities use 1/2-inch or 9/16-18 JIC fittings for rear remotes. However, you should measure your existing couplers or consult your parts manual. Using the wrong size will result in leaks or restricted flow.

4. How much does it cost to plumb in a 3rd SCV?

A DIY approach typically costs between $300 and $600 for parts (valve, hoses, couplers, brackets). Having a dealer perform the installation can cost upwards of $1,200 due to labor rates. Doing it yourself saves significant money.

5. Do I need to adjust the relief valve?

In most cases, no. The main system relief valve protects the entire circuit. However, if you notice the new function is sluggish compared to the others, check if the new valve has its own internal relief setting and adjust it to match the system pressure (usually around 2,500–3,000 PSI).

Conclusion

Learning how to plumb in 3rd SCV on John Deere 4520 is a transformative upgrade for any owner looking to maximize their tractor’s potential. By following this guide, you can achieve professional-grade results, saving hundreds of dollars in labor costs while gaining the flexibility to run multiple attachments seamlessly.

Remember, patience and cleanliness are your best tools when working with hydraulics. Take your time, double-check your connections, and enjoy the newfound versatility of your machine.

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