Hydraulic Clutch Bleeding on the 1974 Dodge CNT900: A Step-by-Step Guide

[MikePhua]

Introduction: The Importance of Proper Hydraulic Clutch Maintenance
The hydraulic clutch system in older vehicles like the 1974 Dodge CNT900 is an essential component for smooth operation. Hydraulic clutch systems are widely used in trucks, especially in models designed for heavy-duty use, like the Dodge CNT900. These systems rely on hydraulic pressure to engage and disengage the clutch, ensuring that the vehicle shifts gears with minimal effort from the driver.
However, over time, these hydraulic systems can experience problems such as air entering the hydraulic lines, causing issues with clutch operation. This issue can lead to difficulty in engaging or disengaging gears, poor pedal feel, or even a complete failure to operate the clutch. One of the most effective ways to resolve these issues is by bleeding the hydraulic clutch system to remove trapped air.
This article will explain the process of bleeding the hydraulic clutch in the 1974 Dodge CNT900 and why it’s crucial for maintaining optimal performance.
What is Hydraulic Clutch Bleeding?
Hydraulic clutch bleeding is the process of removing air from the hydraulic clutch system. Air trapped in the hydraulic lines prevents the system from building proper pressure, which can result in poor clutch engagement or disengagement. The bleeding process allows fresh hydraulic fluid to flow into the system, displacing the air and ensuring that the clutch operates smoothly.
Signs You Need to Bleed the Hydraulic Clutch

1. Spongy or Soft Pedal Feel:
   One of the most common signs of air in the hydraulic clutch system is a soft or spongy pedal. If the clutch pedal feels less responsive than usual and doesn’t return to its normal position after being pressed, it may be due to air in the system.
   
2. Difficulty Shifting Gears:
   If the clutch fails to disengage fully when the pedal is pressed, it can cause difficulty when shifting gears, particularly when trying to shift into first or reverse. This is a common symptom of a hydraulic clutch that requires bleeding.
   
3. Unusual Noises:
   You may also hear unusual noises from the clutch area if air is trapped in the hydraulic lines. These sounds typically occur when trying to engage or disengage the clutch.
   
4. Low Fluid Level:
   If the hydraulic fluid level is low, it can lead to air entering the system, causing the clutch to lose its ability to function properly. Checking the fluid level regularly and ensuring there are no leaks in the system can help prevent this issue.
   

How to Bleed the Hydraulic Clutch on a 1974 Dodge CNT900

1. Prepare the Necessary Tools and Materials:
   Before you begin, gather the following tools and materials:
   • A wrench (typically 9/16” or 1/2” depending on the slave cylinder fitting)
     
   • A clear plastic hose
     
   • A catch container for old fluid
     
   • Brake or hydraulic fluid (ensure the correct type for your vehicle)
     
   • A helper (to press the clutch pedal while you open and close the bleed valve)
     
2. Locate the Bleed Valve on the Slave Cylinder:
   On the 1974 Dodge CNT900, the slave cylinder is usually located on the bellhousing near the transmission. The bleed valve is located on the slave cylinder and will typically have a small rubber cap over it. Remove the cap to expose the valve.
   
3. Attach the Plastic Hose to the Bleed Valve:
   Fit the clear plastic hose over the bleed valve to ensure that any fluid expelled during the bleeding process is directed into the catch container. Make sure the other end of the hose is submerged in the fluid catch container to prevent air from being drawn back into the system.
   
4. Check and Top-Up Fluid Levels:
   Before starting the bleeding process, check the hydraulic fluid reservoir. If the fluid level is low, top it up with the correct type of brake or hydraulic fluid. The fluid reservoir is usually located near the driver’s side of the vehicle, often under the hood.
   
5. Bleeding the System:
   Here’s the basic process:
   • Have a helper sit in the driver’s seat and press the clutch pedal all the way to the floor.
     
   • While the pedal is pressed down, use the wrench to open the bleed valve on the slave cylinder. You should see fluid and possibly some air bubbles in the clear plastic hose.
     
   • Close the valve before your helper releases the clutch pedal. This prevents air from being drawn back into the system.
     
   • Have the helper press the clutch pedal again, and repeat the process of opening and closing the valve until no more air bubbles appear in the fluid coming out of the hose. This may take several cycles, depending on how much air is trapped in the system.
     
6. Check Fluid Levels Again:
   Throughout the bleeding process, periodically check the fluid level in the reservoir. Ensure it does not drop too low, as this can introduce more air into the system. Top up the fluid as needed.
   
7. Test the Clutch Pedal:
   After you’ve completed the bleeding process, test the clutch pedal by pressing it. The pedal should feel firm, and you should notice improved clutch engagement. If the pedal still feels spongy or soft, you may need to repeat the bleeding process.
   
8. Check for Leaks:
   After bleeding the system, inspect the hydraulic lines, master cylinder, and slave cylinder for any signs of leaks. Leaks can lead to a loss of fluid, which can cause the clutch system to fail again.
   

Why Bleeding the Hydraulic Clutch is Essential for Performance
Over time, air can infiltrate the hydraulic clutch system, especially if there are any leaks in the lines or if the fluid level is low. Air in the system creates pressure imbalances, which affect the clutch’s ability to engage and disengage the gears properly. Bleeding the system restores hydraulic pressure, allowing for smooth operation and preventing potential damage to the clutch components.
Maintaining a properly functioning clutch system is crucial, especially in vehicles like the 1974 Dodge CNT900, which are often used for demanding tasks. A malfunctioning clutch can make it difficult to control the vehicle, leading to unsafe driving conditions and increased wear on the transmission.
Common Issues to Look Out For After Clutch Bleeding

• Air Bubbles: Sometimes, even after bleeding the system, small air bubbles may still remain. It’s important to keep an eye on the clutch pedal feel and performance after a bleed and be prepared to repeat the process if necessary.
  
• Clutch Master or Slave Cylinder Failure: If bleeding doesn’t resolve the issue, it could be a sign that the master or slave cylinder is failing and may need to be replaced. Both of these components are vital for hydraulic clutch operation and should be inspected if the problem persists.
  

Conclusion: Ensuring Smooth Operation of Your 1974 Dodge CNT900
Bleeding the hydraulic clutch in your 1974 Dodge CNT900 is a straightforward process that can significantly improve the clutch’s performance and overall driving experience. By following the steps outlined above, you can resolve clutch-related issues caused by trapped air in the hydraulic system and ensure that your truck operates at its best. Regular maintenance, including checking fluid levels and addressing any leaks, will also help extend the lifespan of your clutch system and prevent further issues down the road.
If problems persist after bleeding, don’t hesitate to consult a professional mechanic to inspect the hydraulic system for more complex issues, such as failing cylinders or damaged seals.