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The Ford F700, a popular medium-duty truck, was used in various industries during its production years, particularly for delivery, construction, and other heavy-duty work. A key component in ensuring the safety and performance of any truck is its braking system, and in the case of the 1986 F700, rear air brakes play an essential role. In this guide, we will explore the workings of rear air brakes on this model, common issues, maintenance tips, and troubleshooting techniques.
What Are Air Brakes and How Do They Work?
Air brakes, also known as pneumatic brakes, use compressed air to operate braking mechanisms in vehicles, particularly large trucks and buses. Unlike hydraulic brakes, which use fluid to generate force, air brakes rely on air pressure to engage the brake pads or shoes, which then press against the brake drums or rotors.
The system operates through several components:
Key Components of the Rear Air Brakes on a 1986 Ford F700
To understand the potential issues with rear air brakes on this vehicle, it’s essential to know the components involved:
While air brakes are designed to be reliable and durable, certain issues can occur over time, especially in older models like the 1986 F700. Some common problems with rear air brakes include:
1. Air Leaks
Air leaks are one of the most common issues in air brake systems. These leaks can occur at any point in the system, from the compressor to the brake chambers. If air is leaking, the brake system will lose pressure, leading to diminished braking performance or even brake failure.
Sluggish or delayed brake response can occur if the air pressure is not building up quickly enough or if there is an issue with the delivery of air to the rear brake chambers.
Over time, the brake shoes on the rear air brake system can wear down due to the friction and heat generated during braking. Worn brake shoes can lead to longer stopping distances and reduced braking power.
The spring brake is a critical safety feature, designed to engage automatically if the air pressure drops below a certain level. If this system malfunctions, it can leave the vehicle vulnerable to brake failure in the event of an air pressure loss.
Air brakes require periodic adjustment to ensure proper function. If slack adjusters are not calibrated correctly, the brakes may not engage properly or evenly, leading to uneven braking or unnecessary wear.
To properly diagnose issues with the rear air brakes on your 1986 Ford F700, here’s a step-by-step troubleshooting process:
1. Inspect for Air Leaks
Regular maintenance is key to keeping your rear air brakes functioning properly. Here are some preventive maintenance tips:
The rear air brake system on the 1986 Ford F700 is a critical component for the safety and performance of the vehicle. While these systems are robust and reliable, they are not immune to wear and tear. Understanding the common issues such as air leaks, sluggish brake response, worn brake shoes, and faulty spring brakes can help operators troubleshoot problems and maintain the braking system efficiently. Regular maintenance, including air pressure checks, brake inspections, and adjusting slack adjusters, will ensure that your truck’s air brakes continue to perform reliably for years to come.
What Are Air Brakes and How Do They Work?
Air brakes, also known as pneumatic brakes, use compressed air to operate braking mechanisms in vehicles, particularly large trucks and buses. Unlike hydraulic brakes, which use fluid to generate force, air brakes rely on air pressure to engage the brake pads or shoes, which then press against the brake drums or rotors.
The system operates through several components:
- Compressor: Compresses air and stores it in a reservoir tank.
- Air Reservoirs: Store the compressed air for later use.
- Brake Pedal: The operator applies force to the brake pedal, which activates the air valve.
- Brake Chambers: These are located near the wheels and use the air pressure to push the brake shoes or pads against the drum or rotor.
- Slack Adjusters: Adjust the position of the brake shoes to ensure proper braking force.
Key Components of the Rear Air Brakes on a 1986 Ford F700
To understand the potential issues with rear air brakes on this vehicle, it’s essential to know the components involved:
- Brake Chambers: Located at the rear axle, these chambers are responsible for applying pressure to the brake shoes when air is applied.
- Spring Brake Mechanism: This mechanism ensures that if the air pressure is lost, the brakes will engage automatically as a safety measure. The spring brake is an emergency feature that helps prevent runaway vehicles.
- Slack Adjusters: These devices automatically adjust the brake shoes to maintain the correct distance from the drum, ensuring optimal braking performance.
- Treadle Valve and Air Pedal: The driver uses the treadle valve, located near the brake pedal, to modulate air pressure to the rear brakes.
- Brake Shoes and Drums: These are the parts that actually make contact and slow down the vehicle. Over time, brake shoes and drums can wear out, requiring replacement.
While air brakes are designed to be reliable and durable, certain issues can occur over time, especially in older models like the 1986 F700. Some common problems with rear air brakes include:
1. Air Leaks
Air leaks are one of the most common issues in air brake systems. These leaks can occur at any point in the system, from the compressor to the brake chambers. If air is leaking, the brake system will lose pressure, leading to diminished braking performance or even brake failure.
- Symptoms: The brakes may feel weak, or the air pressure gauge may show a drop in pressure. You might also hear a hissing sound if there’s a noticeable air leak.
- Potential Causes: Leaking air hoses, cracked brake chambers, faulty seals, or damaged fittings.
Sluggish or delayed brake response can occur if the air pressure is not building up quickly enough or if there is an issue with the delivery of air to the rear brake chambers.
- Symptoms: The brakes take longer to engage or don’t feel as responsive as they should.
- Potential Causes: Low air pressure, malfunctioning air compressor, or dirty air filters restricting airflow.
Over time, the brake shoes on the rear air brake system can wear down due to the friction and heat generated during braking. Worn brake shoes can lead to longer stopping distances and reduced braking power.
- Symptoms: The vehicle may take longer to stop, or the brakes may make a grinding noise if the shoes are excessively worn.
- Potential Causes: Normal wear and tear, driving habits (e.g., frequent heavy braking), or improper adjustment of slack adjusters.
The spring brake is a critical safety feature, designed to engage automatically if the air pressure drops below a certain level. If this system malfunctions, it can leave the vehicle vulnerable to brake failure in the event of an air pressure loss.
- Symptoms: The spring brakes may not engage in an emergency, or the truck may not stop as expected in case of a pressure drop.
- Potential Causes: Faulty spring brake valves, air pressure loss, or internal damage to the spring mechanism.
Air brakes require periodic adjustment to ensure proper function. If slack adjusters are not calibrated correctly, the brakes may not engage properly or evenly, leading to uneven braking or unnecessary wear.
- Symptoms: Uneven braking, excessive pedal travel, or pulling to one side during braking.
- Potential Causes: Incorrect slack adjuster settings, worn-out components, or failure to adjust the system after maintenance.
To properly diagnose issues with the rear air brakes on your 1986 Ford F700, here’s a step-by-step troubleshooting process:
1. Inspect for Air Leaks
- Check hoses and fittings: Inspect all air hoses, fittings, and connections for signs of wear, cracks, or leaks.
- Test with soap solution: Spray a soap solution on connections to look for bubbles, indicating a leak.
- Check brake chambers: Inspect the brake chambers for damage or leaks. If necessary, replace them.
- Gauge Check: Ensure the air pressure gauge shows the correct pressure range (typically 90-120 psi for most systems). If the pressure is low, check the air compressor and air tanks for issues.
- System Test: Start the engine and apply the brakes. If the pressure is not building up quickly enough, the compressor or governor may need attention.
- Visual Inspection: Check the thickness of the brake shoes. If they’re worn down below the minimum thickness (usually around 1/4 inch), replace them.
- Check for Wear Patterns: Uneven wear can indicate issues with brake adjustment, slack adjusters, or misalignment.
- Engage and Disengage: Test the spring brake by applying the brakes and turning off the engine. The spring brake should engage when air pressure is lost.
- Check for Air Loss: Ensure the spring brake system holds pressure and engages when necessary. Replace the spring brake valve if it’s not functioning properly.
- Manual Adjustment: If the brake shoes are not positioned properly, adjust the slack adjusters according to the manufacturer’s specifications. Ensure there’s no excessive play in the brake mechanism.
- Automatic Adjustment: Check whether the slack adjusters are working correctly. If not, they may need to be replaced or serviced.
Regular maintenance is key to keeping your rear air brakes functioning properly. Here are some preventive maintenance tips:
- Change air filters regularly to ensure clean air supply to the brake system.
- Check air reservoirs for moisture: Drain the air tanks periodically to remove accumulated moisture, which can freeze and cause blockages in cold weather.
- Inspect brake components: Regularly check brake shoes, drums, and springs for signs of wear or damage.
- Test brake function: Perform regular brake tests, ensuring they engage smoothly and with adequate pressure.
- Service the air compressor: Make sure the air compressor is functioning properly and maintaining the correct pressure.
The rear air brake system on the 1986 Ford F700 is a critical component for the safety and performance of the vehicle. While these systems are robust and reliable, they are not immune to wear and tear. Understanding the common issues such as air leaks, sluggish brake response, worn brake shoes, and faulty spring brakes can help operators troubleshoot problems and maintain the braking system efficiently. Regular maintenance, including air pressure checks, brake inspections, and adjusting slack adjusters, will ensure that your truck’s air brakes continue to perform reliably for years to come.
