How to Bleed Brakes on F600 and F700 Ford Trucks and Other Medium-Duty Truck Applications

Medium-duty trucks like the classic Ford F600 are workhorses, but keeping them roadworthy requires proper brake maintenance. One of the most important (and sometimes frustrating) jobs is bleeding the brake system. Whether you’ve just replaced a master cylinder, installed a new Hydrovac unit, or opened up brake lines for service, air will enter the system. If it isn’t removed, your pedal will feel spongy, and braking power will be compromised.

This guide will walk you through how to bleed brakes on an F600 or similar medium-duty trucks. We’ll cover tools, methods, common issues, and practical tips so you can get firm, reliable brake pressure again.

If you need to replace your hydrovac, we carry these units. Feel free to call us at 828-242-3795 to identify the correct hydrovac booster for your specific truck. Please click on the links below for your specific application:

2510065 Hydrovac for Ford F600, Ford F700, and Ford F800 trucks

2508827 Hydrovac for Chevy C60 and Chevy C70 Trucks

2512076 Hydrovac For International 1600 through 1800 Medium Duty Trucks

We also carry hydrovac units, firewall units, master cylinders, wheel cylinders and brake shoes for all other medium duty trucks, school buses and motorhomes.

Why Brake Bleeding Matters

Brake systems rely on hydraulic pressure. When you press the pedal, brake fluid pushes against pistons inside the wheel cylinders or calipers. If air is in the lines, it compresses instead of transmitting force, resulting in a soft pedal or complete brake failure.

On older medium-duty trucks with long brake lines, large wheel cylinders, and Hydrovac boosters, air pockets are even harder to remove. A thorough bleeding process is essential before condemning parts as defective.

Tools and Supplies You’ll Need

• DOT 3 brake fluid (most older F-series trucks require this; always check your cap or manual).
• Bleeder wrench or appropriately sized line wrench.
• Clear vinyl hose to attach to bleeder screws.
• Catch bottle or container for expelled fluid.
• Vacuum bleeder (like a Mityvac pump) or pressure bleeder.
• Thread seal tape (optional, to prevent air being pulled in through loose threads).
• Shop rags, gloves, and eye protection.

Understanding the System

The F600 originally came with a Hydrovac brake booster and a single-circuit master cylinder. Many trucks today have been upgraded to dual-circuit systems for safety, but both setups require the same principle: air must be forced out starting from the farthest point and working toward the closest.

A check valve in the vacuum line protects the Hydrovac diaphragm from fuel vapors, and the so-called “proportioning valve” on these trucks is actually a safety switch that illuminates a warning light if one circuit loses pressure. Knowing these details helps you diagnose problems correctly.

Method 1: Manual Bleeding

The old-school way is to have one person pump the brake pedal while another opens and closes bleeder screws.

1. Fill the master cylinder reservoir.
2. With the engine off (no vacuum applied), open the Hydrovac bleeder screw #1.
3. Have a helper press the brake pedal firmly to the floor.
4. Close the bleeder before the pedal is released.
5. Repeat until no bubbles are seen in the clear hose.
6. Do the same for Hydrovac bleeder screw #2.
7. Move to the wheel cylinders, starting with the farthest (right rear), then left rear, right front, and finally left front.
8. Refill the reservoir often so air isn’t pulled back in.

This method works but can be slow and exhausting, especially on large systems.

Method 2: Vacuum Bleeding

A vacuum bleeder simplifies the job and avoids the need for a helper. Here’s how it works:

1. Fill the master cylinder to the correct level.
2. Attach the vacuum pump’s hose and clear line to the first bleeder screw.
3. Pump the vacuum to around 20–22 inHg before cracking the bleeder.
4. Watch as fluid (and bubbles) get pulled through the line.
5. Close the bleeder before releasing the vacuum.
6. Repeat until only solid fluid is coming out.
7. Keep topping off the master cylinder during the process.
8. Work in the same sequence: Hydrovac first, then wheel cylinders from farthest to nearest.

Pro tip: If you notice lots of bubbles despite multiple attempts, check the fittings. Air can sneak in through loose threads, making it appear as if there’s still air in the system. Applying a small amount of thread tape around the bleeder screw can stop this.

Method 3: Pressure Bleeding

Some mechanics prefer using a pressure bleeder that attaches directly to the master cylinder. This tool pushes fluid through the system at about 50 PSI, forcing air out at each bleeder without pumping the pedal or using vacuum.

Advantages:

• Consistent pressure and flow.
• Quicker on large-capacity systems.
• Less risk of introducing new air bubbles.

Drawback: Pressure bleeders can be expensive, but if you work on trucks regularly, they’re worth the investment.

Common Problems and Fixes

• No fluid movement: Check for leaks at the master cylinder or loose fittings. Air leaks prevent vacuum from pulling fluid.
• Endless bubbles: Often caused by loose bleeder screws or worn threads. Tighten securely or use thread tape.
• Pedal still soft after bleeding: Adjust the rear brakes. Slack adjusters or improperly set shoes can mimic air in the system.
• Fluid leaks during vacuum bleeding: Ensure the pump is designed for fluids. Air-only pumps will be ruined by brake fluid contamination.

Brake Fluid and Rust Concerns

DOT 3 is the standard for older trucks, but it has drawbacks: it absorbs moisture, corrodes steel lines, and strips paint. That’s why brake fluid turns dark over time. Regular fluid changes are recommended to extend the life of lines and wheel cylinders.

While hydraulic oil may seem tempting, it is not DOT-approved for road vehicles. Always use what’s specified on the cap or in the service manual.

Safety First

• Never crawl under a truck supported only by a jack. Use jack stands rated for your vehicle’s weight.
• Brake fluid is corrosive. Wipe up spills immediately and avoid contact with painted surfaces.
• After bleeding, test brake pressure before driving. Pedal should feel firm and not sink to the floor.

Final Thoughts

Bleeding brakes on F600, F700 or similar medium-duty truck takes patience, but it isn’t complicated. Whether you choose manual, vacuum, or pressure bleeding, the key is consistency: keep the master cylinder topped off, work in the correct sequence, and chase every last bubble of air out of the system.

If the pedal still feels spongy after careful bleeding, don’t assume the Hydrovac or master cylinder is defective. In many cases, the culprit is simply trapped air or misadjusted brakes. Take your time, check every connection, and you’ll restore safe, reliable stopping power to your truck.

Keeping these older trucks on the road is as much about knowledge as it is about parts. Once you’ve gone through the process, you’ll have the confidence to maintain your brakes without calling in outside help — and that’s a big win for any owner of a classic medium-duty rig.

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