1999-2003 Ford Windstar Brake Booster: Hissing Noises, Hard Pedal, and AdvanceTrac Explained

Symptoms of a Failing Power Brake Booster

A failing brake booster on a 1999-2003 Ford Windstar gives clear warning signs. Ignoring them is dangerous, as it can lead to a sudden and dramatic increase in the effort required to stop the van. The most common symptoms involve sounds you can hear and feelings through the brake pedal.

1. Hissing Sound When Pressing the Brake Pedal

This is the most definitive sign of a failed brake booster. You will hear a distinct hissing or 'whooshing' sound from under the dashboard near the brake pedal, but only when the pedal is being pressed. This sound is caused by a tear in the booster's internal rubber diaphragm, which creates a vacuum leak. If the hissing sound is constant even when the pedal is not pressed, the problem may be the booster's plunger seal or the vacuum supply hose.

2. Hard Brake Pedal

If the brake pedal suddenly becomes very difficult to push down, feeling stiff or hard like pressing against a wall, the power assist has likely failed. You are now trying to stop the vehicle using only your own leg strength, which is often insufficient for safe braking, especially in an emergency. This symptom is often accompanied by a longer stopping distance.

3. Engine Problems (Rough Idle or Stalling)

Because the booster operates on engine vacuum, a significant leak in the diaphragm can allow unmetered air into the intake manifold. This disrupts the engine's air-fuel mixture, which can cause a rough or stumbling idle, a drop in RPMs, or even cause the engine to stall completely when you apply the brakes. This vacuum leak can also be significant enough to trigger a Check Engine Light for a lean air-fuel mixture (like code P0171) or random misfires (P0300).

4. Brake Pedal Doesn't Behave Normally

A healthy booster will cause the brake pedal to drop slightly if you are holding it down when you start the engine. If the pedal doesn't move at all, or if it feels high and firm, the booster is not getting vacuum or is not working internally.

Known Issues, Recalls, and Technical Service Bulletins (TSBs)

Major Safety Recall: Risk of Fire (09S09)

While not a recall on the brake booster itself, all 1999-2003 Windstar owners must be aware of NHTSA Safety Recall 09S09. This recall addresses a faulty Speed Control Deactivation Switch (SCDS) mounted on the master cylinder. This switch can leak brake fluid, which can overheat and cause a fire in the engine compartment. On the Windstar specifically, the leaking fluid can also travel down the wiring harness to the ABS module, creating a fire risk there, even when the vehicle is turned off and parked. It is critical to ensure this recall work has been performed on any vehicle.

Other TSBs and Issues

• Brake Noise/Roughness: Ford issued several TSBs (e.g., 15372, 15933) for issues like brake roughness, pulsation, squealing, or rattling noises from the front brakes, which are typically related to brake pads and rotors, not the booster.
• AdvanceTrac Calibration: TSB 16919 notes that the AdvanceTrac stability system may not be recalibrated properly using the dealer tool (WDS), highlighting the complexity of this optional system.

Compatibility Warning: AdvanceTrac vs. Standard Brakes

This is the most important detail when purchasing a replacement brake booster for a 2002-2003 Ford Windstar. There are two different types of boosters that correspond to three different factory braking systems. Choosing the wrong one will result in improper brake function.

For model years 1999-2001, there was generally only one type of booster, which is the 'Standard Booster' that covers the later non-AdvanceTrac models. The confusion arises in 2002-2003, where AdvanceTrac was an option.

How to Tell if Your Windstar Has AdvanceTrac:

• Check the Dashboard: When you first turn the key to the 'ON' position, a 'Service AdvanceTrac' or similar indicator light should briefly illuminate on the instrument cluster if the system is installed.
• Look for a Button: Some vehicles with AdvanceTrac have a button on the center console or dashboard that allows you to turn the system off.
• Check Your VIN: A Ford dealership or a comprehensive VIN decoder can tell you the original options your vehicle was built with.

Step-by-Step Diagnosis

You can perform a simple, definitive test for booster failure in your driveway.

1. With the engine off, pump the brake pedal 5-6 times. This will exhaust any stored vacuum in the booster. The pedal should feel firm and hard.
2. Once the pedal is firm, press down on it with moderate, steady force.
3. While holding the pedal down, start the engine.
4. If the booster is working: As the engine starts and creates vacuum, you should feel the pedal sink downward an inch or two under your foot.
5. If the booster has failed: The pedal will not move or will remain hard to press. This confirms a lack of power assist.

Buying a Used Power Brake Booster

A used OEM brake booster can be a reliable and cost-effective replacement. Because failure is often due to the rubber diaphragm drying out over time, a part from a lower-mileage, newer-model-year vehicle is ideal, but visual inspection is most important.

• Inspect for Fluid Contamination: The number one killer of brake boosters is a leaking master cylinder. Look at the front of the booster where the master cylinder mounts. There should be no signs of brake fluid residue, paint peeling, or rust. If you see evidence of a leak, the booster's diaphragm is likely damaged.
• Check for Rust: Heavy rust on the canister body can compromise its integrity over time. Look for a part with clean paint and minimal surface corrosion.
• Verify Compatibility: Crucially, for 2002-2003 models, confirm if the donor vehicle had AdvanceTrac. Match the part to your vehicle's specific system.
• Check the Vacuum Port: Ensure the plastic vacuum check valve port on the booster is not cracked or broken.

Cost to Replace a 1999-2003 Ford Windstar Brake Booster

Replacing the brake booster is a moderately difficult job. While the work in the engine bay is straightforward, accessing the nuts and the pushrod clip under the dashboard can be very challenging.

Replacement Overview & Torque Specs

The replacement process involves unbolting the master cylinder from the booster, disconnecting the vacuum hose, and then, from inside the vehicle, unbolting the booster from the firewall and disconnecting the pushrod from the brake pedal.

Frequently Asked Questions (FAQ)