1. The Most Likely Culprit: Warped Rotors
* Symptoms: Pulsating brake pedal, especially noticeable at higher speeds. The pulsation often corresponds with the speed of the vehicle.
* Diagnosis: Visually inspect the rotors. Look for scoring, grooves, or obvious warping. A machinist's dial indicator can provide a precise measurement of rotor runout (warping).
* Fix: The most common solution is to resurface the rotors (if the thickness allows) or replace them. Resurfacing removes a small amount of material to eliminate the warp. However, if the rotors are too thin after resurfacing (check your owner's manual or a parts store for minimum thickness), they must be replaced. Replacing rotors is generally recommended over resurfacing, especially if they show significant wear or damage. Always replace rotors in pairs (front or rear).
2. Other Potential Causes:
* Brake Pads: Worn or unevenly worn brake pads can contribute to pulsating brakes. Inspect the pads for wear and thickness. Replace if necessary.
* Caliper Issues: A sticking or seized caliper can cause uneven brake pad wear and lead to pulsation. Check for smooth caliper movement and proper piston retraction. A seized caliper may need to be rebuilt or replaced.
* Wheel Bearings: Damaged wheel bearings can introduce vibrations that are felt in the brake pedal. Inspect the wheel bearings for play or noise. Replace if necessary.
* ABS Sensor/System: A faulty ABS sensor or a problem within the ABS system itself can sometimes manifest as pulsating brakes. This is less common but possible. Diagnosis requires a scan tool capable of reading ABS codes.
* Tires: While less likely, severely unbalanced or cupped tires can transmit vibrations to the steering wheel and brake pedal. Check tire condition and balance.
Troubleshooting Steps:
1. Visual Inspection: Begin by visually inspecting the brake system. Check the brake pads, rotors, calipers, and wheel bearings for any obvious problems.
2. Test Drive: Pay close attention to when the pulsation occurs. Does it happen only during braking at higher speeds? This points towards warped rotors.
3. Professional Diagnosis: If you're not comfortable performing these checks yourself, take your Expedition to a qualified mechanic. They have the tools and expertise to diagnose the problem accurately. A scan tool is beneficial to rule out ABS system issues.
Important Notes:
* Safety First: Never attempt brake repairs unless you have the necessary knowledge and tools. Incorrect repairs can be dangerous.
* Parts Quality: Use high-quality brake parts from reputable brands. Cheap parts can compromise safety and performance.
* Brake Fluid: While not directly causing pulsation, low or contaminated brake fluid can lead to other brake problems. Check and flush the brake fluid if needed.
By systematically checking these areas, you should be able to pinpoint the cause of your pulsating brakes and get your Ford Expedition back on the road safely. Remember, if you're unsure about any step, seek professional help.
