* Proportioning Valve Issues: This valve controls the brake pressure balance between the front and rear brakes. If it's malfunctioning (stuck, leaking internally, or simply worn out), it might send too much pressure to the rear brakes, causing them to lock up, especially during hard braking. This is a very common cause in older vehicles.
* Worn or Damaged Rear Brake Shoes/Pads: Severely worn or unevenly worn brake shoes (drum brakes) or pads (disc brakes, if so equipped – some 2001 Trackers had rear drums, others discs) can lead to grabbing and locking. One side being worn more than the other is a strong indicator.
* Seized Wheel Cylinders (Drum Brakes): If your Tracker has rear drum brakes, the wheel cylinders can seize due to corrosion or internal damage. This prevents the brake shoes from retracting properly, leading to constant or intermittent braking.
* Seized Calipers (Disc Brakes): If it has rear disc brakes, seized calipers prevent the brake pads from releasing, resulting in the wheels locking up. This can be caused by corrosion, a sticking piston, or a failed caliper boot.
* Parking Brake Cable Issues: A partially engaged or stuck parking brake cable can also contribute to rear wheel lockup, even when the service brake isn't applied.
* Master Cylinder Issues: While less likely to cause *only* rear brakes to lock, a failing master cylinder can send inconsistent pressure to the braking system, possibly leading to this problem. This is more likely to affect both front and rear brakes though.
* Low Brake Fluid: While low fluid usually affects all brakes, it could exacerbate existing problems like a sticking caliper or wheel cylinder.
What to do:
1. Don't drive the vehicle until the problem is fixed. Locked rear brakes are extremely dangerous.
2. Inspect the brake system: Look for obvious signs of damage, leaks, or wear. Check the brake pads/shoes for wear and evenness. Look at the brake lines and hoses for leaks or damage.
3. Check the parking brake: Make absolutely sure it's fully released.
4. Have a professional mechanic inspect the vehicle: This is crucial. They have the tools and expertise to diagnose the problem accurately and safely repair it. They can properly check the proportioning valve, wheel cylinders/calipers, and other components to pinpoint the root cause.
Ignoring this problem is dangerous and could lead to an accident. Get it checked out as soon as possible.
