2004-2008 Chevrolet Impala Parking Brake Problems and Adjustment

By Core Brake Parts Tech Team — Circleville, OH warehouse

On a 2004-2008 Chevrolet Impala the parking brake is not built into the rear calipers. It is a small set of drum brake shoes hidden inside the hat (center section) of each rear rotor, pulled on by cables from the foot pedal. When the parking brake stops holding, the cause is almost always shoe clearance, worn or contaminated shoes, or cables and an equalizer that have stretched or rusted, and the fix is to adjust the shoes first and the cable second.

How the Impala Parking Brake Works

Both generations in this range, the 2004-2005 Impala and the redesigned 2006-2008 car, use four-wheel disc brakes. Published specifications list front rotors of 11.93 x 1.26 in. and rear rotors of 10.9 x 0.43 in. for the 2004 model, and 11.9 x 1.2 in. front and 10.9 x 0.4 in. rear for the 2006 model, with no rear drums listed for either year. GM's genuine parts catalog lists one rear parking brake shoe kit for the 2000-2010 Impala, covering every engine from the 3.4L and 3.5L V6 through the 3.9L V6 and the 5.3L V8 in the SS.

That layout is called drum-in-hat. The inside of the rotor's hat is machined as a small brake drum. Two shoes sit on a backing plate behind it, held by a pin and spring. A cable-operated lever and cam spread the shoes against the drum surface when you press the pedal. The hydraulic calipers and pads only do the stopping; the shoes only do the holding.

Common Symptoms and What They Point To

• Car rolls with the parking brake set. The classic complaint. Owners have filed NHTSA reports on this platform describing a parking brake that would not hold on an incline, including one 2006 owner whose brake stopped holding again within a couple of months after two dealer visits. That pattern usually means the shoes were never set to the correct clearance, or the cable was tightened to hide a shoe problem.
• Pedal goes almost to the floor. Excess shoe-to-drum clearance or a stretched cable. Brake and Front End magazine notes that parking brake cables stretch over time, adding slack that increases pedal travel, and that a cable with all of its adjustment used up should be replaced.
• Normal pedal travel but no holding power. Look at the equalizer under the car. A rusted or broken equalizer pivot can give a pedal that feels right while the shoes barely move.
• Rear brake drag, heat or a burning smell after a parking brake service. Shoes set too tight, or a cable that is seized and not letting the shoes retract.
• Grinding or scraping from the rear at low speed. A broken shoe spring or lining that has come loose inside the hat. Pull the rotor and look.

One more thing to rule out: if the car is hard to shift out of Park on a slope, that is driveline load on the transmission parking pawl, not a brake defect. Setting the parking brake before shifting into Park takes that load off the transmission, and it only works if the parking brake actually holds.

Why the Parking Brake Stops Holding

1. Shoes are out of adjustment. As the lining wears, the gap to the drum grows and the cable cannot take it all up.
2. Rust on the drum surface. The hat sees little use on a car that is rarely parked with the brake set. Surface rust glazes the drum and the shoes lose grip.
3. Contaminated shoes. Grease or a leaking rear seal can soak the lining. Contaminated shoes do not come back; replace them.
4. Stretched, kinked or seized cables. Salt-belt cars are hard on the rear cables and the equalizer.
5. Wrong order of adjustment. Tightening the cable at the equalizer to make up for loose shoes gives a brake that works for a few weeks and then fades again.

How to Adjust It the Right Way

The rule is shoes first, cable second. Brake and Front End describes the general drum-in-hat method: the shoes are adjusted with a star wheel at the top of the backing plate, reached through an access slot in the rotor hat with a brake spoon, turning the rotor while expanding the shoes until they drag, then backing off until the rotor turns free. It also notes that some manufacturers specify a drum diameter gauge to set the exact shoe-to-drum gap instead of going by feel. If your factory service manual calls for the gauge, use it.

1. Chock the front wheels, raise the rear and remove the rear wheels.
2. Release the parking brake fully and make sure the pedal returns all the way.
3. Remove the rear caliper and bracket, hang the caliper by a wire (never by the hose), and pull the rotor.
4. Inspect the shoes, springs and the drum surface in the hat. Clean light rust off the drum. Replace soaked, cracked or thin shoes as a set on both sides.
5. Set the shoe-to-drum clearance with the gauge, or with the star wheel by the drag-then-back-off method.
6. Reinstall the rotors, caliper brackets and calipers. Torque the bracket and caliper bolts to the values in the factory service manual.
7. Only now take slack out of the cable at the equalizer, until the rear wheels just begin to drag, then back it off so both wheels spin free with the pedal released.
8. Apply the pedal and confirm both rear wheels lock. Release and confirm both spin freely.

New shoes should be burnished before you rely on them. Follow the shoe maker's bedding instructions, which typically call for a few gentle, low-speed applications in a safe, empty area. That beds the lining into the drum surface so the brake holds at full strength.

Parts to Replace at the Same Time

Because the rotor has to come off for any parking brake work, it is the ideal time to deal with the rear service brakes too. If the rotors are below minimum thickness or the hat drum is scored, replace them; new rear brake rotors give the shoes a fresh drum surface. Fit new rear brake pads if they are near the wear limit, and a brake hardware kit for the pad clips and shoe springs, which lose tension with heat and age. Check the rear brake calipers for torn boots and sticking slide pins while they are off. Replacement parking brake shoes are in our brake shoes collection.

While you are under the car, check the 2004 recall history: NHTSA campaign 04V287000 covered certain vehicles built with low torque on the front caliper-to-knuckle bolts. It is a front-brake item, not a parking brake one, but any 2004 Impala should have it confirmed as completed.

How Hard Is the Job?

For someone who has done a rear pad and rotor job, this is a moderate driveway job. The hardest part is usually a rotor rusted to the hub, and on salt-belt cars, a cable or equalizer that is seized. The shoe springs take patience to reinstall. If you do not have a way to measure the drum, or the drag-and-back-off method gives uneven results side to side, a shop with the right gauge will get it right the first time.

Frequently Asked Questions

Does the 2004-2008 Impala have rear drum brakes?

No. All years in this range have rear disc brakes. The only drum surface is the small one inside each rear rotor's hat, used by the parking brake shoes.

Can I fix a weak parking brake by tightening the cable?

Only if the shoes are already correctly adjusted. Tightening the cable to make up for loose shoes is a short-term fix and can cause drag. Adjust the shoes first.

Do I need to replace the rotors to replace the parking brake shoes?

Not always, but the rotor must come off to reach the shoes. If the hat drum surface is scored, glazed or worn past spec, replace the rotor.

Why does my parking brake work after a service and then fade again?

Usually the cable was tightened instead of the shoes being adjusted, or the shoes were contaminated or never burnished. A seized cable or equalizer can do the same.

Are the parking brake shoes the same for the 2004 and 2008 Impala?

GM's catalog lists one rear parking brake shoe kit covering the 2000-2010 Impala, but always confirm fitment by your VIN or by matching the old part before ordering.

Sources

1. Brake and Front End - Adjusting Parking Brakes - drum-in-hat layout, star-wheel adjustment, drum gauge, cable stretch and equalizer failure
2. The Car Connection - 2004 Chevrolet Impala specifications - four-wheel disc brakes and rotor sizes
3. The Car Connection - 2006 Chevrolet Impala specifications - four-wheel disc brakes and rotor sizes
4. GM genuine parts catalog - Impala parking brake shoe - rear parking brake shoe kit listed for 2000-2010 Impala, all engines
5. NHTSA complaints - 2006 Chevrolet Impala - owner report of a parking brake that would not hold after repeated service
6. NHTSA recalls - 2004 Chevrolet Impala - campaign 04V287000, front caliper bolt torque