1979-1985 Buick Riviera Parking Brake Problems and Adjustment

By Core Brake Parts Tech Team — Circleville, OH warehouse

On a 1979-1985 Buick Riviera, parking brake trouble almost always comes down to which rear brakes the car has. Cars built with the optional four-wheel disc system apply the parking brake through a lever on each rear caliper that also self-adjusts the pads, and when that mechanism gets dirty, seized or out of adjustment you get a weak parking brake, a soft pedal, or a rear brake that drags. Cars with rear drums use a conventional cable-to-shoe setup that is adjusted at the shoes first and the cable second.

First, Find Out Which Rear Brakes Your Riviera Has

The 1979 Riviera moved to GM's front-wheel-drive E-body, sharing its chassis with the Oldsmobile Toronado and Cadillac Eldorado. Front disc brakes were standard, and rear discs were an extra-cost option, so a Riviera from this generation can have either rear drums or rear discs depending on how it was ordered. Four-wheel disc cars were common enough that complete stainless line kits are still made specifically for the four-wheel power disc Toronado and Riviera.

Pull a rear wheel and look. A finned drum with a backing plate means drum rear brakes. A rotor with a caliper and a small lever on the back of the caliper, with the parking brake cable hooked to it, means the integral parking brake caliper. Everything below depends on which one you are looking at.

How the Rear Disc Parking Brake Works

The rear calipers on four-wheel disc E-bodies have the parking brake built in. When you step on the parking brake pedal, the cable pulls the lever on the back of each caliper. That lever turns an actuator screw that pushes the piston, and the pads clamp the rotor mechanically, with no hydraulic pressure involved.

The same parts keep the rear pads adjusted as they wear. Each time the parking brake is applied, the lever rotates the actuator screw, and when it is released a ratchet inside the caliper sets the piston in its new position. A return spring lets the pads back off slightly before the ratchet engages, so the brake does not stay applied once you release it. Over many applications this walks the piston outward as the pads wear. The catch is that this adjustment happens when the parking brake lever is worked. A Riviera whose owner never uses the parking brake can end up with rear pads that fall further and further behind.

That is also why these calipers are handled differently at pad time. The piston is threaded onto the actuator screw, so it is turned back into the bore with a caliper piston tool rather than pushed straight in with a C-clamp. Forcing it straight in can damage the internal adjuster.

Symptoms and What They Point To

• Parking brake will not hold the car on a slope. On a disc car, the rear pistons have fallen out of adjustment, the lever or actuator is seized, the cable is stretched or rusted, or the rear pads are worn out. On a drum car, the shoes are too far from the drum or the cable is slack.
• Soft or low brake pedal. When the rear pistons are too far from the rotors, the master cylinder has to push a lot of extra fluid just to bring the rear pads into contact. Increased pedal travel is a classic sign that GM rear calipers of this era have stopped self-adjusting. Air in the lines causes a similar feel, so rule out both.
• Rear brake drags or one rear wheel runs hot. A caliper lever that does not return to its stop, a cable that sticks in its sheath, or a corroded actuator holds the pads against the rotor. Look for a lever that is not resting against its stop with the parking brake released.
• Pedal gets better after pumping the parking brake. That is a strong sign the self-adjusting mechanism works but has not been exercised. If it will not improve at all, the internal ratchet has likely stopped working.
• Parking brake pedal goes nearly to the floor. Excess cable slack, or on drum cars, shoes that have backed away from the drum.

How to Adjust the Rear Disc Parking Brake

Do this with the car safely supported, the rear wheels off, and the parking brake fully released. Use the factory service manual for your exact year as the authority on the procedure and on every torque value.

1. Inspect the pads and rotors first. No adjustment can make up for worn-out rear pads or a rotor worn below its minimum thickness. The minimum is usually stamped on the rotor.
2. Check the levers. With the parking brake released, each caliper lever should rest against its stop. If a lever stays off its stop, the cable is too tight or sticking. Loosen the cable adjuster until both levers return fully.
3. Cycle the levers to bring the pistons out. Work each caliper lever through its travel and let it snap back. First Place Auto Parts, which builds GM-style integral parking brake caliper kits, describes pulling and releasing the lever about 10 to 15 times and watching the piston move out evenly on both sides. You can also do this by applying and releasing the parking brake pedal many times.
4. Check the lever-to-stop gap. For those GM-style calipers, the same guide targets a gap of 1/8 to 1/4 inch between the lever and its stop. Less gap than that risks over-adjusting and dragging.
5. Set cable tension last. Tighten the cable adjuster only until the levers just start to move off their stops, then back it off enough that both levers rest on their stops with the pedal released. A cable adjusted tight enough to hold the levers off their stops will make the rear brakes drag and wear out pads.
6. Verify. Spin each rear rotor by hand. It should turn with only light pad contact. Then road test, and check that the parking brake holds the car on a slope.

If cycling the lever does nothing, meaning the piston does not come out and the pedal does not improve, the internal adjuster is not working. Owners of other GM cars with actuator-screw rear calipers from the same era report the ratchet gets fouled by dirt and stops adjusting. On calipers this old, rebuilding the mechanism is rarely worth it. A remanufactured caliper is the usual fix, and you should replace them as a pair so both sides behave the same. See our rear brake calipers and Cardone remanufactured calipers.

Adjusting a Rear Drum Riviera

On drum-brake cars the parking brake cable works the shoes, so the shoes must be adjusted before the cable. If you tighten the cable to make up for shoes that have backed off, the rear brakes can drag once the shoes are adjusted properly.

1. Release the parking brake completely and loosen the cable adjuster.
2. Remove the drums and check the shoes, the self-adjuster screw and the springs. A seized adjuster screw is the most common reason drum cars lose parking brake and pedal height together. Clean it, lubricate it, and make sure it turns freely.
3. Set the shoes so the drum slides on with light drag. The service manual gives the exact method, and the maximum drum diameter is cast into the drum.
4. Tighten the cable adjuster until the shoes just begin to drag, then back it off until the wheels spin freely with the parking brake released.
5. Apply and release the parking brake several times, then recheck that both wheels turn freely.

Worn shoes, weak springs or a leaking wheel cylinder mean it is time to rebuild the drums. Browse rear brake shoes and brake hardware kits.

What to Replace Together and How Hard the Job Is

For a disc Riviera, replace rear pads as an axle set, and resurface or replace the rear rotors if they are scored, below minimum or causing a pulsation. Check the rear hoses at the same time, because a hose that has collapsed inside can hold pressure on the caliper and look like a parking brake drag. Sticking cables are also common on cars this age, and a new cable is often cheaper than chasing a sticky one. For rear pads we carry the EBC Redstuff ceramic low-dust rear pad set for a quiet, clean street pad, and the EBC Yellowstuff rear pads for owners who want more bite and heat resistance. See also our brake rotors and brake hoses.

Difficulty: adjusting a healthy disc parking brake is an easy driveway job. Rear pads on the integral calipers are moderate, because the piston has to be wound back in and the parking brake set up afterward. Replacing calipers is moderate too, and means bleeding the brakes. Use fresh fluid of the type shown on the master cylinder cap or in the owner's manual. Drum brake overhauls are moderate but fiddly because of the springs. If the pedal is still soft after correct adjustment and bleeding, have the master cylinder checked. Our master cylinders are listed by fitment.

Frequently Asked Questions

Does my 1979-1985 Riviera have rear disc brakes?

Maybe. Front discs were standard, and rear discs were an extra-cost option, so these cars came either way. Pull a rear wheel: a caliper with a cable-operated lever means rear discs with an integral parking brake, and a drum means drum brakes.

Why is my brake pedal soft even though the front brakes are new?

On a four-wheel disc car, the most common cause is rear caliper pistons that have fallen out of adjustment, so the pedal has to move a lot of fluid before the rear pads touch. Work the parking brake repeatedly to let the self-adjusters take up the slack. If the pedal does not improve, check for air in the system and for a seized rear adjuster.

How many times should I pump the parking brake to adjust it?

There is no single number. The goal is for the rear pistons to come out until the lever-to-stop gap is right and the pedal is firm. One maker of GM-style integral calipers describes 10 to 15 lever cycles for an initial setup. If many cycles make no difference, the adjuster is not working.

Can I push the rear caliper piston back with a C-clamp?

No. On these integral parking brake calipers, the piston is threaded onto the actuator screw and has to be rotated back in with a caliper piston tool. Pushing it straight in can damage the adjuster.

Should I replace both rear calipers if only one is bad?

Yes, on a car this old. The two sides share the parking brake cable, and a new caliper paired with a tired one tends to adjust unevenly, which gives uneven parking brake hold and uneven pad wear.

Why does my parking brake drag after I tightened the cable?

The cable was probably used to make up for rear pistons or shoes that were out of adjustment. Back the cable off until the caliper levers rest on their stops, or on drum cars until the shoes clear, then adjust the brakes themselves before resetting cable tension.

Sources

1. Conceptcarz - 1979 Buick Riviera - front discs standard, rear discs an extra-cost option
2. Inline Tube - 1979-85 Toronado/Riviera four-wheel power disc brake line kit - four-wheel disc configuration on 1979-85 Toronado and Riviera
3. First Place Auto Parts - How to Adjust Rear Disc Brake Caliper Parking Brake Mechanism - 10 to 15 lever cycles and 1/8 to 1/4 inch lever-to-stop gap for GM-style integral calipers
4. ThirdGen.org - Adjusting Rear Disc Brakes - how the GM actuator-screw, ratchet and return-spring design of the era self-adjusts through the parking brake, why dirt stops it working, and increased pedal travel as the symptom