1979-1980 Cadillac Seville Brake Caliper Problems and Replacement

By Core Brake Parts Tech Team — Circleville, OH warehouse

Most caliper trouble on a 1979-1980 Cadillac Seville shows up at the rear. Both model years use four-wheel disc brakes, and the rear calipers carry a built-in parking brake mechanism that also acts as the rear self-adjuster. When that mechanism seizes or falls out of adjustment you get a low or sinking pedal, a weak parking brake, or a rear brake that drags. The fix is usually a pair of rear calipers, fresh pads and a careful parking brake lever adjustment before the first pedal stroke.

How the Seville brake system is built

The 1979 Seville was the last year of the original rear-wheel-drive car, powered by a 5.7-liter Oldsmobile V8 with a three-speed automatic. For 1980 the Seville was redesigned on a front-wheel-drive platform. Despite the change underneath, both years share the same basic brake layout: disc brakes at all four wheels, a dual master cylinder with separate front and rear fluid chambers, and a tandem vacuum power booster. Period specifications for the 1979 car list single-piston sliding calipers with ventilated rotors at every wheel.

The rear caliper is the part that makes these cars different from a typical 1970s sedan. Instead of a separate drum-in-hat parking brake, the parking brake cable pulls a lever on the rear caliper itself. The lever turns a threaded shaft inside the caliper that drives the piston out and clamps the pads against the rotor. That same threaded mechanism takes up pad wear, which is why these calipers are described as self-adjusting through parking brake use. The 1980 and later Seville rear caliper, with the lever on top, became so well known that hot rodders still bolt it onto other rear axles when they want rear discs with a working parking brake.

Because 1979 and 1980 sit on different platforms, rear calipers, pads and hardware do not automatically interchange between the two years. Always match parts to the exact year, engine and axle before ordering.

Symptoms of a failing Seville caliper

A simple check from one caliper maker's instructions: with the wheel off, grab the rear pad and try to shake it. If it rattles, the parking brake lever is out of adjustment. A pedal that is low and spongy, or that pumps up, points to air in the system instead.

Why these calipers fail

The biggest cause is simply not using the parking brake. The rear self-adjuster only works when the lever cycles, so a Seville that is parked in gear for years with the brake off never adjusts its rear pistons. Over time the internal threads and lever shaft corrode and seize, and the caliper can no longer adjust at all. The result is a piston that retracts too far and uses up most of the pedal travel before the rear pads even touch the rotor.

Age is the second cause. These cars are now more than 40 years old. Rubber piston seals and dust boots harden, moisture in old brake fluid rusts the bores, and slide pins stop sliding. A caliper that has sat for years can look fine and still hang up once it gets hot. Old brake hoses can also collapse inside and act like a check valve, holding pressure on a caliper so it drags even when the caliper itself is healthy.

The fix: which parts to replace

Replace calipers in pairs on the same axle so both sides clamp and release evenly. For the rear, buy calipers that include the parking brake lever and mechanism, and confirm the lever position and bracket match your year. Remanufactured and new units are both available in our brake calipers collection; a Cardone remanufactured caliper is a common route for older GM applications.

While the calipers are off, it pays to do these at the same time:

• Pads. New calipers deserve new pads on both sides of the axle. For the rear we carry the EBC Bluestuff NDX rear brake pads for the 1979-1980 Seville 5.7L; see all options in our brake pads collection.
• Rotors. Measure thickness against the minimum stamped on the rotor. Resurface or replace if they are under spec, scored or warped. Shop brake rotors.
• Hoses. Rubber hoses of this age are overdue. Replace any hose that is cracked, swollen or suspected of collapsing. See brake hoses.
• Hardware. Clips, pins and bushings wear with the caliper. A brake hardware kit keeps the new calipers sliding freely.
• Fluid. Flush the whole system with the brake fluid type printed on the master cylinder cap or in the owner's manual. Old fluid is what rusted the bores in the first place.
• Parking brake cables. A seized or stretched cable will defeat a new caliper's self-adjuster.

How hard is the job, and the step people skip

Front caliper replacement is a routine driveway job: support the car safely, remove the wheel, unbolt the caliper, swap pads and hardware, and torque the bolts to the values in the factory service manual. The rear is where this car demands attention.

The rear piston is driven by the threaded parking brake mechanism, so it is not simply pushed back with a clamp the way a front piston is. Follow the retraction procedure supplied with the caliper, and do not force it.

After the rear calipers are installed, the parking brake lever must be adjusted before you press the brake pedal. Aftermarket caliper instructions describe disconnecting the cable and cycling the lever forward and back until it only moves a short distance off its stop each time; follow the travel figure given in the instructions for the calipers you install, since suppliers state different figures. Skipping this step can leave you with no parking brake, a low pedal, and dragging or overheating rear brakes.

Bleeding is the other trap. Air rises, so the bleeder must be at the highest point. One bracket and caliper supplier notes that normal bleeding may still leave a soft pedal on these parking brake calipers, and recommends taking the calipers off their brackets and gravity bleeding them with the bleeder pointing up, tapping the caliper to knock bubbles loose. Once done, the pedal should be high and hard. If it is low and spongy or pumps up, there is still air in the system.

Overall, a DIYer comfortable with brakes can do the front in an afternoon. The rear calipers are a moderate job that rewards patience; if you cannot get the levers to adjust or the pedal to come up firm, have a brake shop finish it.

Keeping the new calipers healthy

Use the parking brake every time you park. On these calipers, that is not a suggestion: regular parking brake use is what keeps the rear pistons adjusted and the lever threads moving. A collector car that sits for months should still have its parking brake cycled a few times whenever it is started. Flush the fluid on a regular schedule so moisture does not rust the new bores, and check that each rear lever returns to its stop when released.

NHTSA's recall database shows a 1980 Seville recall for the transmission gear position indicator linkage, not for the brakes, so caliper problems on these cars are wear and age items rather than a factory defect with a free fix.

Frequently Asked Questions

Why does my Seville brake pedal keep getting lower?

The most common reason is that the rear caliper self-adjusters are not working. They adjust through parking brake use, so if the parking brake is never set, or the lever shafts are seized, the rear pistons retract too far and the pedal sinks. Air in the lines or a failing master cylinder can also cause it.

Do 1979 and 1980 Seville rear calipers interchange?

Do not assume they do. The 1979 is rear-wheel drive and the 1980 was redesigned on a front-wheel-drive platform. Match the caliper to your exact year and verify the lever position and mounting before installing.

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

No. The rear piston is linked to the threaded parking brake mechanism. Use the retraction method in the caliper's instructions; forcing it can damage the adjuster.

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

Yes. Replacing calipers in axle pairs keeps clamping force, release and self-adjustment even side to side. On a car this old, the other side is usually close behind.

Why is my parking brake weak after new rear calipers?

The levers were probably not adjusted before the pedal was pressed, or the cables are stretched or seized. Recheck lever travel against the caliper instructions and inspect the cables.

Sources

1. NotoriousLuxury - 1979 Cadillac Seville - four-wheel disc brakes, single-piston sliding calipers, ventilated rotors, dual master cylinder, tandem booster, 5.7L V8 and three-speed automatic
2. Speedway Motors - rear disc bracket kit instructions - 1980-85 Seville rear caliper with parking brake, lever adjustment, low pedal cause, gravity bleeding
3. TSM / Rustic Disc Brakes - rear caliper parking brake lever adjustment - adjust before applying hydraulic brakes, pad rattle test, consequences of skipping adjustment
4. CPP - adjusting the Cadillac caliper parking brake lever - integral self-adjusting parking brake, dragging and overheating when not adjusted
5. NHTSA recalls - 1980 Cadillac Seville - only recall listed is for the gear position indicator, not brakes