1975-1978 Nissan 280z Brake Noise: Squeal, Grinding and Pulsation Causes

By Core Brake Parts Tech Team — Circleville, OH warehouse

Most brake noise on a 1975-1978 Nissan 280Z comes from one of three places: a front pad that has lost or never had its anti-squeal shims and damper springs, pads or drum shoes worn down to metal, or thickness variation in the front rotors that you feel as a pulsing pedal. The car uses Girling-Sumitomo two-piston fixed calipers up front and leading-trailing drum brakes in back, so the diagnosis is different from a modern sliding-caliper car. Here is how to tell which problem you have and what fixes it.

How the 280Z Brake System Works

Every 1975 through 1978 280Z uses the same basic layout. The factory service information describes a tandem master cylinder feeding two separate hydraulic circuits, a Master-Vac vacuum power booster, front disc brakes with Girling-Sumitomo dual-piston fixed calipers, and rear leading-trailing shoe drum brakes. A proportioning valve limits rear line pressure so the rear wheels do not lock before the fronts.

Two design details matter for noise diagnosis:

• Fixed front calipers. The caliper body is bolted solid to the strut and has a piston on each side of the rotor. There are no slide pins to seize. Instead, each pad is held in the caliper by retaining pins, clips and damper springs, and the pads carry anti-squeal shims on the back of the backing plate. When those small parts are missing, worn or rusted, the pad is free to vibrate.
• Self-adjusting rear drums worked by the parking brake. The service manual notes the rear shoes adjust themselves when the parking brake is applied. On a car that rarely has its parking brake used, the shoes can sit further from the drum than intended. The rear drums are finned aluminum with cast-iron liners, so a shoe worn to the rivets or backing will cut into that liner quickly.

Squeal: Causes and Diagnosis

A high-pitched squeal is vibration. Wagner's brake noise guidance puts it plainly: vibration is the main source of brake noise, and it usually traces to rust, distorted or loose components, or worn and weakened original parts. On a 280Z, check these in order:

1. Anti-squeal shims. Pull the retaining pins and slide the front pads out. Each pad should have its shim on the back of the backing plate, facing the piston. Shims get lost during pad changes on older cars all the time. No shim, or a rusted and delaminated one, is the most common cause of squeal on these calipers.
2. Damper springs and retaining pins. These keep the pad from rattling and chattering in the caliper. Replace them if they are bent, weak or corroded. A new brake hardware kit is inexpensive insurance on a car this age.
3. Pad glazing or poor bedding. Pads that were never bedded in, or were overheated, develop a hard glazed surface that sings. Wagner recommends a burnish of 20 slow-downs from 50 mph to 20 mph with light pedal pressure, waiting at least 30 seconds between them.
4. Dust and rust on the rotor and hub. Wagner lists hub-surface rust and dust buildup as noise sources. New rotors should be washed with soap and water and a bristle brush before installation to lift machining residue out of the surface finish.
5. Wear indicators. If the pads have a metal wear tab, a steady squeal while driving that changes when you press the pedal can be the tab touching the rotor. That means the pads are due.

On lubrication: if the pads come with a constrained-layer shim already attached, Wagner advises only a light coat of silicone brake lubricant on the back of the shim, and warns against tacky compounds that can pull the shim off the plate. Do not put any lubricant on the pad friction surface or the rotor face.

Grinding: Causes and Diagnosis

Grinding is more urgent than squeal because it usually means metal is touching metal.

• Front pads worn out. The ZCarGuide front brake procedure calls for new pads once the friction material is down to 3/32 in. (2.4 mm) or less. Below that, the steel backing plate is not far from the rotor. Look through the caliper opening with the wheel off and compare both pads on each side; a fixed caliper can wear its inner and outer pads unevenly if one piston is sticking.
• Rear shoes worn to the rivets or backing. Because the rear drums rely on parking-brake use to adjust, a neglected car can go a long time without anyone looking at the shoes. Grinding from the rear on a 280Z deserves immediate attention, since the cast-iron liner inside the aluminum drum is what the shoe rides on.
• Debris or a rusted dust shield. A stone caught between the rotor and the splash shield, or a rotted shield rubbing the rotor, makes a grinding or scraping sound that does not change with pedal pressure.
• Wheel bearings. Wagner lists loose or improperly adjusted wheel bearings as a noise source. A growl that changes when you swerve left and right, not when you brake, points to a bearing rather than the brakes.

If grinding has already scored the rotor or drum liner, replace the friction parts and the metal part together. Fresh brake pads on a gouged rotor will not seat, and will be noisy from the first stop.

Pulsation: Why the Pedal Pulses

A pedal that pulses or a steering wheel that shakes during stops is almost always rotor thickness variation, not a literally warped rotor. A tech tip from Akebono Brake Corp., published in Brake and Front End, explains the mechanism: lateral runout lets the pads brush the high spots of the rotor on every revolution, even when you are not braking, and over thousands of miles that contact turns into uneven thickness. Akebono states a new vehicle's mounted lateral runout can be as high as 50 microns (0.002 in.), and that only about 10 to 20 microns (0.0004 to 0.0008 in.) of thickness variation is enough for a driver to feel.

The same tip notes unibody cars with strut suspension are more sensitive to this, which describes the 280Z. On this car also check:

• Hub face condition. Rust or scale between the hub and rotor adds runout. Clean the mounting face to bare metal before installing a rotor.
• Wheel bearing adjustment. Loose bearings let the rotor wobble, which feeds runout.
• Out-of-round rear drums. A pulse you feel mostly through the seat, or only when using the parking brake, can come from the rear drums rather than the front rotors.
• Uneven lug nut tightening. Tighten lug nuts in a star pattern to the factory value with a torque wrench, not an impact gun.

The fix is to replace or resurface the front brake rotors, clean the hub mounting surface, check runout with a dial indicator against the limit in the factory service manual, and bed in the new pads properly.

Quick Symptom Table

What to Replace at the Same Time

On a car this old, rubber and small hardware age out regardless of mileage. When you are in the brakes for noise, it is worth doing the following together:

• Front pads with new shims, retaining pins and damper springs.
• Front rotors if they are scored, below minimum thickness, or causing pulsation.
• Rear brake shoes and the return and adjuster springs if the shoes are worn or the self-adjuster is sticking.
• Flexible hoses. Old rubber hoses can deteriorate inside and hold pressure on one caliper, which causes dragging, heat, glazing and noise on that side. A Russell stainless braided brake line kit for the 1975-1978 280Z replaces them with lines that resist swelling. More options are in our brake lines collection.
• Brake fluid. Flush with the fluid type shown on the reservoir cap or in your owner's manual whenever the system is opened.

Difficulty: front pads on the fixed Sumitomo calipers are a beginner job, because the pads slide out after the retaining pins are pulled without removing the caliper. Rotors are a moderate job because the caliper has to come off and the hub must be serviced. Rear shoes are moderate as well, mainly because of the springs and the parking brake linkage.

Frequently Asked Questions

Do 1975-1978 280Z models have rear disc brakes?

No. The factory service information lists leading-trailing shoe drum brakes at the rear for these years, with front disc brakes using dual-piston fixed calipers.

Why do my new 280Z pads squeal?

The usual reasons are that the old anti-squeal shims were not reused or replaced, the pads were not bedded in, or the rotors were not cleaned after resurfacing. Check that each pad has its shim and damper spring, then do a proper burnish.

Are my 280Z rotors warped if the pedal pulses?

Usually not warped in the literal sense. The common cause is thickness variation that builds from lateral runout over time. Replacing or resurfacing the rotors and cleaning the hub face is the fix.

Can I grease the back of the pads?

If the pads have shims attached, a light coat of silicone brake lubricant on the back of the shim is fine. Never put anything on the friction surface or rotor, and avoid tacky compounds that can pull the shim loose.

Why does my 280Z make noise from the rear only?

Check the rear shoes for wear and adjustment. The rear brakes self-adjust through the parking brake, so a car whose parking brake is rarely used can have loose, noisy or worn shoes that nobody has inspected.

Sources

1. Datsun 280Z 1975 brake service information - Girling-Sumitomo dual-piston fixed calipers, leading-trailing rear drums, proportioning valve, parking-brake self-adjusters, pad shims and damper springs
2. Datsun 280Z 1976-77 brake service information - same caliper and rear drum layout for later years, Master-Vac booster, tandem master cylinder
3. ZCarGuide S30 front brake replacement guide - 3/32 in. (2.4 mm) pad replacement threshold, anti-squeal shims, finned aluminum rear drums with cast-iron liners
4. Wagner Brake: brake system noise - vibration as the source of noise, shim lubrication, rotor cleaning, 20-stop burnish procedure
5. Akebono tech tip via Brake and Front End: diagnosing pedal pulsation - thickness variation mechanism and runout figures