1975-1978 Nissan 280z Brake Caliper Problems and Replacement

By Core Brake Parts Tech Team — Circleville, OH warehouse

The 1975-1978 Nissan (Datsun) 280Z stops with a two-piston fixed caliper on each front wheel and leading-trailing drum brakes at the rear. After four-plus decades, the most common front caliper problems are pistons seized by internal corrosion, torn dust seals, and swollen rubber hoses that trap pressure. The fix is either a caliper rebuild with new seals or a bolt-on new or remanufactured caliper, done as a pair with fresh pads, hoses and fluid.

How the 280Z Front Brakes Work

The factory repair information for the 1975 280Z describes the front brakes as a Girling-Sumitomo dual-piston fixed caliper disc type. Fixed means the caliper body bolts rigidly to the steering knuckle and does not slide; one piston sits on each side of the rotor and squeezes its pad inward. There are no slide pins to seize, which is one less failure point than on a modern floating caliper, but it also means each side of the caliper depends entirely on its own piston moving freely.

The pads are held in the caliper by two retaining pins with spring clips, so pad changes do not require unbolting the caliper from the knuckle. The system is power assisted, split into separate front and rear hydraulic circuits by a tandem master cylinder, and uses a proportioning valve to keep the rear drums from locking before the fronts. Front disc brakes are self-adjusting; the rear drums adjust themselves through the parking brake.

Symptoms of a Bad 280Z Caliper

• Pulling to one side under braking. A piston that is stuck retracted gives that wheel less braking force, so the car pulls toward the good side. A piston stuck applied pulls toward the bad side even off the brake.
• One hot wheel after a drive. Carefully compare wheel temperature side to side after a short drive. A dragging caliper runs noticeably hotter and can smell of burning friction material.
• Uneven pad wear. On a fixed caliper, the inner and outer pads should wear about equally. One pad worn far thinner than its partner points to a lazy piston on the other side.
• Wheel drags when spun by hand. With the car safely on stands and the transmission in neutral, a front wheel should turn with only light pad contact.
• Fluid on the inside of the wheel or a torn dust boot. Wetness around the piston or a split boot means the seal has failed or is about to, and water is getting to the piston.
• Low or soft pedal. A leaking seal or a deteriorated hose can both show up as a pedal that sinks or feels spongy.

Why Calipers Fail on a Car This Old

Moisture in the fluid. Brake fluid absorbs water over time, and that water corrodes the caliper bore and piston from the inside. Pitting in the bore binds the piston so it will not retract, or will not move at all. Cars that sat for years with the same fluid are the worst cases, which describes a lot of surviving 280Zs.

Torn dust seals. Once the outer dust seal splits, road water reaches the exposed part of the piston. Rust on the piston face then drags on the seal every time the brakes release.

Collapsed rubber hoses. The flexible hose between the hard line and the caliper deteriorates internally. A failing hose can act like a one-way valve, letting pressure in but not back out, which looks exactly like a seized caliper. Always check the hose before condemning the caliper.

Previous poor repairs. Pistons pushed back crooked or with too much force, or cleaned with the wrong solvent, damage seals. The factory procedure warns against mineral-based solvents and against using abrasives on the plated piston surface.

Rebuild or Replace the Caliper?

Both are valid on the 280Z. The factory overhaul procedure is straightforward: remove the retaining ring and dust seal, hold one piston with a wood block while low air pressure through the inlet pushes the other out, clean everything in alcohol or brake fluid, inspect the bores and pistons, then reassemble with new rubber parts coated in rubber grease. A rebuild makes sense if the bores and pistons are clean and smooth.

If a bore is pitted or a piston is rusted, a replacement caliper is the better call. Stock-replacement new and remanufactured front calipers for the 1970-1978 240Z, 260Z and 280Z are sold by side (left or right) and bolt on without modification. Browse replacement brake calipers and pick the correct side for each wheel. Whichever route you take, do both front calipers so the car brakes evenly.

What to Replace at the Same Time

• Front pads. Contaminated or unevenly worn pads should never go back in. The Hawk HPS HB169F.560 is one front pad listed for the 1975-1978 280Z; see our brake pads and ceramic brake pads for options.
• Rotors. A dragging caliper often overheats and scores the rotor. Measure it against the minimum thickness in the factory service manual, and replace it if it is under spec, heat-checked or grooved. Shop brake rotors.
• Flexible brake hoses. On a car this age, the rubber hoses are almost always due. A stainless braided set such as the Russell Street Legal stainless braided brake line kit for the 1975-1978 280Z replaces the hoses in one purchase and removes a common cause of false seized-caliper diagnoses.
• Pad retaining pins and clips. Replace rusted pins and weak clips; a brake hardware kit is cheap insurance.
• Brake fluid. Flush the whole system with the fluid type specified on the master cylinder cap or in the owner's manual. Old fluid is what corrodes caliper bores in the first place.

How Hard Is the Job?

This is a reasonable DIY job for someone with jack stands, a flare-nut wrench and a torque wrench. Removing a caliper means disconnecting and plugging the hydraulic line, then removing the mounting bolts that hold it to the steering knuckle. Pads slide out once the retaining pins and clips are removed. Torque the caliper mounting bolts to the value in the factory service manual, and use new sealing washers at the hose connection.

The step people rush is bleeding. Because the front and rear circuits are separate, bleed every wheel until the fluid runs clean and bubble-free, then confirm a firm, high pedal before driving. Bed in the new pads with a series of moderate stops before any hard braking. If the car still pulls after new calipers and hoses, check the rear drums and the proportioning valve next.

Frequently Asked Questions

Are the 280Z front calipers the same as the 240Z and 260Z?

Stock-replacement front calipers are sold as fitting the 1970-1978 240Z, 260Z and 280Z, and the Hawk HB169F.560 front pad is listed for all three. Rotors can differ by model, so confirm the rotor part for your exact car.

Does the 280Z have rear disc brakes?

No. The 1975-1978 280Z uses self-adjusting leading-trailing drum brakes at the rear. Rear disc setups on these cars are aftermarket conversions.

How do I know if it is the caliper or the brake hose?

If a wheel drags, crack the bleeder on that caliper. If the wheel frees up immediately, pressure was trapped, which often points to a collapsed hose. If the piston still will not move, the caliper itself is seized.

When should I replace the front pads?

Replace them when the friction material is 2.4 mm (3/32 in.) thick or less, or sooner if one pad is worn much more than its partner.

Should I replace calipers in pairs?

Yes. Replacing or rebuilding both front calipers at the same time keeps braking force even from side to side, so the car stops straight.

Sources

1. Datsun (Nissan) 280Z 1975 Brake Repair Manual - Girling-Sumitomo dual-piston fixed caliper, overhaul procedure, rear drum type, proportioning valve
2. ZCarGuide S30 front brake replacement guide - disc/drum layout, tandem master cylinder, pad retaining pins, 2.4 mm pad limit
3. Z Car Depot front brake caliper 240Z/260Z/280Z - stock-replacement calipers for 1970-1978 sold by side
4. Hawk Performance HB169F.560 - front pad application for the 280Z
5. Phoenix Systems: what causes a caliper piston to stick - moisture corrosion, seals, hose restriction, symptoms