Brake hydraulics and the servo

The E-Type uses disc brakes at all four wheels, with the rear discs mounted inboard on the differential. That layout saves unsprung weight, but it also means the rear brakes run hotter and are harder to reach than outboard discs. Most of the brake problems that show up on a road test come from the hydraulic circuit, the servo or the inboard rears rather than from worn front pads.

What the hydraulic system asks for

Brake fluid is hygroscopic, which means it absorbs moisture from the air over time. Moisture lowers the boiling point of the fluid and promotes corrosion inside the master cylinder, calipers and the servo. Old fluid is one of the cheapest things to replace and one of the most commonly skipped. A firm pedal that stays firm is good; a pedal that sinks, goes spongy or creeps towards the floor is telling you something about the seals or the fluid condition.

Common faults

• A hard pedal that needs a lot of effort often points at a failed or leaking servo, or at the vacuum supply to it. The brakes still work, but they no longer have assistance.
• A spongy pedal usually means air in the lines, swollen flexible hoses or a master cylinder fault. The inboard rear calipers are a particular nuisance to bleed properly.
• A pedal that fades or sinks under pressure points at worn master-cylinder seals.
• Inboard rear discs can seize if the car is little used, and the handbrake mechanism can bind because of the long cable run.
• Brake drag or a hot rear axle after a run can mean the rear calipers are not releasing cleanly.

Servo checks

The servo uses inlet-manifold vacuum to reduce pedal effort. A leaking servo can hiss, affect idle speed or allow brake fluid to find its way into the vacuum hose. Servo units can be reconditioned or replaced with specialist parts. A car with a hard pedal and poor idle should have the servo and its vacuum line inspected before the rest of the system is condemned.

Maintenance priorities

Flush the brake fluid on a schedule that matches use and fluid condition rather than mileage alone. Inspect flexible hoses for cracking and for ballooning under pressure. Check the front pads and discs through the wheels, and use inspection holes or a mirror to look at the inboard rears. A brake system that pulls, squeals or overheats is giving early warning; on a car with inboard rear brakes, the warning is worth acting on before the calipers seize.