MGB GT

1965-1980 / Coupe / United Kingdom

All MGB GT problems All workshop problems

Minor Brakes

Brake Servo Failure (Later Cars)

Symptoms

Hard brake pedal with dramatically reduced braking assistance. In the worst cases, reported by MGB Register members, fluid can leak internally into the servo canister -- the pedal feels normal until you press it, then all the fluid disappears into the servo and you have no brakes at all.

Cause

The servo diaphragm deteriorates with age and heat. The vacuum hose perishes. On rubber bumper cars, the servo is mounted in the engine bay between the pedal box and master cylinder, exposed to significant heat.

Fix

Replace the servo unit ($150--300).

Check the vacuum hose and one-way valve.

If the servo has failed catastrophically (fluid leaking internally), the car must be towed, not driven.

Cost mentioned in fix

$150

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Other known issues

Minor Brakes

Brake Master Cylinder Failure

A spongy brake pedal that sinks to the floor under sustained pressure. Brake fluid weeping from the master cylinder body or around the pushrod seal. Air in the system despite repeated bleeding.

Critical Brakes

Seized Rear Brake Cylinders

One rear wheel locks or drags. The car pulls to one side under braking. A burning smell from one rear wheel after driving.

Minor Body and Structure

Sill Corrosion (Inner and Outer)

The outer sill skin bubbles, softens, and eventually perforates. In advanced cases, the outer sill crumbles when prodded. The inner sill -- the structural member -- rots from inside the box section and loses its load-bearing capacity.

Critical Body and Structure

Floor Pan Corrosion

Soft or perforated floor pans, particularly in the footwells and under the seats. Wet carpet is a telltale sign. In severe cases, you can see the road through the floor.

Minor Body and Structure

A-Post Corrosion

Rust at the base of the windscreen pillars where they meet the scuttle panel. This area can be invisible until advanced.

Minor Body and Structure

Door Skin Corrosion

Rust along the bottom edge of each door, working upward from the inside.

All MGB GT problems