1964 Hillman IMP 0.9L Petrol · RCA 633B

The Imp's all-aluminium 875cc Coventry Climax-derived engine relies on pristine coolant passages and strict inhibitor ratios to prevent electrolytic corrosion and hot spots. Neglected coolant changes, airlocks in the long cooling pipe runs, or water pump leaks cause rapid overheating. Because aluminium expands significantly when overheated, the cylinder head warps easily, crushing the head gasket, blowing fire-rings, and in severe cases pulling head studs from the alloy block threads.

Early Mark I Imps utilised an unconventional pneumatic throttle arrangement consisting of a rubber bellows displacer at the pedal connected via a small-bore nylon air pipe to an actuator diaphragm on the Solex carburettor. Over time, heat cycles perished the rubber bellows while cold winter temperatures caused the diaphragms to stiffen, split, or develop vacuum leaks. The car would suffer from erratic idle, delayed throttle response, or sudden total loss of accelerator control.

The rear suspension and transaxle on the Hillman Imp utilise flexible rubber Rotoflex couplings ('doughnuts') to absorb drivetrain shock and allow angular articulation of the rear driveshafts. Over time, exposure to gearbox oil leaks, exhaust heat, and road grime causes the reinforced rubber to dry out, fissure, and delaminate from its metal bolt inserts. Severe degradation leads to heavy driveline judder, clunking, and catastrophic detachment of the driveshaft.

The Imp's front semi-swing axle independent suspension employs traditional kingpins and bronze or nylon bushes inside the steering swivels. Because these swivels are exposed to road splash and frequently neglected during routine chassis greasing, grit ingress accelerates bush wear while old grease solidifies. Worn kingpins introduce steering vagueness, wander, uneven tyre shoulder wear, and direct MOT failure.