1966 Sunbeam Alpine 1.7L Petrol · MUL 479D

The unitary bodyshell of the Sunbeam Alpine relies on a multi-layer box sill assembly and an underfloor cruciform member for torsional stiffness. Water entering through neglected windscreen scuttles, blocked A-pillar drains, and rotten rear inner arches collects inside the sills and rear spring hanger boxes. On UK cars exposed to road salt and damp storage, internal rusting weakens the shell to the point where the chassis folds upward in the middle, causing the doors to jam against the B-posts. Repairing this structural decay requires extensive jigging and skilled fabrication of bespoke steel sections.

The Rootes four-cylinder engine features a cast-iron block topped with an aluminium alloy cylinder head. When historic owners failed to run adequate corrosion-inhibiting antifreeze, galvanic action set in between the dissimilar metals, eating away at the head faces around the water jacket passages. This internal electrolytic corrosion compromises the cylinder head gasket fire rings, resulting in compression loss, overheating, and oil-coolant cross-contamination. Severely eroded heads require specialist aluminium welding, skimming, and thread inserts, or replacement from scarce Rootes donor units.

Early Sunbeam Alpines used a crossflow radiator with a separate header tank, while Series III through V cars used a vertical-flow radiator. Over decades of classic storage and seasonal use, limescale, rust scale from the iron block, and cast-alloy oxide sludge accumulate in the narrow radiator core tubes. Restricted coolant circulation causes the engine temperature gauge to climb rapidly in slow-moving traffic or on motorway inclines. If ignored, the resulting thermal stress quickly triggers head gasket failure or head warping on the alloy top end.