1973 Triumph Stag

The bespoke 3.0-litre Triumph V8 suffered notorious overheating due to a high-mounted water pump that easily air-locked if coolant dropped, narrow engine water passages, and casting sand left in blocks from the factory. Furthermore, cylinder head studs entered the block at two opposing angles, producing lateral stress when hot that readily warped the aluminium heads and breached head gaskets.

Symptoms: Temperature gauge needle creeping into the hot zone during idle or slow urban traffic, Combustion bubbles visible in the cooling expansion tank or coolant overflow bottle...

Est. repair cost: £1,200–£3,500

The Triumph 3.0-litre V8 uses long single-row duplex chains to drive each overhead camshaft from a jackshaft. The timing chains stretch with use, and hydraulic tensioners wear or fail when oil changes are neglected or oil pressure drops. A stretched chain causes severe valve timing deviation, can jump teeth on sprockets, or snap completely, causing catastrophic piston-to-valve collision in the interference engine.

Symptoms: Distinct metallic rattling or clattering noise from the front timing cover on cold start, Uneven or lumpy idle accompanied by loss of crisp low-end engine acceleration...

Est. repair cost: £800–£2,000

Constructed from untreated 1970s British Leyland steel with complex multi-box sections, the Stag body is highly prone to structural tinworm. Water leaks through weathered targa and windscreen seals soak into cabin carpets, rotting out inner and outer sills, floorpans and the crucial A-pillars behind front trim panels. Corroded sills cause the open body tub to flex and sag, misaligning doors and weakening the roll hoop structure.

Symptoms: Doors dropping on their latches or catching against B-posts when opening and closing, Visible blistering, bubbling paint and pinholes along outer sill seams and wheel arches...

Est. repair cost: £1,500–£5,000

The independent rear suspension uses semi-trailing arms with rubber bushes that degrade and soften with age, causing wayward rear geometry and excessive rear-wheel steer under throttle changes. Furthermore, the sliding splines on the rear half-shafts require regular greasing; when neglected, torque forces cause the splines to bind under acceleration and cornering, producing violent chassis lurches.

Symptoms: Vague, wandering rear handling or sudden twitching over bumps and mid-corner throttle changes, Noticeable metallic clunking or thumping from the rear axle when pulling away from rest...

Est. repair cost: £350–£900