INTRODUCTION

Never mind the Audi quattro; for anyone born east of Bow Bells it’s the Sierra ‘Cossie’ that defined the 1980s, often finished in a white as brilliant as the socks of the youths who lusted after them. Now those youths have grown up, prices have matured alongside them and the best ones are worth as much as – or more than – contemporary Ferraris.

The Sierra RS Cosworth resulted from a chance conversation about Ford’s poor results in touring car racing. In 1983, motor sport boss Stuart Turner suggested mating an experimental Cosworth 16-valve engine with a turbocharger and inserting it in a three-door Sierra shell. The roadgoing Sierra RS Cosworth debuted in 1985.

Wind tunnel tests resulted in the car’s signature whale-tail spoiler, which made the car stable at racing speeds, although laggy power delivery and a simple chassis gave tail-happy cornering.

The ‘Cossie’ evolved further into the RS500, built to homologate a bigger turbo and keep the racing version ahead of rivals; and the subsequent, more subtle-looking four-door Sapphire that, in its final iteration, gained four-wheel drive.

Finding an unmolested car is a serious challenge and, because of some dubious rustproofing, finding one in sound condition is harder still. But it’s worth it, especially for the three-door models, which seem set to follow the RS500’s sharp climb in values.

MARKET VIEW

Primitive security measures and a rampant market in secondhand spares meant a great many were stolen and broken up, which still occasionally happens. This thinning of the flock, combined with the rear-wheel-drive Sapphire’s drop in value through the 1990s that left many thrashed or crashed, has meant the three-doors and RWD Sapphires are now scarce.

‘I think the DVLA records show about 400-500 three-doors on the road in the UK,’ says Karl Norris (above) of Cosworth specialist Norris Motorsport, ‘and of those only a few dozen will be in nice condition. It’s dangerously easy to buy a pig.’

Prices range from £7000 to £15,000 (more for the very best), with RWD Sapphires seen as a cheaper substitute at £5000-£12,000. The four-wheel-drive version rarely gets above £7000, starting at £4500 for one you’d consider. RS500s have shot up and will energise the market for the other three-doors: most are between £20,000 and £40,000.

IN A NUTSHELL

The greatest rust concerns are reserved for the three-doors. ‘They rot badly around the front suspension turrets,’ says Karl. ‘The top of the strut can eventually fall inwards, and they’ll also rust where the inner wing meets the bulkhead. That’s even more serious, as the front of the car collapses.’ How to spot it? ‘Look for a narrowing of the gap between the door and the front wing.’

Sills and floors need inspection on both models, as do the rear chassis legs near the spring seats. The Sapphire avoids the front-end rot, but the rear wheelarch area is notoriously rust-prone.

As with everything that bolts on, be sure the running gear is to original specification. Many cars have been lowered, which together with wheels larger than the standard 7.0J 15in alloys can harm an already firm ride. In 4x4 models, lowering accelerates CV joint wear – listen for a clicking as you turn on full lock. Gearboxes with worn synchromesh on second and third can be a bargaining point. All rear-drive versions used a viscous coupling LSD, which can be repacked if you’re getting lots of wheelspin on your test drive.

A later engine in an early car is a good thing if you’re not after an investment-grade original because all rear-wheel-drive cars used a head design that led to water leaks from failed head gaskets (£650 + VAT to correct with a skim and pressure test): look on the exhaust side of the block for drips.

Engines got steadily better: find the number on the head next to the exhaust cam pulley. They started near zero, rising beyond 13,000 in the rear-drive Sapphires. Any three-door showing a number in the hundreds needs extra caution. Many rear-drive cars suffer piston slap: a growling sound from the engine on cold start-up. It shouldn’t be there if revved when warm.

‘Check the turbo by removing the front hose and prodding the impeller,’ says Karl. ‘Any front-to-rear movement means it hasn’t got long left.’

Modifications are a minefield; avoid anything without printed history from a specialist. But as long as the TO3 turbo and factory intercooler remain, other ‘upgrades’ won’t overstress the engine and the car can almost be considered standard.
 
Two electrical issues need attention: fuel pump wiring was marginal and the voltage drop between battery and fuel tank can leave the mixture dangerously lean at full boost. See if it’s been rewired. ‘Older alarms and immobilisers are often a nightmare,’ says Karl. Be doubly sure everything works as it should, consistently.

CONCLUSION

RS500s are firmly in collector territory, and well-preserved three-doors look set to follow them into the climate-controlled garage. This is a shame, as they’re all an outrageous adrenaline kick to drive, while providing a belt of 1980s nostalgia from the lairy looks and sporty, low-rent Ford interior. That makes the Sapphires (especially the 4x4) excellent value, offering every chance of appreciation with subtler looks. All get by on family-hatch service costs: Karl Norris suggests £180 for a minor service and only £600 for that plus the major belt-change they need every 30,000 miles or five years. Get in now before the last decent, affordable examples vanish.