SIERRA RS COSWORTH THREE-DOOR
The original Sierra RS Cosworth three-door is ultra-cool, immensely tuneable and extremely desirable. Here’s how to buy a bank-beating investment that’s equally able to annihilate your wallet…
IDENTITY
Cosworths were crowned king of the 1990s’ cartheft pandemic, and even today it’s vital to ensure any three-door hasn’t been stolen, written off or had its identity changed. A history check is essential, and if it doesn’t add up, steer well clear.
Compare the chassis number on the logbook with the number on the VIN plate riveted to the slam panel and beneath a flap in the carpet beside the driver’s seat; it should read WF0EXXGBBE, followed by a series of two letters and five digits; these last seven characters should match the original engine number. Beware of missing stamps, although several Sierras have been welded over due to rotten inner sills. Any groundoff or home-stamped number is a special code that translates as ‘run away.’
A YBB’s engine number is on a flat section near the offside engine mount, with another handstamped by Cosworth on the front of the block next to the water pump, behind the cambelt cover; it will begin with YBB, followed by several numbers. Other digits on the VIN plate should read N5 for
engine, B (right-hand drive) for drive, J for trans, 3 for axle, S2 for trim, and BEF in the type box.
Fakes, ringers and replicas are out there, worth considerably less than genuine Cosworths. A real UK three-door Cosworth road car will have a factory-fitted sunroof, tinted glass (check for an etched registration number), electric front windows, bigger gearbox tunnel (compared with a base-model three-door Sierra shell), straight (horizontal) towing eye, and factory-pressed cutout behind the ABS pump.
INTERIOR
A mint interior adds thousands to the a three-door’s price – and a ropey cabin subtracts as much.
Dashboards are renowned for warping and splitting, and good replacements cost more than £1000. Repairs are possible, although most don’t tend to last long. Some cars have been fitted with uncracked Sapphire dashboards (which lack the speaker grille in the top of the genuine three-door dash), with appropriate reduction in value.
Sierra door cards are similarly rare and pricey, suffering from the vinyl wrinkling up and peeling off, or being hacked to house speakers.
Factory-fitted Recaro front seats are becoming hard to find in excellent condition, so – yes, you guessed it – they’re stupidly expensive. Check for tatty bolsters, sagging cloth, and sloppy reclining mechanisms. Make sure the driver’s side hasn’t been swapped for a passenger seat, which has the recliner knob next to the centre console instead of the proper position beside the door.
Sierra headlinings are prone to sagging (and can be repaired relatively cheaply), as are rear parcel shelves (which cost a bomb); a Cosworth should have a single-piece shelf with a plastic storage box (designed for a non-standard first aid kit).
Don’t be surprised to find sticky electric windows or central locking motors, a non-working heater blower, or random bulbs alight on the dashboardmounted graphic information display; most parts are cheap enough to fix.
Use the cabin to judge the rest of the car. Cosworth trim is relatively hardy, so if you see a supposedly-low-mileage Sierra with tatty steering wheel and worn pedal rubbers, suspect it’s been around the clock.
ENGINE
Cosworth YB powerplant is the stuff of legends. It’s also the creator of nightmares if things go wrong. And they certainly do.
Original three-doors had a YBB engine. Early versions were weakest, but all should have been repaired or rebuilt by now. Listen for piston slap from cold: if it still sounds like a diesel when warm, account for a rebuild. Tired YBs tend to growl and knock, suggesting crankshaft/bearing/bore wear and big bills; all parts are available, but it’s an expensive business.
Head gasket failure can be equally walletworrying – especially if it damages the cylinder head. Check for coolant dripping down the cylinder block on the exhaust side, water in the oil, or white clouds exiting the exhaust.
Black smoke is normal for a tuned engine (running rich), but beware of blue plumes of oil smoke: odd puffs at idle are common, but heavy smoke under throttle could be worn piston rings or a blown turbo; check it for play by removing the intake hose and wiggling the compressor wheel.
Misfires are a familiar factor of Cosworth ownership – sometimes serious (such as a blown head gasket) but usually symptomatic of an aged electrical or ignition system. Cossies are renowned for eating spark plugs, leads and coil, and many issues are cured with a wasted spark conversion – but that detracts from originality and value. Boost problems may be due to split or loose hoses, sensors and regulators. Swapping paper gaskets for Cometic type is useful (especially at the inlet manifold), while a replacement engine loom can work wonders.
Check the existing wiring for corroded, chafed or bodged-together cables and connectors, especially in the engine bay beneath the nearside bonnet vent. Make sure the cooling fans cut in when the engine’s hot (the wiring is prone to melting), and inspect the fuel pump, filter and cradle (beneath the boot floor). Test the pump is receiving 13 volts, and if the cradle is caked in rust, anticipate problems.
Old three-door ECUs (Level 1/L1) can also be problematic, generally supplanted by a Sapphire’s L6. A cheeky Stage 1 chip wakes up a Cossie, and shouldn’t detract from the car’s value.