Comprehensive service repair manual for the 1986-1992 Ford Sierra RS Cosworth covering all variants: three-door, Sapphire, 4x4, and RS500 evolution. Features detailed Cosworth YB 2.0L turbocharged engine overhaul, Garrett turbocharger rebuild procedures, Bosch K-Jetronic and Motronic fuel injection diagnosis, Borg-Warner T-5 transmission rebuild, Ferguson viscous 4WD system service, limited-slip differential adjustment, ventilated brake overhaul, boost control system diagnostics, wastegate testing, intercooler inspection, cooling system maintenance, RS suspension geometry, and electrical troubleshooting. Contains exploded views, OEM torque specifications, wiring diagrams, and diagnostic procedures essential for this iconic homologation special.
The Ford Sierra RS Cosworth stands as one of the most celebrated performance vehicles ever produced for the road, created to homologate a World Rally Championship contender. The heart of this machine is the forged-bottom-end Cosworth YB 2.0 liter turbocharged inline-four engine with Garrett turbocharger, dual overhead camshaft 16-valve aluminum head, and large-capacity intercooler producing 204 horsepower in standard Sierra RS Cosworth form and up to 224 horsepower in the legendary RS500 evolution variant. The Bosch K-Jetronic continuous fuel injection system on early models and Bosch Motronic digital management on later variants precisely meter fuel under the significant boost pressure of approximately 0.63 bar. Power transfers through a Borg-Warner T-5 five-speed manual transmission to a limited-slip differential. The 4x4 variant features a Ferguson viscous-coupling permanent four-wheel drive system with automatic torque distribution. Large ventilated disc brakes and RS-specific lowered suspension with uprated dampers complete the performance package.
VEHICLE EQUIPMENT INTRODUCTION:
Born from World Rally Championship homologation requirements, the Ford Sierra RS Cosworth combines Cosworth-engineered turbocharged performance with everyday road car practicality. The YB inline-four turbo engine, uprated suspension, and effective braking system made this the definitive performance sedan of the late 1980s with unmistakable aerodynamic styling.
SERVICE AND REPAIR SCOPE:
- Cosworth YB engine complete rebuild with block inspection and bore measurement
- Garrett turbocharger removal and cartridge rebuild with oil feed line service
- Bosch K-Jetronic and Motronic fuel injection diagnostics and adjustment
- Borg-Warner T-5 transmission overhaul with synchronizer ring replacement
- Ferguson 4WD viscous coupling service and fluid replacement (4x4 models)
- Limited-slip differential clutch pack inspection and preload adjustment
- Ventilated brake disc measurement and caliper piston rebuild
- RS suspension geometry with strut insert and spring replacement
- Wastegate actuator testing and boost pressure specification verification
- Intercooler inspection and charge pip boot integrity assessment
- Body panel alignment including distinctive rear wing mounting
- Twin radiator cooling system service and water pump replacement
- Electrical boost control circuit troubleshooting
- Exhaust downpipe and turbo gasket replacement
TECHNICAL SPECIFICATIONS:
- Engine: 1993cc Cosworth YB inline-4 DOHC 16-valve turbocharged
- Turbocharger: Garrett T3 with integrated exhaust manifold
- Boost pressure: 0.63 bar (9.2 psi) wastegate setting
- Horsepower: 204 stock, 220 Sapphire, 224 RS500
- Torque: 205-213 lb-ft at 3500 RPM
- Transmission: Borg-Warner T-5 5-speed manual
- Drivetrain: Rear-wheel drive or 4WD viscous coupling
- Compression ratio: 8.0:1
- Fuel system: Bosch K-Jetronic (early) or Motronic EFI (late)
- Brakes: 280mm front and 269mm rear ventilated discs
DIAGNOSTIC INFORMATION:
- Boost pressure testing across full RPM range with verification
- Fuel system enrichment analysis under boost conditions
- Intercooler charge air leak detection with smoke test procedure
- Wastegate diaphragm integrity test with hand vacuum pump
- Oil pressure verification at hot idle and sustained high RPM
- Cylinder compression test and leak-down specification
- Ignition timing base setting and boost retard function check
- Lambda sensor feedback verification for mixture control
- Engine knock sensor operation assessment under detonation threshold
ILLUSTRATIONS AND DIAGRAMS INCLUDED:
- Cosworth YB engine sectional view showing oil supply routing to turbo
- Turbocharger exploded assembly with cartridge bearing detail
- Bosch K-Jetronic fuel system component layout
- Ferguson 4WD drivetrain cross-section
- RS suspension geometry with alignment adjustment points
- Electrical circuit diagrams for engine management and boost control
- Exhaust routing from manifold through turbo to tailpipe
COMPATIBILITY:
- Covers: 1986 1987 1988 1989 1990 1991 1992 Ford Sierra RS Cosworth
- Models: Three-door hatchback, Sapphire saloon, 4x4, RS500 evolution
- All drivetrain and body configurations included
FILE PROPERTIES:
- Format: Searchable PDF
- Language: English
- Delivery: Instant digital download
- Access: Download anytime after purchase
The Ford Sierra RS Cosworth stands as one of the most celebrated performance vehicles ever produced for the road, created to homologate a World Rally Championship contender. The heart of this machine is the forged-bottom-end Cosworth YB 2.0 liter turbocharged inline-four engine with Garrett turbocharger, dual overhead camshaft 16-valve aluminum head, and large-capacity intercooler producing 204 horsepower in standard Sierra RS Cosworth form and up to 224 horsepower in the legendary RS500 evolution variant. The Bosch K-Jetronic continuous fuel injection system on early models and Bosch Motronic digital management on later variants precisely meter fuel under the significant boost pressure of approximately 0.63 bar. Power transfers through a Borg-Warner T-5 five-speed manual transmission to a limited-slip differential. The 4x4 variant features a Ferguson viscous-coupling permanent four-wheel drive system with automatic torque distribution. Large ventilated disc brakes and RS-specific lowered suspension with uprated dampers complete the performance package.
VEHICLE EQUIPMENT INTRODUCTION:
Born from World Rally Championship homologation requirements, the Ford Sierra RS Cosworth combines Cosworth-engineered turbocharged performance with everyday road car practicality. The YB inline-four turbo engine, uprated suspension, and effective braking system made this the definitive performance sedan of the late 1980s with unmistakable aerodynamic styling.
SERVICE AND REPAIR SCOPE:
- Cosworth YB engine complete rebuild with block inspection and bore measurement
- Garrett turbocharger removal and cartridge rebuild with oil feed line service
- Bosch K-Jetronic and Motronic fuel injection diagnostics and adjustment
- Borg-Warner T-5 transmission overhaul with synchronizer ring replacement
- Ferguson 4WD viscous coupling service and fluid replacement (4x4 models)
- Limited-slip differential clutch pack inspection and preload adjustment
- Ventilated brake disc measurement and caliper piston rebuild
- RS suspension geometry with strut insert and spring replacement
- Wastegate actuator testing and boost pressure specification verification
- Intercooler inspection and charge pip boot integrity assessment
- Body panel alignment including distinctive rear wing mounting
- Twin radiator cooling system service and water pump replacement
- Electrical boost control circuit troubleshooting
- Exhaust downpipe and turbo gasket replacement
TECHNICAL SPECIFICATIONS:
- Engine: 1993cc Cosworth YB inline-4 DOHC 16-valve turbocharged
- Turbocharger: Garrett T3 with integrated exhaust manifold
- Boost pressure: 0.63 bar (9.2 psi) wastegate setting
- Horsepower: 204 stock, 220 Sapphire, 224 RS500
- Torque: 205-213 lb-ft at 3500 RPM
- Transmission: Borg-Warner T-5 5-speed manual
- Drivetrain: Rear-wheel drive or 4WD viscous coupling
- Compression ratio: 8.0:1
- Fuel system: Bosch K-Jetronic (early) or Motronic EFI (late)
- Brakes: 280mm front and 269mm rear ventilated discs
DIAGNOSTIC INFORMATION:
- Boost pressure testing across full RPM range with verification
- Fuel system enrichment analysis under boost conditions
- Intercooler charge air leak detection with smoke test procedure
- Wastegate diaphragm integrity test with hand vacuum pump
- Oil pressure verification at hot idle and sustained high RPM
- Cylinder compression test and leak-down specification
- Ignition timing base setting and boost retard function check
- Lambda sensor feedback verification for mixture control
- Engine knock sensor operation assessment under detonation threshold
ILLUSTRATIONS AND DIAGRAMS INCLUDED:
- Cosworth YB engine sectional view showing oil supply routing to turbo
- Turbocharger exploded assembly with cartridge bearing detail
- Bosch K-Jetronic fuel system component layout
- Ferguson 4WD drivetrain cross-section
- RS suspension geometry with alignment adjustment points
- Electrical circuit diagrams for engine management and boost control
- Exhaust routing from manifold through turbo to tailpipe
COMPATIBILITY:
- Covers: 1986 1987 1988 1989 1990 1991 1992 Ford Sierra RS Cosworth
- Models: Three-door hatchback, Sapphire saloon, 4x4, RS500 evolution
- All drivetrain and body configurations included
FILE PROPERTIES:
- Format: Searchable PDF
- Language: English
- Delivery: Instant digital download
- Access: Download anytime after purchase
