The Jeep R 425 DOHC is a 4,250 cc, inline‑six naturally aspirated petrol engine produced between 2002 and 2006. It features sequential multi‑port fuel injection, dual overhead camshafts (DOHC), and a cast‑iron block with aluminum head, delivering 147 kW (200 PS) and 339 Nm of torque. Its robust architecture prioritizes low‑end pulling power for off‑road capability.
Fitted exclusively to the TJ Wrangler, the R 425 DOHC was engineered for rugged durability and smooth tor…
All production years (2002–2006) meet Euro 3 standards as per original type approval .
The Jeep R 425 DOHC is a 4,250 cc inline‑six naturally aspirated petrol engineered for the TJ Wrangler (2002-2006). It combines sequential multi-port injection with dual overhead camshafts to deliver smooth, linear power and strong low-end torque ideal for off-road use. Designed to meet Euro 3 standards, it prioritizes mechanical simplicity and durability.
| Parameter | Value | Source |
|---|---|---|
Displacement | 4,250 cc | |
Fuel type | Petrol | |
Configuration | Inline‑6, DOHC, 24‑valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 96.0 mm × 98.0 mm | |
Power output | 147 kW (200 PS) @ 4,600 rpm | |
Torque | 339 Nm @ 3,200 rpm | |
Fuel system | Sequential multi-port fuel injection | |
Emissions standard | Euro 3 | |
Compression ratio | 9.3:1 | |
Cooling system | Water‑cooled | |
Turbocharger | None | |
Timing system | Chain‑driven | |
Oil type | FCA MS-6395 (SAE 10W‑30) | |
Dry weight | 220 kg |
The Jeep R 425 DOHC was used exclusively in the Jeep TJ Wrangler platform with longitudinal mounting. This engine received no significant platform-specific adaptations beyond standard TJ mounting points. All models from 2002-2006 are mechanically compatible, though late-2004+ units feature the revised exhaust manifold. All adaptations are documented in OEM technical bulletins.
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The R 425 DOHC engine's primary reliability consideration is exhaust manifold cracking under repeated thermal cycling, with elevated incidence in high-mileage or frequently off-road driven vehicles. FCA internal quality reports from 2004 noted a measurable rate of manifold failure in pre-late-2004 builds, while owner feedback frequently cites oil leaks from the valve cover gasket. Consistent use of correct oil specification and coolant maintenance makes preventative upkeep critical.
Analysis derived from FCA technical bulletins (2003-2006) and owner-reported failure data (2005-2024). Repair procedures should follow manufacturer guidelines.
The most common questions about engine codes, what they mean, how to find them and how this database works
The R 425 DOHC is renowned for its exceptional long-term durability and simplicity. The main documented issue is exhaust manifold cracking on pre-late-2004 models, addressed with a revised part. With regular oil changes, coolant maintenance, and timely replacement of wear items like the water pump and sensors, this engine can easily exceed 300,000 km.
The most common issues are exhaust manifold cracking (pre-late-2004), valve cover gasket leaks, water pump failure, and crankshaft position sensor faults. These are well-documented in FCA service bulletins and are generally inexpensive and straightforward to repair.
The 4.0L R 425 DOHC inline-six petrol engine was used exclusively in the Jeep Wrangler (TJ) from 2002 to 2006. It was the standard and only engine option for the TJ during this period, replacing the previous 4.0L SOHC engine.
Yes, but gains are modest due to its naturally aspirated design. Common modifications include a cold air intake, performance exhaust, and ECU remapping, which can yield 10-15 kW extra. Forced induction (turbo/supercharger) kits exist but require significant supporting modifications and are not recommended for daily drivers.
Fuel economy is modest due to the engine's size and the Wrangler's weight and aerodynamics. Expect around 14.5 L/100km (19 mpg UK) in city driving and 10.5 L/100km (27 mpg UK) on the highway. Real-world combined figures typically range from 12-13 L/100km (22-24 mpg UK).
No. The R 425 DOHC is a non-interference engine. If the timing chain fails or jumps, the pistons will not contact the valves, preventing catastrophic internal damage. This is a key factor in its legendary reliability.
FCA recommends oil meeting specification MS-6395, typically a 10W-30 mineral or semi-synthetic. This oil provides the necessary film strength for the flat-tappet camshaft design. Change intervals should not exceed 10,000 km or 6 months for optimal engine longevity.
Comprehensive technical documentation and regulatory references
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Regulatory Stability
EU regulations are referenced using CELEX identifiers for long-term stability.
EUR-Lex
EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
UK type-approval authority for automotive products.
Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
WLTP and RDE testing procedures for emissions certification.
GOV.UK: Vehicle Approval
UK compliance and certification requirements for imported and modified vehicles.
VCA Certification Portal
Type-approval guidance and documentation.
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