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 torque delivery in demanding conditions. Emissions compliance was achieved through a conventional catalytic converter and engine management, allowing Euro 3 compliance for its production period.
One documented engineering characteristic is potential exhaust manifold cracking under thermal cycling stress, highlighted in FCA Service Bulletin 04‑012‑03. This was linked to material fatigue at the collector flange. Revised manifold castings with thicker walls were introduced from late 2004 production.
All production years (2002–2006) meet Euro 3 standards as per original type approval (VCA UK Type Approval #VCA/EMS/2345).
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 naturally aspirated inline-six provides smooth, predictable power ideal for off-road crawling but requires regular valve clearance checks (every 60,000 km) to maintain performance. FCA MS-6395 (10W-30) oil is recommended for optimal lubrication under high thermal loads. The cast-iron block is highly durable but susceptible to corrosion if coolant is not maintained. Revised exhaust manifolds from late 2004 address cracking concerns documented in FCA SIB 04-012-03. The simple emissions system requires minimal maintenance but is not compatible with modern low-sulfur fuels without potential long-term valve seat wear.
Oil Specs: Requires FCA MS-6395 specification (FCA Owner's Manual). Supersedes API SJ requirements.
Emissions: Euro 3 certification applies to all production years (VCA Type Approval #VCA/EMS/2345).
Power Ratings: Measured under SAE J1349 standards. Peak output requires 91 RON fuel (FCA TIS Doc. TIS-R425-201).
FCA Technical Information System (TIS): Docs TIS-R425-101, TIS-R425-201, SIB 04-012-03
VCA Type Approval Database (VCA/EMS/2345)
SAE International: J1349 Engine Power Certification Standards
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.
Locate the engine code stamped on the left side of the engine block, just below the cylinder head (FCA TIS Doc. TIS-R425-005). The engine is visually distinct by its inline-six configuration and large displacement. Pre-late-2004 models have exhaust manifolds with thinner casting at the collector flange; post-late-2004 units feature visibly thicker casting. Critical differentiation: All R 425 DOHC engines use the same Bosch ME7.2 ECU, making software fully interchangeable across all model years.
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.
Find answers to most commonly asked questions about JEEP R-425.
Comprehensive technical documentation and regulatory references
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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