How much does an M104 engine replacement cost?

A reconditioned M104 typically costs £2,400–£3,800 supply only, varying by displacement and specific variant. Fitting adds £900–£1,300 depending on labour rates. Use our calculator for a figure specific to your car.

Is the Mercedes M104 a reliable engine?

The M104 is rated 3.5★ out of 5 — it is widely regarded as one of Mercedes' best straight-six engines, with a characterful, smooth power delivery and strong durability. However, the biodegradable wiring harness and head gasket issues are well-documented weak points that require attention.

What is the most common M104 failure?

The most common issues are biodegradable wiring harness failure (the insulation degrades, causing electrical faults) and head gasket failure (especially on 3.2-litre variants). Camshaft wear and coil pack failures are also reported on higher-mileage examples.

Which Mercedes models use the M104?

The M104 powered a wide range of Mercedes models including the E-Class (W124/W210), S-Class (W140), SL-Class (R129), C-Class (W202), CLK-Class (C208), and G-Class (W463), across 2.8-litre and 3.2-litre displacements.

How long does the M104 last?

With proper maintenance — including wiring harness replacement if original and head gasket monitoring — the M104 is capable of 200,000+ miles. Many examples remain on UK roads today, testament to its fundamental engineering quality.

Mercedes-BenzM104PetrolStraight-Six1989–1999

Mercedes-Benz M104 Engine – Specs, Reliability & Replacement Cost

The Mercedes M104 is a 2.8–3.2-litre straight-six – one of Mercedes' most revered petrol engines, but its wiring harness and head gasket are known weak points. Backed by real UK enquiries from EnginesMarket.co.uk.

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Mercedes-Benz M104 Engine – Specs, Reliability & Replacement Cost

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Enquiry Data Available
15+
Models
Fitted
78/100
Engine
Score
Part of Engine Finders

Jaguar Mercedes-Benz M104 Engine Overview

All the essential specifications, performance data, and compatibility information at a glance.

Engine Family

Mercedes-Benz M104

Fuel

Petrol

Power Range

190–276 hp

Overall Engine Score

78/100

★★★★☆

Configuration / Displacement

Inline-6, 2.8L–3.2L

Modern turbodiesel four-cylinder engine with proven architecture.

Years Produced

1989–1999

Over a decade of production and continuous development.

Models Fitted (BMW only)

Fitted across a wide range of BMW vehicles and body styles.

Cross-Brand Fitment

Exclusive to Mercedes-Benz

The N47 engine is engineered exclusively for BMW vehicles.

BMW-Verified Data

Verified using real UK enquiries and workshop data.

Real-World Insights

Based on 1,450+ UK enquiries in 2025.

Trusted by Enthusiasts

Part of Engine Finders - UK's leading engine specialists.

Quality You Can Trust

Every engine is checked, inspected and quality assured.

Engine Family

Mercedes-Benz M104

Fuel

Petrol

Configuration /
Displacement

Inline-6, 2.8L–3.2L

Power Range

190–276 hp

Years Produced

1989–1999

Models Fitted (BMW only)

Cross-Brand Fitment

Exclusive to Mercedes-Benz

Overall Engine Score

78/100

★★★★☆

Verdict & Rating

Rating:

3.5

out of 5

82% confidence – based on verified specialist rebuild reports and UK workshop consensus.

The M104 is a smooth, characterful straight-six and a modern classic – but biodegradable wiring harnesses and head gaskets are its defining weaknesses – budget for preventative replacement or restoration.

Best for:

Enthusiasts wanting a classic Mercedes straight-six experience with strong performance.

Avoid if:

You're not prepared for classic-car maintenance costs or wiring harness replacement.

Engine Score breakdown:

DimensionScore (of 20)

Reliability

3.5★ × 4

14 /20

Repair Cost

Reconditioned supply midpoint £3,000–£4,999

16 /20

Repairability

Mix of cheap fixes (gaskets, sensors) and expensive ones (head gasket, wiring harness)

12 /20

Parts Supply

Available but dealer/specialist-order only; some parts becoming scarce

16 /20

Replacement Economics

Recon cost 30–44% of lowest host-vehicle value

20 /20

Total Engine Score

78 / 100

Rating:

3.5

out of 5

82% confidence – based on verified specialist rebuild reports and UK workshop consensus.

The M104 is a smooth, characterful straight-six and a modern classic – but biodegradable wiring harnesses and head gaskets are its defining weaknesses – budget for preventative replacement or restoration.

Engine Score breakdown:

DimensionScore (of 20)

Reliability

3.5★ × 4

14 /20

Repair Cost

Reconditioned supply midpoint £3,000–£4,999

16 /20

Repairability

Mix of cheap fixes (gaskets, sensors) and expensive ones (head gasket, wiring harness)

12 /20

Parts Supply

Available but dealer/specialist-order only; some parts becoming scarce

16 /20

Replacement Economics

Recon cost 30–44% of lowest host-vehicle value

20 /20

Total Engine Score

78 / 100

Best for:

Enthusiasts wanting a classic Mercedes straight-six experience with strong performance.

Avoid if:

You're not prepared for classic-car maintenance costs or wiring harness replacement.

Compatible Jaguar Models

Jaguar Engine engines are fitted across 7+ models from 1989–1998.

Jaguar Exclusive Engine

This is an exclusive Jaguar engine. No cross-platform sharing.

1989

9 Years of Production

1998

E-Class

W124 · W210

E 280 / E 320 (M104.942/M104.992) · E 320 Cabriolet / Coupe · E 280 / E 320 (M104.941/M104.995)

1992–19973 Variants →

S-Class

W140

S 280 / S 320 (M104.944/M104.945)

1991–19981 Variants →

SL-Class

R129

SL 280 / SL 320 (M104.943/M104.991)

1989–19981 Variants →

C-Class

W202

C 280 (M104.941)

1993–19971 Variants →

CLK-Class

C208

CLK 320 (M104.995)

1997–19981 Variants →

G-Class

W463

G 320 (M104.996)

1994–19971 Variants →

S-Class

Coupe

C140

CL 320 / CL 420 (M104.945)

1992–19981 Variants →

+

Other Jaguar Models

Engine also appears in limited variants and markets.

View full details →

Compatibility Verified

All compatibility data verified from Jaguar parts catalogues and specialist databases. [JAGUAR-VERIFIED]

E-Class

Generation

W124

Variant/Badge

E 280 / E 320 (M104.942/M104.992)

Years

1992–1995

E-Class

Generation

W124

Variant/Badge

E 320 Cabriolet / Coupe

Years

1993–1997

S-Class

Generation

W140

Variant/Badge

S 280 / S 320 (M104.944/M104.945)

Years

1991–1998

SL-Class

Generation

R129

Variant/Badge

SL 280 / SL 320 (M104.943/M104.991)

Years

1989–1998

C-Class

Generation

W202

Variant/Badge

C 280 (M104.941)

Years

1993–1997

E-Class

Generation

W210

Variant/Badge

E 280 / E 320 (M104.941/M104.995)

Years

1995–1997

CLK-Class

Generation

C208

Variant/Badge

CLK 320 (M104.995)

Years

1997–1998

G-Class

Generation

W463

Variant/Badge

G 320 (M104.996)

Years

1994–1997

S-Class

Coupe

Generation

C140

Variant/Badge

CL 320 / CL 420 (M104.945)

Years

1992–1998

+

Other Jaguar Models

Engine also appears in limited variants and markets.

View full details ›

Compatibility Verified

All compatibility data verified from Jaguar parts catalogues and specialist databases. [JAGUAR-VERIFIED]

(Exclusive mode – no cross-link)

Jaguar Engine Engine Price Guide

All prices are estimates from UK specialists [JAGUAR-QUOTE]

i

Fitting an M104 typically takes 10–14 hours at £65–£95/hr (independent) or £110–£160/hr (London/SE dealer).

(Exclusive mode – no cross-link)

USED

Supply Only

£600–£1,500

Fitted (Indie)

£1,100–£2,200

3–6 months

Jaguar Engine Engine Price Guide

All prices are estimates from UK specialists

[JAGUAR-QUOTE]

USED

Supply Only

£600–£1,500

Fitted (Indie)

£1,100–£2,200

Warranty

3–6 months

Frequently Asked Questions

Expert answers to the most common BMW Engine engine questions.

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