Between 1997 and 2005, 4-cylinder Mercedes M166 engines with capacities ranging from 1.4 to 2.1 liters were manufactured. These engines were exclusively fitted to the compact A-class model and the Vaneo compact van, which was based on it. These units’ index was changed to M266 after they were upgraded to the next generation A-class.
M102, M111, M133, M139, M166, M200, M254, M260, M264, M266, M270, M271, M274, and M282 are the R4 Mercedes engines.
Specifications
| Production years | 1997-2005 |
| Displacement, cc | 1397 (M 166 E 14) 1598 (M 166 E 16) 1898 (M 166 E 19) 2084 (M 166 E 21) |
| Fuel system | injector |
| Power output, hp | 82 (M 166 E 14) 82 – 102 (M 166 E 16) 125 (M 166 E 19) 140 (M 166 E 21) |
| Torque output, Nm | 130 (M 166 E 14) 140 – 150 (M 166 E 16) 180 (M 166 E 19) 205 (M 166 E 21) |
| Cylinder block | aluminum R4 |
| Block head | aluminum 8v |
| Cylinder bore, mm | 80 (M 166 E 14) 80 (M 166 E 16) 84 (M 166 E 19) 84 (M 166 E 21) |
| Piston stroke, mm | 69.5 (M 166 E 14) 79.5 (M 166 E 16) 85.6 (M 166 E 19) 94 (M 166 E 21) |
| Compression ratio | 11.0 (M 166 E 14) 11.0 (M 166 E 16) 10.8 (M 166 E 19) 11.0 (M 166 E 21) |
| Features | SOHC |
| Hydraulic lifters | yes |
| Timing drive | chain |
| Phase regulator | no |
| Turbocharging | no |
| Recommended engine oil | 5W-40 |
| Engine oil capacity, liter | 4.5 |
| Fuel type | petrol |
| Euro standards | EURO 3/4 |
| Fuel consumption, L/100 km (for Mercedes A140 2001) — city — highway — combined |
9.7 5.6 7.1 |
| Engine lifespan, km | ~230 000 |
| Weight, kg | 95 |
The engine was installed on:
- Mercedes A-Class W168 in 1997 – 2004;
- Mercedes Vaneo W414 in 2001 – 2005.
Disadvantages of the Mercedes M166 engine
The engines had an unreliable ECU with an integrated flow meter during the early years of production.
Here, corrosion and quick wear of the camshaft journals and cams are also frequent.
The cabin smells like exhaust gases because the crankcase ventilation pipes are cracked.
A low resource sets the timing chain, generator, water pump, and oil pump apart.
Many operations are performed with the engine removed because of the unusual design.