The 2.5-liter BMW M51 diesel engine was assembled at a plant in Austria from 1991 to 2001 and installed on such popular models as the 3-Series in the E36 body and the 5-Series in the E34 and E39 bodies. This power unit was upgraded in 1996 and received a new M51TU index.
The engine was installed on:
- BMW 3-Series E36 in 1991 – 1999;
- BMW 5-Series E34 in 1991 – 1996; 5-Series E39 in 1996 – 2000;
- BMW 7-Series E38 in 1996 – 2000;
- Opel Omega B (V94) in 1994 – 2001;
- Land Rover Range Rover 2 (P38A) in 1994 – 2002.
Specifications
| Production years | 1991-2001 |
| Displacement, cc | 2497 |
| Fuel system | vortex chamber |
| Power output, hp | 115 (M51D25 UL) 143 (M51D25 OL) 115 (M51D25TU UL) 143 (M51D25TU OL) |
| Torque output, Nm | 222 (M51 UL) 260 (M51 OL) 230 (M51TU UL) 280 (M51TU OL) |
| Cylinder block | cast iron R6 |
| Block head | aluminum 12v |
| Cylinder bore, mm | 80 |
| Piston stroke, mm | 82.8 |
| Compression ratio | 22.0 |
| Features | no (M51 UL) intercooler (M51 OL) no (M51TU UL) intercooler (M51TU OL) |
| Hydraulic lifters | yes |
| Timing drive | chain |
| Phase regulator | no |
| Turbocharging | MHI TD04-11G-5 (M51 UL) MHI TD04-11G-5 (M51 OL) Garrett TB2514 (M51TU UL) MHI TD04-13T-4 (M51TU OL) |
| Recommended engine oil | 5W-40 |
| Engine oil capacity, liter | 6.5 (M51 UL, M51 OL) 7.0 (M51TU UL, M51TU OL) |
| Fuel type | diesel |
| Euro standards | EURO 1/2 (M51 UL, M51 OL) EURO 2/3 (M51TU UL, M51TU OL) |
| Fuel consumption, L/100 km (for BMW 525tds 1994) — city — highway — combined |
11.3 6.1 8.0 |
| Engine lifespan, km | ~350 000 |
Disadvantages of the M51D25 engine
- The main problem with this diesel engine is cylinder head cracking due to overheating;
- Still here, the valve timing is often lost as a result of stretching the timing chain;
- Poor-quality or old oil quickly affects the condition of the high-pressure fuel pump plunger pair;
- Difficult start of a cold engine hints at the failure of the booster pump;
- On runs over 150,000 kilometers, the turbocharger often already requires replacement.
