Engine code
M51 · 2,499 cc · turbocharged indirect-injection diesel inline-6 · 1991-2000 · 325td and 325tds, 525td and 525tds, 725tds
The M51 is BMW's 2.5 liter turbocharged six-cylinder diesel with indirect, swirl-chamber injection. Wikipedia says it was built at the Steyr plant from July 1991 to February 2000, replaced the M21 and was followed by the M57.
Not sold in US-market BMWs, per BMW's own vehicle lists (data to December 2019). Every M51 car in those lists belongs to the ECE (European-specification) or South African catalog, so this guide is a short one.
Quick read
- Ownership position: Not established yet. We are still researching this engine.
- Reliability: Not established yet. We are still researching this engine.
- Cost to own: Not established yet. We are still researching this engine.
- Power potential: Not established yet. We are still researching this engine. BMW's technical data gives the factory outputs in the At a Glance table.
- Main watch item: Not established yet. We are still researching this engine.
M51 At a Glance
| Question | Practical answer |
|---|---|
| Sold in the US | Not sold in US-market BMWs, per BMW's own vehicle lists (data to December 2019). Of 38 vehicle types listing the M51, 37 are in the ECE (European-specification) catalog and 1 is in the South African catalog. |
| Where you find it | E34 525td and 525tds, catalog dates 02/1990-06/1996; E36 325td and 325tds, catalog dates 01/1991-05/1999; E38 725tds, catalog dates 07/1995-02/2000; E39 525td and 525tds, catalog dates 04/1995-03/2000. These are catalog type dates, not production claims, in BMW's parts data, for sedans and Touring wagons. |
| Build window check | The parts data type records for the E34 and E36 start in 02/1990 and 01/1991, earlier than the July 1991 production start Wikipedia gives. The sources do not explain the gap. |
| Factory output | td in the E34 and E36: 85 kW at 4,800 rpm and 222 Nm at 1,900 rpm. tds in the E34 and E36: 105 kW at 4,800 rpm and 260 Nm at 2,200 rpm. tds in the E38 and E39: 105 kW at 4,600 rpm and 280 Nm at 2,200 rpm. All per BMW's technical data, which gives no separate figure for the E39 525td. |
| Reliability profile | Not established yet. We are still researching this engine. |
| Typical annual planning budget | Not established yet |
Technical Specifications
| Specification | Detail |
|---|---|
| Configuration | Inline-six turbocharged diesel. Wikipedia lists one chain-driven overhead camshaft, two valves per cylinder, a cast iron block and an aluminum head, indirect swirl-chamber injection fed by a Bosch VP37 distribution pump, and an intercooler on the tds versions. |
| Displacement | 2,499 cc in BMW's technical data, 80 mm bore x 82.8 mm stroke. Wikipedia gives 2,497 cc. The guide uses BMW's figure. |
| Compression ratio | 22:1 |
| Output by version | See "Factory output" above: td 85 kW (E34 and E36), tds 105 kW. |
| Engine management | Wikipedia lists Bosch DDE 2.1, later DDE 2.2. |
| Engine oil capacity | E34: 6.75 liters, 7.25 liters from 09/1995. E36: 6.5 liters, 7.0 liters from 09/1995. E38: 7.0 liters. E39: 6.75 liters. Per BMW's fluid data. |
| Engine oil grade, firing order, service part numbers | Not established |
Common Questions
What BMW models had the M51 engine?
BMW's parts data shows the M51 in the E34 525td and 525tds, E36 325td and 325tds, E38 725tds and E39 525td and 525tds.
Was the M51 sold in US-market BMWs?
No. Not sold in US-market BMWs, per BMW's own vehicle lists (data to December 2019). BMW's 2010 US press release on its diesels names the 524td, sold in the US for the 1985 and 1986 model years, and the 2009 US diesels, but no M51 car.
How much power did the M51 make?
BMW's technical data gives 85 kW for the td in the E34 and E36 and 105 kW for the tds, with torque from 222 Nm to 280 Nm depending on version and car.
What replaced the M51?
Wikipedia names the M57 as the M51's successor.
