Miniature of a Head Gasket for BMW M51

Keychain – Head Gasket for BMW M21 2.4 Diesel

The BMW M21 is the engine that marked BMW’s entry into series-production diesel cars during the 1980s. The 2,443 cc inline-six first appeared in the BMW 524td E28 in 1983 and was later used in the naturally aspirated 524d, the E30 324d and 324td, and the E34 524td. BMW produced the M21 both as an 86 PS naturally aspirated diesel and as a 115 PS turbo diesel. That combination was unusual for its era: BMW paired the brand’s familiar straight-six layout with a diesel concept intended not only to reduce fuel consumption but, particularly in the 524td, to deliver comparatively strong performance as well.

Technically, the engine is designated M21D24. It has 2,443 cc displacement, an 80 mm bore and 81 mm stroke, a single overhead camshaft and two valves per cylinder. Fuel is supplied through indirect swirl-chamber diesel injection. The basic engine was developed from BMW’s M20 petrol-engine architecture but extensively adapted for diesel operation. Early turbo versions still used mechanically controlled injection, while the E30 324td introduced BMW’s electronically controlled Digital Diesel Electronics system. A smaller turbocharger was also fitted to improve response. The later E34 524td continued with electronically controlled diesel injection.

The differences between the individual versions matter to owners. The E30 324d and E28 524d are naturally aspirated and produce 63 kW or 86 PS with 152 Nm. The 324td and 524td produce 85 kW or 115 PS; early turbo versions deliver 210 Nm, while later electronically controlled engines reach 220 Nm. Today, maintenance and restoration discussions typically involve the cooling system, timing belt, injection pump, injectors and, on TD models, the turbocharger. With an indirect-injection diesel of this age, overall condition, service history and decades of thermal use usually matter more than broad statements about the engine family’s durability.

Among BMW enthusiasts, the M21 is mainly associated with the E28, E30 and E34. The E28 524td was BMW’s first production diesel model and was positioned at launch as an unusually fast turbo diesel. The smaller E30 subsequently offered both the economical 324d and the turbocharged 324td, with the latter also available as a Touring. The E34 524td carried the engine family into the early 1990s before the newer M51 generation replaced it. Outside BMW, the M21 also appeared in vehicles including the Lincoln Continental and Continental Mark VII, Bertone Freeclimber and rare Vixen 21 TD. Identification codes such as 246D, 246DA, 246TA and 246TB are therefore also associated with this engine family.

Whether it lives on your own keys or as a gift for someone with a 324d, 324td or 524td, this keychain refers specifically to BMW’s first major diesel generation. Anyone familiar with M21D24, an E30 324td or an E28 524td will recognise the connection immediately. Today, the M21 is interesting less for outright performance than for its place in BMW history and its distinctive straight-six character for a diesel engine of its period.

Proudly crafted in Germany, meticulously detailed and finely finished for a refined in-hand feel paired with a premium brushed surface.