Reconditioned Mercedes Sprinter Engine

Reliable day-to-day, vulnerable under the cylinder head: what the OM602, OM611, OM646 and OM651 reveal

The Mercedes Sprinter has spanned three engine generations between 2000 and 2018, each with its own specific weak points. The OM602 (code 602980), a 2.9 l inline 5-cylinder, is the oldest of the range: robust under heavy use, its main vulnerabilities are head gasket failure and ageing injection pumps. The OM611 (codes 611987, 612981), the first-generation 2.2 CDI, introduced common rail injection to the Sprinter — and with it came the turbo and high-pressure rail problems typical of early Mercedes CDI units. The OM646 (codes 646984, 646985, 646986), the second-generation 2.2 CDI and 2.1 CDI, is the most widespread engine in the range: its well-known Achilles heel is cylinder head cracking, accelerated by the repeated thermal cycles endured by high-mileage vans. The OM651 (code 651955), 2.1 CDI, rounds off the range with a timing chain design known to be prone to tensioner and oil pump issues on early examples.

Four engine families, four identification approaches

A 2.2 CDI Sprinter can be fitted with either an OM611 or an OM646 depending on the year of manufacture — two blocks that share no structural components whatsoever. The engine code stamped on the block is the only reliable way to remove any doubt: going by engine capacity or the horsepower figure alone is not sufficient. Codes 646984, 646985 and 646986 correspond to different power variants of the same OM646 and are not mechanically interchangeable without prior verification. For the OM651, the situation is the same: the code 651955 is essential to confirm exact compatibility.

Available reconditioning options

The engines in this range are available on an exchange basis or as a rebuild of the customer's own unit, subject to available references. All are supplied as a bare engine: ancillaries, turbo, alternator and starter motor are not included and must be refitted from the original unit.