40 years is a long time in the automotive world. While a few prized cars from the 1980s may explode in value, not many people will consider their 40-year-old engine technology reliable. However, one diesel engine has stood the test of time: the Cummins B-series. Rudolf Diesel invented the diesel engine in 1897, but Clessie Cummins – and his Cummins Engine Company – would continue to refine the technology through a long list of patents and diesel engine designs.
The Cummins B-series diesel is perhaps the best-known engine that comes from all those years of experience. That fame is due to the fact that Dodge uses Cummins engines after powering its trucks with Mitsubishi Motors diesel engines. While the straight-six 6BT Cummins 5.9-liter (part of the B-Series agricultural engines) made its debut for use in farm tractors in 1984, it didn’t find its way into Dodge Ram trucks until 1989. The B Series has undergone a number of changes over the years to improve on that original design, eventually bringing us the 6.7 liter Cummins Turbo Diesel that is still available today in heavy-duty Ram pickups. Evolutions include the 1998 5.9L 24-valve ISB and the 6.7L ISBe introduced in 2007.
Reliability of Cummins B-series diesel engines
Owners of the Cummins diesel engines that power the Dodge and Ram pickups are generally considered very reliable. In fact, the 5.9 liter 12-valve Cummins is often considered one of the best truck engines of all time. Bruce Behner, a member of Cummins’ Million Mile Club, purchased his used 12-valve Cummins, which he had already driven 231,000 miles. At the time a video was recorded for the official Cummins YouTube Channel, the truck’s six-digit odometer showed 025,050 miles, having already exceeded the maximum of 999,999.
However, the few problems encountered by the Cummins B-series diesel engines should not go unmentioned. Problems like the great dowel pin and the 53 block are reason enough to be careful if you buy a 5.9 Cummins engine produced from its debut until 2002. The 6.7 Cummins is also not immune to problems, especially from the 2019 model year onwards. These problems mainly involved faulty hydraulic valve lifters that could damage the camshaft. That was also the year Ram began using the infamous Bosch CP4.2 high-pressure fuel pump to feed the 6.7 Cummins.
Fortunately, all the problems – except the 53 block, which will eventually crack – have fairly simple solutions. Some of them, like the high-pressure fuel pump, are already covered for owners who have been recalled.
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