The DaimlerChrysler AG Mannheim plant is celebrating the 500,000th remanufactured engine for commercial vehicles – i.e. trucks, buses and coaches – to leave the assembly line. The landmark unit is an 8-cylinder powerplant from the 500 series.

Mannheim has a long tradition of overhauling and remanufacturing engines, stretching back as far as 1949. Today the plant produces over 5000 of these units per year. An engine overhaul – as an alternative to the classic remanufactured unit – is most suitable for vehicles that have already been in service for much longer than anticipated, since the lower cost is more in line with the vehicle's current market value. However, a certain degree of downtime is involved as the engine has to be dismantled and inspected before undergoing a complete overhaul. Delivery time and costs are discussed with the customer beforehand. In the best-case scenario, an overhauled engine costs 60 percent of the remanufactured unit price. In the worst-case scenario, overhauling a seriously defective engine costs as much as a remanufactured engine, particularly if a lot of parts need replacing. DaimlerChrysler offers a special service for the 6-cylinder Actros engine, the OM 501. Here customers can opt for a 24-hour rapid-response service or, if required, have the engine upgraded from a Euro 2 to the higher Euro 3 emissions rating. Both options carry a surcharge of around 10 percent extra but can quickly pay for themselves as a result of shorter downtime or lower road tax and toll charges.

High mileages

Today's commercial vehicles often clock up high mileages in a relatively short period. It is not uncommon for a high-quality Mercedes-Benz truck, bus or coach to cover a million kilometres or more. Although the vehicle may still be in good condition overall, the heart of the machine can start to display certain weaknesses as time passes.

In this case, the operator can choose between a genuine reconditioned engine and a factory-overhauled engine from Mercedes-Benz. Both alternatives are attractive, cost-efficient solutions, especially if the vehicle has an expensive special body fitted or a high residual value. The Mannheim plant has been dismantling and completely overhauling commercial vehicle engines on a large scale for a number of years. These units are then returned to customers "as new". For their "second lease of life", the engines are supplied with the same warranties as their new counterparts, the only difference being that they are considerably less expensive. Plus they are available within 24 hours when time is really tight. There is also a welcome side-effect in that recycling of the old engines makes a commendable contribution to looking after the environment.

It stands to reason that the best place to overhaul engines is the place where they were built. The know-how is essentially the same, the production technology is similar and the final testing procedures have to be identical if the overhauled units are to be of the same quality. Only a few new procedures are required. Incoming engines have to be fully dismantled, washed and inspected, regardless of how old or defective they are, even if they have suffered fire damage. Parts are sorted based on the "the good into the pot, the bad into the crop" principle. Any remaining scrap is kept so that it can be reused as raw material, whilst usable components are reworked or machined to size. Most of the time, all that really needs to be disposed of are a few seals and oil filters. Then the engine is re-assembled on the assembly line. At the end of the line, the engine receives a fresh coat, making it ready for its new lease of life. Finally the engine is either delivered straight to the customer or sent to the central spare parts store in Germersheim, where it waits to be called up for service.

"Our business is founded on old engines which we take back from our customers using a special "returns" system. If a customer purchases a remanufactured engine through our service organisation, we pay that customer a take-back amount for later returning their old engine, depending on the engine model and condition", says Peter Bohn, head of remanufactured engine and small series production in the Trucks Europe/Latin America business unit of DaimlerChrysler AG in Mannheim. "At the same time, we also buy old engines on the free market."

Remanufactured engine or factory overhaul

If the heart of the machine is starting to show signs of its age, Mercedes-Benz offers a choice of either a remanufactured engine or a factory overhaul. Plus customers can opt for the 24-hour rapid-response service. In the case of remanufactured engines, all defective and worn parts are replaced. Plus all the latest design changes, new features and improvements are incorporated. The remanufactured unit gets a completely new identity, recognisable by its new model plate. Mercedes-Benz provides the same warranty as for new engines. "One-for-one exchange in the workshop" is the more expensive option but ideal when time is tight because the remanufactured engine is simply taken straight "off the shelf". Quality without compromise is also the sensible option if the vehicle still has a long useful life ahead of it or is equipped with a high-value special body.

Same quality standards as for new engine production

Around 200 staff currently work in the engine remanufacturing and overhaul department at the Mannheim plant, dealing with over 2700 engine variants and a total of some 31,000 different parts. When engines are remanufactured, the carefully selected parts have to meet the same quality standards that apply to standard Mercedes-Benz production. All parts subject to wear, such as bearing bushes, valve guides etc. are exchanged. Fast-wearing parts like pistons, cylinder liners, bearings and seals are replaced with genuine new parts during assembly.

The engine parts are remanufactured to a uniform standard, in many cases using the same tools that are employed for initial production, meaning that either remanufactured or new components can be installed. An in-house-developed turbocharger test bench detects even the most minor of quality defects whilst auxiliary units such as injection pumps and starter motors are reengineered by the supplier. Irrespective of actual wear levels, all bearings on a crankshaft are remachined with consistent precision. Following rebalancing, the remanufactured crankshaft is of the same quality as a new part.

Cylinder blocks are machined with a tolerance of a hundredth of a millimetre on the same transfer lines as those used in series production, thus ensuring the same level of quality as that achieved during the production of new parts. Reproducing the original cylinder diameter means that the remanufactured engine has exactly the same displacement as a new unit.

ECU also reprogrammed

Individual programming of the control unit at the end of the remanufacturing process breathes new life into the remanufactured engine. The main difference compared to other overhaulers is that the assembly team in Mannheim has full access to the engine ECU. Independent overhaulers do not usually have this benefit and so are forced to supply the engine without an ECU, meaning that there is no way of telling whether the engine will run without any problems or perform as it is supposed to until it has actually been installed in the vehicle.

A decade of 500 and 900 series engines

The list of engines available in remanufactured format currently includes the 500, 900, 457, 300 and 400 series. Engines in these series can also be overhauled. The V-engines in the heavy-duty 500 series have been tried and tested over a number of years and are one of the main reasons why the Mercedes-Benz Actros enjoys such a first-class reputation and has achieved such success.

These engines are also the flagship powerplants for luxury touring coaches such as the Travego. However, they prove equally adept when used in more rustic applications like combine harvesters.

Atego, Vario, Cito midibus, Citaro urban bus and Unimog vehicles are all powered by 900 series engines, while 457 series engines are used in the Axor and Citaro. Since they were first introduced exactly ten years ago, the 500 and 900 series in particular have set new standards in terms of technology and cost-effectiveness. They are synonymous with low fuel consumption, unbeatably long service intervals and outstanding longevity.

Now discontinued, the old 300 series engines powered the Unimog and the light truck range (LK) that preceded the Atego. Series 400 units were installed in the heavy trucks (SK range) that were the forerunners to the Actros. Again, most of these engines are still remanufactured using the original production facilities. They then go on sale to vintage Unimog enthusiasts, for example.