Engine Mercedes OM602

A series of diesel engines Mercedes OM 602 of 2.5 and 2.9 liters was assembled from 1985 to 2001 and installed on many popular models of the concern, such as W124, W201, W210 or W463. In addition to the pre-chamber versions of the engine, a modification with direct fuel injection was offered.

Since 1987, G-class cars have been equipped with the next generation diesel engines, which by 1989 have completely replaced the previous series. These are pre-chamber 5-cylinder atmospheric diesel engines OM602.931 (2.5l, 90hp), OM602.942 (2.9l, 100hp), b-cylinder diesel OM603.931 (3.0l, 113 HP) and 6-cylinder turbodiesel OM603.972 (3.5L, 150 HP). Their main features are: hydraulic tappets in the valve drive, aluminum cylinder head, high-pressure pump with automatic bleeding to remove air.

Specifications

Motors of this series are more high-speed, are less noisy, more power per liter and more efficient. On them, there are frequent failures of hydraulic pushers due to deterioration of lubrication conditions, accompanied by a characteristic knock of valves. The OM602.942 engine was installed on the Mercedes G290 and Ssang Yong Musso.

Untimely replacement of the chain and dampers, as well as a defect in the hydraulic tensioner can lead to its breakage, which very often completely destroys the block head (on engines of the previous series, the camshaft usually broke, but the head remained intact). Therefore, the gas distribution mechanism must be periodically checked and after a run of 200 thousand km, it is imperative to change the chain, dampers and tensioner.

In 3.5 liter engines, there are frequent cases of burnout of the head gasket between the cylinders, and sometimes even in the absence of any significant violation of the temperature regime. Apparently, this is due to the smaller distance between the cylinders, because the 3.5-liter engine is made on the basis of the 3-liter OM603.962 turbodiesel and the increase in the working volume is achieved by increasing the cylinder diameter from 87 to 89 mm and the piston stroke from 84 to 92.4 mm.

It is interesting to note that the 5-cylinder 2.9-liter OM602.942 engine, which has the same bore and stroke, is completely uncharacteristic of this defect, apparently due to the lower power and lack of turbocharging. A common defect is the appearance of an oil leak from under the cover of the brake booster vacuum pump (this malfunction was less common on older type motors).

Modifications OM602

The most famous modifications:

• 912 is a power unit with a working volume of 2497 cubic meters. see It develops a power of 94 hp. There are 2 valves per cylinder.
• 911 – same displacement, but higher power – 90 hp There are 4 valves per cylinder.
• 962 – a version of the engine with a turbine, with the same displacement, but already developing 126 hp. Valves per cylinder 2.

Characteristics of other modifications:

Frequent problems

• strong vibrations of this diesel engine negatively affect the life of its bearings;
• the timing chain serves about 200-250 thousand km, and if it breaks, the block head cracks;
• when using cheap or old antifreeze, it often pierces the cylinder head gasket;
• from low-quality oil, hydraulic lifters can knock on a run of 90,000 km;
• the owners are also faced with a lot of problems with the injection pump’s vacuum control system.