Connecting pistons to connecting rods and installing them in the cylinder block (Mercedes-Benz Vito W639)

The connection of the pistons to the connecting rods is made using piston pins.

The piston pins (6), installed in place, are secured with spring retaining rings measuring 30x2 mm. In this case, the connector of the retaining ring must be directed upwards.

When assembling, the arrow marked on the piston (4) at the top must point towards the timing belt.

You should also pay attention to the relative orientation of the piston and connecting rod (for this purpose, marks must be applied during disassembly).

Installing connecting rod bearing shells

Before installing the liners, clean the seating areas and blow out the lubrication channels with compressed air.

When installing, pay attention to the alignment of the lubrication holes of the liners and the holes of the oil channels (shown in the figure VN arrows).

Crankshaft connecting rod bearing shells. Comparison with the dimensions of the crankshaft connecting rod bearing journals

Note: The number 611 in the part number means that the engine uses a part designed for the QM611 engine.

Checking the connecting rod bearing cap fastening screws

Before installation, screws securing the connecting rod bearing caps (thread M8 x 1) should be checked for excessive elongation. Screws that are longer than the maximum permissible length must be replaced with new ones.

Length of new screw: 47±0.3 mm.

Maximum length allowed: 48 mm.

Tightening the connecting rod bearing cap screws

Article was borrowed from the website Mercedesman.ru

Before installation, apply a thin layer of motor oil to the threads and contact surfaces of the screw heads.

Initial tightening after breaking off (in the original; At initial tightening torque after cracking): 5 Nm + 25 Nm + 180°.

Subsequent cases of tightening (in the original: For subsequent tightening): 5 Nm + 25 Nm + 90°.

Note: Initial tightening torque information is provided in the manufacturer's materials, which may mean that connecting rods manufactured using the technology described below can be used.

The initial tightening of the screws after breaking off the cover from the connecting rod blank is carried out with an increased tightening torque. Most likely, we are talking about a modern method of manufacturing connecting rods, in which the connecting rod and cover are made and processed as one piece. Then, using a special technology, the cover is broken off from the connecting rod. This creates a unique fracture surface that is specific to only this pair of parts (note, ed.).