How to use this chapter
This part of Chapter 2 describes repair work that can be carried out without removing the engine from the vehicle. If the engine is removed from the vehicle and will be disassembled as described in Part D, all preliminary steps for disassembling the engine can be skipped. Note that although it is physically possible to overhaul such components as the connecting rod and piston group without removing the engine from the vehicle, these operations are not carried out separately. Usually, some additional operations must be carried out (not counting cleaning of parts and oil channels). For this reason, such operations are classified as basic actions and are described in Part D of this chapter.
Part G describes the removal of the power unit from the vehicle and the repair operations that can then be performed.
Engine Description
The engine is a four-cylinder, in-line, single overhead camshaft mounted in-line ("north-south") with the transmission located at the rear of the car.
The crankshaft is mounted in a cast iron cylinder block on five main bearings. Axial movement is controlled by thrust half rings installed on each side of the middle main bearing.
The connecting rods are attached to the crankshaft using horizontally cut connecting rod bearings, and to the pistons using pressed piston pins. Three piston rings are installed on the pistons: two compression rings and one oil scraper ring.
The camshaft is driven by a camshaft sprocket from a single-row or double-row chain (depending on the engine type). The chain also drives an additional shaft, which is used to drive the distributor, as well as the fuel pump, on carburetor models.
The camshaft is supported in five bearings on the aluminum alloy cylinder head and operates the valves via levers called cams. On early models, the valve clearances are manually adjusted. On later models, the valves are operated by hydraulic tappets mounted on the cams, and regular manual adjustment is not required.
The gear oil pump is driven directly by the crankshaft and is located on the camshaft drive chain housing.
Repair operations available without removing the engine from the vehicle
Without removing the engine from the vehicle, it is possible to perform the following work:
- a) Cylinder head - removal and installation.
- b) Camshaft drive chain covers and sprockets - removal and installation.
- c) Camshaft - removal and installation.
- d) Pallet - removal and installation.
- d) Camshaft drive belt - removal and installation.
- e) Removal and installation of connecting rod bearings, connecting rods and pistons*.
- g) Oil pump - removal and installation.
- c) Powertrain mounts - replacement.
- i) Flywheel/drive faceplate - removal and installation.
(Full article available on the resource: MercedesMAN)
* To successfully complete this operation, it is recommended to remove the engine.