Note: This chapter describes the most important engine maintenance and repair procedures, excluding procedures that require special skills and tools (for example, a major engine overhaul), - these works should be entrusted to auto service specialists.
The engine code consists of three (1st letter - "B") or four (1st letter - "C") letters; the first three of them represent the mechanical design and engine displacement, and the fourth (if available) means the engine characteristics depending on its control unit. The engine serial number consists of six characters. If more than 999,999 engines are produced, the first digit in the number is replaced by a letter. The engine code is indicated on the vehicle data sticker and on the manufacturer's plate (see Introduction). The first three characters of the engine code and its serial number are stamped on the cylinder block (see illustrations 1.1a-b).
1.1a. Code and number of 3.0 TDI engines (on the front side, covered by the intermediate roller of the drive belt).
1.1b. Code and number of 4.2 TDI engines (on the inside of the cylinder block, under the left intake manifold).
The 3.0 TDI engine code and its serial number are additionally indicated on a sticker located on the intake manifold.
The engine is mounted longitudinally in the engine compartment located at the front of the vehicle.
Preparatory operations
Before performing any engine maintenance procedures, clean the engine compartment and external surfaces of the power unit using a special solvent. This treatment will prevent dirt from getting inside the engine.
If necessary, depending on the nature of the work to be done, the hood can be removed to provide free access to the components to be serviced (see Chapter 11). To avoid accidental damage to the paintwork, cover the car's fenders with special covers or old blankets.
Excessive engine oil consumption can be considered a signal that it is necessary to check the condition of the piston rings, valve stem seals and/or valve guides. Naturally, first of all, you should make sure that oil losses are not associated with the development of external leaks. Check the compression in the cylinders (see Section 2) to determine the general condition of the engine.
Loss of power, instability of speed, excessive valve noise and increased fuel consumption are usually quite characteristic signs that an engine overhaul is needed, especially when all of these factors occur simultaneously. If performing a full range of adjustments does not help to eliminate the problems, the only solution will be to carry out general mechanical work to restore the engine.
A major overhaul of a power unit involves restoring all its operating parameters to the level typical of a new engine. During a major overhaul, piston rings must be replaced and cylinder mirrors must be restored (turning and/or honing). Typically, the crankshaft main and connecting rod bearings are replaced; if necessary, the journals can be turned and restored. Maintenance of valves is mandatory; their condition at the time the need for a major engine overhaul almost certainly leaves much to be desired. In parallel with the general repair of the power unit, a restorative repair of the starter and generator is usually also carried out.
Note: Critical cooling system components such as hoses, drive belt and thermostat must be replaced with new components during an engine overhaul. In addition, the condition of the radiator should be carefully checked (see Chapters 1 and 3). If signs of developing leaks or obstruction are detected, the radiator should be replaced. Don't forget to check the condition of the oil pump as well.
A major engine overhaul does not require a high level of professional training from the operator, but it does take a fair amount of time. You should plan to stop using the car for at least two weeks, especially if you need to seek help from a machine shop for the purpose of performing individual restoration work.
Most of the work can be done using a standard set of metalworking tools, but some of the tests to determine the suitability of individual components for further use require the use of precision measuring equipment. In doubtful situations, seek help from service station specialists.
Note: Do not forget that the decisive factor in the question of the advisability of performing a major overhaul of the engine is the condition of its cylinder block. It is often cheaper and more reliable to replace a worn-out engine with a refurbished one.
All removed electrical wiring ties and clamps must be installed in their original locations during installation. Electrical wiring and hoses should be laid in the same way. how they were located before removal. Therefore, you should remember or draw/photograph the location of clamps, electrical wiring and hoses.
In conclusion, it can be noted that all efforts to carry out restoration work on worn components will be wasted if the requirement of maintaining cleanliness during engine assembly is neglected.