Scania DSC9 DSC 9 Engine Workshop Manual

DSC 9 Engine Workshop SCANIA Manual This manual covers the following engines up to 1996 3 Series Trucks DSC 9 10 (220Hp) DSC 9 07 (250Hp) DSC 9 09 (250Hp) DSC 9 08 (280Hp) 4 Series Trucks DSC 9 11 (220Hp) DSC 9 12 (260Hp) DSC 9 13 (310Hp) Manual Contents: Description of Operation ..... Engine Overhaul Description C M0 from the library of Barrington Diesel Club 2 18

SCANIA service Contents 9 ENGINE Function description Contents Cylinder block ...................................... 2 Pistons 3 Connecting rods ................................. 5 Crankshaft 6 Valve rocker mechanism ..................... 8 Timing gears ...................................... 9 Lubrication system ................................. 10 Turbocharger ...................................... 14 2-2 from the library of Barrington Diesel Club

Cylinder block SCANIA service Cylinder block The cylinder liners are exchangeable. A steel gasket for each cylinder acts as a seal between cylinder liner and cylinder head. The cylinder liners protrude somewhat above the plane of the cylinder block, thereby pressing the gasket hard against the cylinder head for proper seal. The seals for the coolant and oil passages consist of rubber rings. '' •// H y /./, The lower part of the cylinder liners is able to move to a certain extent to allow for heat expansion. The seal consists of three rubber rings atdifferent heights on the lower part of the liner. Between the two lowermost rings there is an tell-tale hole that continues to the outside of the cylinder block. If coolant appears in any of these holes it is a sign that the seals are leaking. This is a warning to change the seals. 2-3 from the library of Barrington Diesel Club

SCANIA service Pistons Pistons The pistonsare made of aluminium alloy. This provides for a piston of high strength, low weight, limited heat expansion and good heat dissipation. To enable the piston to withstand the high pressure and temperature in the combustion chamber the piston crown and ring section is thicker than the rest of the piston. The tapered shape of the connecting rod little end makes the piston more rigid. As the temperature is higher in the piston crown the piston diameter is somewhat smaller there to allow for the larger heat expansion. 2-4 from the library of Barrington Diesel Club

Pistons SCANIA service An indentation inthe piston crown forms the combustion chamber. It is shaped like a bowl with a raised centre. The shape of the combustion chamber makes the intake air sw irl. This contributes to optimum fuel/air mixture when the fuel is injected and effective combustion. To make the piston slide easily, clearance is needed between the piston and cylinder wall. The function of the piston rings is to seal the gap made by this clearance and to dissipate heat from the piston. The piston has two compression rings. The uppermost compression ring is exposed to higher temperature and pressure than the other rings. Therefore, the load on the upper compression ring groove is higher. To alleviate wear a ring of cast-iron is cast into the piston. The piston has an oil scraper ring. This ring prevents oil from penetrating to the combustion chamber where it would be consumed. On the inside of the oil scraper ring there is an expanderthat assists in pressing the ring against the cylinder wall. The expander is of the helical spring type. The piston and the shape of the piston rings are very important to the operational reliability of the engine, to the lubrication oil consumption and the fuel consumption. ^ -5 1:792 from the library of Barrington Diesel Club

SCANIA service Connecting rods Connecting rods The little end of the connecting rod is tapered. This provides for a wider bearing area in both piston and connecting rod. 0) The big end is split at an angle whereby piston and connecting rod can be pulled up through the cylinder. To prevent the connecting rod cap from being displaced in relation to the connecting rod the contact surfaces have flutes. For proper location in the other direction when fitting the cap there are grooves with locking pins. 2-6 1:797 from the library of Barrington Diesel Club

Crankshaft SCANIA service Crankshaft Each compressions stroke acts as a brake on the crankshaft and each combustion stroke strives to increase the crankshaft rotation speed. Twice in each revolution the pistons and connecting rods change direction of movement. Thereby the crankshaft is subjected to frequent force impulses in each revolution. The quality of the metal is important to the service life of the crankshaft. Very high demands are also made on shape and surface treatment. The hardening of the crankshaft journals is sufficiently deep to enable regrinding several times. As axial bearing for the crankshaft there are thrust washers by the rearmost main bearing. Different thicknesses of thrust washers enable adjustment of crankshaft end float. Main bearing and big end bearing shells consist of three layers. The outer layer, the backing, is of steel, the middle layer is of lead bronze and the layer in contact with the crankshaft journal is of lead and indium, or lead, tin and copper. It isthe latter layer that is normally subject to wear. CjjLpf&i-' 2-7 from the library of Barrington Diesel Club

SCANIA service Crankshaft The shocks from the connecting rods generate torsional oscillation in the crankshaft. The amplitude of such oscillation is at its highest at a certain engine speed. Torsional oscillation is generated as follows: Imagine that the rear end of the crankshaft and flywheel rotate at an even speed through the whole turn. In relation to the flywheel the front end of the crankshaft will rotated at a higher and lower rate several times during the turn. - The oscillation would cause noise to be issued from the timing gears and in extreme cases crankshaft breakage. To prevent this there is an oscillation damper on the front end of the crankshaft. In the circular, fully encapsulated housing of the oscillation damper there is a steel ring. The housing is attached to the crankshaft. Between the housing and ring there is adhesive oil that retards the relative movement between ring and housing. As the ring strives to turn at an even speed the oscillation in the front end of the crankshaft will be suppressed. 2-8 t.«ol from the library of Barrington Diesel Club

Valve rocker mechanism SCANIA service Valve rocker mechanism The valve rocker mechanism opens and closes the valves with correct timing in relation to the piston movements. The camshaft is driven by the timing gears to make it turn at half the speed of the crankshaft. The lobes on the camshaft, two for each cylinder, actuate the valve tappets. Each push rod has one end in a valve tappet and the other end under a rocker arm. In the rocker arm there is an adjusting screw which has a ball shaped lower end that rests in the push rod. The adjusting screw is used for setting the valve clearance. Each valve has two compression springs. The function of the springs is to close the valve and return the rocker arm and push rod to make the valve tappet follow the camshaft at all times. 00 O CT> The valve tappets are housed in the side covers of the cylinder block and follow the side covers when removed. The valve seat rings are pressed into the cylinder head. They are made of a special resistant metal to provide for long service life. If necessary, however the valve seat rings are exchangeable. 2-9 from the library of Barrington Diesel Club

SCANIA service Timing gears Timing gears The crankshaft drives the camshaft and injection pump via an intermediate gear. The camshaft and injection pump turn at half the speed of the crankshaft. The oil pump is driven via another intermediate gear by the crankshaft gear. In addition to above gears there is a gear for: - Air compressor for brake system. Hydraulic pump for servo steering. To facilitate assembly the gears are marked There is one engine execution for power take-off. The power take-off is driven via an intermediate gear. 2-10 from the library of Barrington Diesel Club

Scania DSC9 DSC 9 Engine Workshop Manual

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