Engine – Design

Design and Function

Applies to: B5244S4, B5244S5, B5254T3, B5254T7

Engine, general

The entire engine is made of aluminum.

The compact "pent roof" design of the combustion chamber and the V shaped arrangement of the valves optimize injection and evacuation via the intake passage and combustion chamber (cross-flow) and the exhaust passage. The swirl surfaces of the combustion chamber and the centrally positioned spark plug ensures optimal combustion, low sensitivity to knocking and low, stable exhaust emissions.

The pendulum suspension of the engine consists of an engine pad secured to a side member. The cylinder head is "gravity" cast which is a slower process than press casting. This is so that the exhaust and intake ducts and the water and oil mantles are integrated during construction.

Applies from 2006 model year

The engine meets Euro 5 emissions standards.

All bearings are lead free. The screws used are Crome 6+ free.

Cylinder head, camshaft bearing housing

The engine block is divided up into five sections. The cylinder head consists of two sections and the cylinder block of three sections. The seal between the cylinder head and cylinder block is a conventional cylinder head gasket. The seal between the other gasket faces is a liquid gasket.

There is a cover over the sparkplug wells for protection against dirt and water. The two camshafts are carried on six bearing caps each in the two halves of the cylinder head. The upper half is a combined valve and camshaft cover.

It has cast oil ducts on the underneath which ensure good oil supply to the camshafts and the mechanical valve lifters. The lower half contains the maintenance-free mechanical valve lifters, the valve springs and valves.

Cylinder block

The engine block is divided into three sections, the cylinder block, intermediate section and oil pan. The mating flange between the cylinder block and intermediate section is in the center line of the crankshaft.

The cylinder block has five cast iron cylinder sleeves cast into the cylinder block which cannot be replaced. The six main bearing seats have cast iron reinforcements in the intermediate section.

On the top of the intermediate section there are cast oil channels which distribute the oil to the main bearings and on via the crankshaft to the big ends.

The oil pan contributes to the rigid construction and acts as additional reinforcement. There is central smooth-bore oil duct for piston cooling.

Oil pan

The oil pan is made of die cast aluminum with baffles. This is so that the oil does not splash excessively. It is secured in the cylinder block with a liquid LOCTITE gasket, which ensures the seal between the cylinder block and oil pan.

Crankshaft

The crankshaft has six main bearings. The 5th main bearing is a throw-out bearing. At the front end of the crankshaft are two spline joints, the inner of which drives the oil pump. The drive gear for the timing belt and vibration damper is on the outer joint.

A blind spline ensures that the position and control of the drive gear is correct. The connecting rods are forged and the split joint between the connecting rods and the caps gives an exact mounting to the caps.

B5244SX and B5254TX are both equipped with forged crankshafts which give maximum strength and contribute to a low noise level.

Piston

The piston has a homogenous aluminum alloy with graphite coating on the sides. This coating gives reduced friction and noise. The piston rings are of different materials depending on where they are located on the piston. The upper compression ring is a nitrated steel ring. The lower compression ring is manufactured from cast iron and the oil scraper ring is a three piece design, all made of nitrated steel (does not apply to B5xx4Sx). For B5244S7 engines the oil scraper ring is two piece instead of three piece. It is more wear resistant than the three piece ring. The ring height is 2.5 mm compared to 2.0 mm for the three piece ring.

The piston pin is hardened steel and is held together using steel snap rings. The piston is oval and conical and flat at the top. By reducing the area from the upper piston ring to the top of the piston, the release of hydro-carbons from the engine to the three-way catalytic converter (TWC) is reduced.

The pistons are oil cooled so that they can have a lower compression height. Oil is led through a valve in a longitudinal channel in the lower section of the cylinder block on the exhaust side. There is a nozzle screwed to the channel at each cylinder. This leads the oil towards the underside of the piston.

Camshafts, Valve system

The camshafts are cast iron. The cam lobes which press against the valve lifters are hardened to tolerate the contact pressure. The valve lifters are steel and mechanical, not hydraulic.

There is a certain amount of valve clearance between the valve lifters and cam lobes. The valve clearance is adapted to compensate for differences in length between the valve and cylinder head due to expansion when warming up. Mechanical valve lifters ensure more precise valve timing, reduced friction, more stable combustion and reduced mass.

The material in the lifters is case-hardened steel. The surfaces between the camshaft and valve are slightly convex to guarantee centered contact.

Camshaft transmission

The timing belt which drives both the camshafts and the coolant pump is a conventional single tooth belt. The camshaft's pulley wheels are secured by three screws in each camshaft. The holes for the screws are oval to allow the correct setting of the camshaft positions.

The timing belt tension is retained by a mechanical belt tensioner. The belt tensioner presses the belt via a tensioner roll installed on a lever. The idler wheel on the other side of the belt prevents the belt from swinging.

Auxiliaries belt

The auxiliary equipment consists of two belts and two auxiliary units. The auxiliary units (generator (GEN), Air conditioning (A/C) compressor) are driven by two Poly-V drive belts tensioned by a mechanical tensioner. The belt tensioners are all located on a bracket that connects the auxiliary units (generator (GEN), Air conditioning (A/C) compressor).

The generator (GEN) receives its power via the air conditioning (A/C) compressor and the air conditioning (A/C) compressor receives its power through the vibration damper which is located on the crankshaft. The power steering pump is driven by an electrical hydraulic pump.

Mechanical timing belt tensioner

The tensioner consists or a spring and a friction element. The friction element provides the required damping to absorb small oscillations and speed variations. The spring ensures correct belt tension, irrespective of wear and temperature. The belts are made of cord reinforced rubber.

Lubrication system

The oil is led from the oil pan via a suction piece to the oil pump. The oil pump is located on the cylinder block. The oil is then pumped onwards to the oil cooling system and then to the oil filter. The oil flows from the filter through a cast oil duct in the intermediate section to the main bearings. The oil then flows through drilled channels in the crankshaft to the connecting rod bearings.

The camshafts are supplied with oil by a bored channel in the cylinder block. The channel runs through the cylinder head, where it flows out at the bottom of the upper half of the cylinder head. There is a cross duct in the channel to the cylinder head which carries oil to the pistons via a piston cooling valve.

The oil flows on via an oil duct to the bearing for the left-hand camshaft and the valve lifters (intake side). The bearings for the right-hand side camshaft (exhaust side) are supplied by a cast cross duct at the front edge of the upper half. This cast cross duct also supplies pressurized oil to the solenoids for the VVT unit. Drain holes in the cylinder block release the oil from the cylinder head and crankshaft bearing back to the oil pan.

Oil filter

The oil filter holder is made of die cast aluminum. It is on the cold side of the engine. The oil filter cover is plastic. There is a by-pass valve in the cover. A O-ring in the cover ensures that it is sealed.

Piston cooling valve

The piston cooling valve is manufactured in steel with a hardened piston, a spring and a spring stop. A copper washer ensures that oil does not leak onto the cylinder block.

Injector

The valve is enclosed in a plastic casing with O-rings on each end which act as seals. There is a coil in the valve which creates a magnetic field. This overpowers the force of the spring which holds the fuel needle in place. The fuel is let through and mixes with the intake air.

Evaporative emission (EVAP) system

The housing for the evaporative emission system (EVAP) valve is plastic and contains a solenoid valve. The evaporative emission system (EVAP) canister consists of a plastic holder with active carbon and a filter. Internally, the plastic holder is divided up into chambers depending on the market and the prevailing emissions requirements.

All the active carbon in the canisters is held by springs and pressure plates so that no air columns are created by vibration for example. This could lead to hydrocarbon leakage at the carbon beds. The connector pipe has a filter so that carbon dust cannot leak out and damage the leak diagnostic pump and the EVAP valve.

The leak diagnostic pump consists of a plastic housing with an electric motor, pump, valves, leak calibration and a PTC heater element.

Intake system

The intake system is divided into two sections, the upper and lower intake manifolds. The upper intake manifold is made of plastic for naturally aspirated and turbocharged engines. The lower intake manifold is aluminum for both types of engine to protect the fuel injection nozzles in the event of a collision.

The intake system for naturally aspirated engines has a total volume of 5.3 liters with fixed barrel lengths. On turbocharged engines the total volume is 3.0 liters with short barrels.

The gasket between the lower intake manifold and cylinder head on naturally aspirated engines is a calibrated single gasket. On turbocharged engines there is a double gasket with a built in non-return valve.

Throttle body (TB)

The throttle body (TB) is die cast aluminum. The throttle disc is brass on naturally aspirated engines and aluminum on turbocharged engines. The position sensors are under the plastic cover. These read the position of the throttle disc. There are also two connections to the engine in the cover. These turn the throttle disc to the angle requested by the driver.

The throttle body (TB) does not need to be cooled, but may need to be heated. An O-ring in the intake manifold ensures the seal between the intake manifold and throttle body (TB).

Turbocharger (TC)

The integrated manifold and turbine housing are made of austenite forged steel to tolerate exhaust temperatures up to 1050 °C.

The bearing housing and turbine housing are held together by a V-shaped clamp. The compressor housing is made of die cast aluminum. The bearing housing is cooled by the oil and coolant system to prevent coking in the bearing for the turbine shaft which spins at up to 170,000 rpm.

Exhaust system

The exhaust system primarily consists of four sections. Manifold (and turbocharger (TC) if the engine is turbocharged), three-way catalytic converter (TWC), heated oxygen sensors (HO2S) and muffler. The exhaust system is manufactured from chromium steel sections welded together.

The pipes are specific lengths so that the gases flowing from the cylinders do not interfere with each other and so that there is good flow distribution in the three way catalytic converter (TWC). There is a boot on the three way catalytic converter (TWC) to absorb engine movements and any manufacturing and installation tolerances.

Heated oxygen sensors (HO2S) are used to control the engine and monitor the three way catalytic converter (TWC). One heated oxygen sensor (HO2S) before and one heated oxygen sensor (HO2S) between the stones. In the B5244S7 an additional heated oxygen sensor (HO2S) is located in the manifold.

The entire exhaust system is manufactured in chromium steel. A three-way catalytic converter (TWC) consists of perforated ceramic beads or metal substrates. These are coated with a washcoat. The washcoat contains precious metals among other things.

Flame trap

The flame trap is made of die cast aluminum and integrated with the oil filter. The cyclone separators are plastic and cannot be replaced.

Cooling system

The coolant pump pumps coolant through the cylinder block, and also cools the cylinder head, cylinder sleeves, spark plug wells, intake ducts and fuel injection nozzles.

The coolant flows in at the pump and passes through a number of channels before it collects and then flows out to the thermostat housing. If the thermostat housing is closed, the coolant passes via the by-pass channel directly to the coolant pump to then circulate through the cylinder block again.

In principle, its appearance is the same as the oil cooler for the transmission. Both have an inlet and outlet. The oil cooler is constructed in layers where water and oil flow around each other. Having flowed through the restrictions in the oil ways, the pressure in the system falls.

When the fuel combusts in the engine, the result is both mechanical work and excess energy. The excess heat is taken away from the engine via the exhaust gases by convection to the air in the engine compartment and also by transfer to the coolant and engine oil. The cooling system is a closed system.

B5244S6

Engine B5244S6 has a Premair sensor on the cooling system. This sensor is described in design and function, engine control module (ECM).

Radiator

The radiator is made of aluminum to tolerate the thermal variances when the radiator is being both cooled by cool air and heated by hot coolant.

Thermostat

The thermostat is in the thermostat housing which is in the connection to the coolant outlet from the cylinder head. At the heart of the thermostat is a wax body which expands with energy in the form of heat. In modern cooling systems, the thermostat begins to expand when the surrounding coolant temperature is 90 °C.

Applies to: 2008–2010; D4204T

Engine, general

See: Engine, general

Lubrication system

Oil pump

1. Oil pump chain wheel
2. Oil pump housing
3. Oil screen
4. Pressure reduction valve
5. Mounting screws
6. Blind cover plug.

The oil pump is located on the transmission side of the engine, in the oil trough.

An oil pressure control valve is built into the oil pump housing. This valve opens at an oil pressure of approximately 800 kPa.

The oil pump is a rotor pump. It is powered by the camshaft via a short chain.

Oil filter

1. Oil filter housing
2. Oil cooler

The oil filter is a filter insert. There is a duct in the oil filter housing that is exposed when the oil filter is disassembled. Any remaining oil runs down into the oil pan and further spillage is eliminated.

The oil cooler is a plate oil cooler. The unit is connected to the coolant system. The coolant is routed through the oil cooler and on to the thermostat housing.

The oil cooler is also a coolant heat exchanger. The unit is located on the side of the cylinder block, level with cylinder 2.

There is a blind cover plug on the oil filter insert for sealing the drain hole for the oil filter housing.

When replacing the oil filter cartridge, the plug is pulled out together with the oil filter cartridge. The oil can run back to the oil trough via the housing, which mean that contaminants through leaking oil are prevented.

The unit is connected directly to the engine cooling system via a connection and a hose.

Oil pressure switch

1. Oil pressure switch

The oil pressure switch is located to the right by the oil cooler.

The minimum oil pressure of 50 kPa is monitored via the oil pressure switch. If this pressure is not achieved, the oil filter remains closed for safety reasons. The switch is connected via a conventional cable to the engine control module (ECM).

Oil injection pipes

1. Banjo screws
2. Oil injection pipes

The piston heads are cooled from beneath with oil from the oil injection pipes. The oil injection pipes are secured with banjo screws in the cylinder block.

The banjo screws are connected to the engine lubrication circuit.

The banjo screws contain valves that open the supply to the oil injection pipes when the oil pressure is approximately 50 kPa.

Fuel system

1. Fuel volume control valve

2. High pressure pump

3. Fuel pressure control valve

4. Drive shaft with eccentric

5. Internal feed pump

A. Fuel return

B. Connection for fuel rail

C. Inlet from the tank

The pump consists of the following main components:

• Internal feed pump that draws fuel from the tank via the fuel filter to the high-pressure pump. The feed pump also supplies the high-pressure pump with fuel for lubrication. The pump is a vane-type pump
• The fuel volume control valve, which regulates the fuel flow to the high-pressure pump according to the current need
• The high-pressure pump, which supplies the fuel rail and the injectors with fuel at high pressure
• The fuel pressure control valve, which regulates the fuel pressure from the high-pressure pump before the fuel reaches the fuel rail and the injectors.

1. Injector
2. Fuel dosing valve
3. High-pressure control valve
4. Diesel pump
5. Fuel rail
6. Fuel pressure sensor.

The engine has a common rail injection system from Siemens.

The diesel pump contains an integral feed pump, which feeds the fuel from the tank to the diesel pump.

Diesel pump

1. High-pressure outlet for fuel rail
2. Inlet from fuel filter
3. Fuel volume control valve
4. Return to fuel tank
5. High-pressure control valve

The diesel pump is located on the transmission side of the cylinder head and is powered directly by the exhaust camshaft via a flange.

The diesel pump has three high-pressure pump elements that are located with a 120° separation.

The feed pump is integrated in the diesel pump and is located on the flange. The feed pump is a vane-type pump.

The fuel dosing valve is located in the inlet channel between the high-pressure pump elements and the feed pump. It is controlled via pulse width modulation by the engine control module (ECM).

The three high-pressure outlets for the high-pressure pump elements have been brought together into a single high-pressure connection.

The high-pressure control valve is located by the high-pressure bore for the fuel rail. The fuel pressure regulator is activated by the engine control module (ECM).

Fuel rail

1. Fuel pressure sensor.

The fuel rail is made from forged steel and is mounted directly in the cylinder block.

The fuel is supplied from the diesel pump to the fuel rail via a single delivery line.

From the fuel rail, the fuel is led to the injectors via four more delivery lines.

Fuel filter

1. Inlet from fuel tank
2. Connection to diesel pump
3. Electrical fuel preheating
4. Drain screw.

The fuel filter is located above the fuel rail and is mounted in a holder on the cylinder head.

The fuel filter has electrical fuel preheating, which is located in the middle of the filter, between the inlet and the outlet connections.

The fuel filter and the housing constitute a single unit that can only be replaced as a complete unit.

The fuel filter has collision protection.

Injectors

1. Delivery line connection
2. Connector
3. Retainer
4. Copper seal
5. Plastic socket
6. Return line connection.

The injectors are located in the center of the top of the cylinder head, and are secured in holders.

The guide sleeves in the lower section of the cylinder head and the plastic sleeves for the injectors provide correct centering.

The seal with the combustion chamber is provided with a copper washer between the injector and the cylinder head. This must always be replaced when installing.

The return lines are secured on the top of the injectors and connected in series to each other.

The use of piezoelectrical material for controlling the injection sequences provides a number of benefits compared to injectors that work with electromagnetism:

• up to four times faster
• only one impulse is required to start injection and one impulse to terminate injection
• low power consumption
• the combination of low current and impulse control means that less energy is required for each injection sequence
• the speed means that the injection times can be controlled extremely precisely, which ensure great accuracy as regards the amount of injected fuel
• the system is not sensitive to electromagnetic effects.

Additive tank, applies to S40 (04-), V50, C30 and C70 (06-)

1. Additive Dosing Module (ADM)
2. Additive tank with integrated pump and level sensor
3. Ventilation valve for tank
4. Feeder hose and injector
5. Main fuel tank (diesel)
6. Overflow valve (when filling)
7. Refilling connection for additive

The additive system consists of the additive dosing module (ADM), additive tank, a mechanical injector on the main fuel tank and the feeder hose for additive.

The additive tank is made of polyethylene plastic.

The additive tank has a refilling connection for additive and a ventilation valve. The tank has an overflow valve. This valve releases any excess additive during refilling when the tank is full. There is a pump and level sensor inside the additive tank.

The pump is integrated in the additive tank. It is positioned on the side of the tank housing. The pump cannot be replaced as a separate component. The entire additive tank must be replaced as a single unit.

The level sensor provides the additive dosing module (ADM) with information about the prevailing additive level in the separate tank. The level sensor is integrated in the additive tank. It is positioned on the bottom of the tank housing. The level sensor cannot be replaced as a separate component. The entire additive tank must be replaced as a single unit.

For more information, see Design and Function, Additive Dosing Module (ADM).

Vacuum system

Overview

Hose 1

Hose 2

Hose 3

Hose 4

EGR system

1. Exhaust gas recirculation (EGR) cooler
2. Connector pipe to intake manifold
3. Connector pipe to valve cover / air cleaner (ACL)
4. EGR stepper motor
5. Connection to the cylinder head.

The EGR system consists of an EGR stepper motor, and EGR cooler and a connector pipe to the intake manifold.

Catalytic converter

The catalytic converter is an oxidation catalytic converter which reduces CO and HC emissions.

Its location, immediately after the turbocharger (TC), known as a CCC (Closed Coupled Catalyst), means that the catalytic converter rapidly reaches the correct operating temperature.

Turbocharger (TC)

1. Turbocharger (TC) position sensor
2. Turbocharger (TC) housing
3. Gasket
4. Adapter
5. Oil return hose
6. Retainer
7. Banjo screw
8. Oil line
9. Banjo screw

The turbocharger (TC) control valve steplessly regulates the vacuum in the pressure regulator which control the turbine position, (Variable Nozzle Turbine, VNT).

In principle the valve can vary the pressure from absolute vacuum to atmospheric pressure. This allows the guide rails for the turbocharger (TC) to be regulated steplessly, which means that the desired boost pressure can be achieved.

The engine control module (ECM) controls the position of the control valve and hence also the position of the valve.

Cooling system

Coolant circuit

1. Heat exchanger
2. Thermostat housing
3. Bypass valve (S40 (04-), V50 -2005)
4. Thermostat
5. Shut-off valve
6. Oil cooler
7. Coolant heat exchanger
8. Cooling system expansion tank
9. Cylinder block
10. Coolant Pump
11. Exhaust gas recirculation (EGR) cooler

The coolant flow is dependent on the following components:

• bypass valve (3)
• thermostat (4)
• shut-off valve (5)
• engine coolant temperature (ECT) sensor
• engine control module (ECM).

Due to the high efficiency of the diesel engine and consequently the relatively small heat losses, it can be difficult to maintain a comfortable temperature in the passenger compartment at low outside temperatures. The purpose of the various components is, on the basis of the coolant temperature, to regulate the coolant flow to the heater element in the passenger compartment so that coolant heating takes place as quickly as possible.

Thermostat housing

1. Bypass valve
2. Connection to the cooling system expansion tank
3. Connection to cooler inlet
4. Connection to coolant heat exchanger
5. Connection to cooler outlet
6. Connection to coolant pump
7. Connection to heat exchanger
8. Engine coolant temperature (ECT) sensor.

In order to achieve rapid heating of the coolant, and therefore a comfortable temperature in the passenger compartment, the engine cooling system has:

• a thermostat housing
• an electrically controlled bypass valve
• an electrically controlled shut-off valve.

The thermostat housing is located on the cylinder head on the transmission side of the engine.

The engine temperature sensor is located in the thermostat housing and is secured with a clip. The thermostat housing also houses the thermostat and the bypass valve. The thermostat is a conventional type.

The thermostat housing is made of plastic and cannot be dismantled during service work. The engine coolant temperature (ECT) sensor can be replaced separately.

For further information about the components, see Design and Function, engine control module (ECM).

Coolant Pump

1. Gasket
2. Coolant Pump

The coolant pump is located on the transmission side of the engine and is powered via a toothed belt.

The coolant pump housing consists of an aluminum alloy and is secured using 5 screws.

The pump housing is made of an aluminum alloy. The gear wheel is made of plastic. The gasket between the pump and the cylinder block comprises a metal frame that is coated with rubber.

A rubber-coated metal gasket is used for the coolant pump seal with the cylinder block.