Discovery 2. Manual — part 406

ENGINE - TD5

DESCRIPTION AND OPERATION 12-1-21

Crankshaft

1 Front end to crankshaft sprocket
2 Oil supply cross-drillings
3 Main journals
4 Big-end journals
5 Rear end to flywheel

The crankshaft is constructed from cast iron and is surface-hardened. The areas between the crankshaft journals and
the adjoining webs and balance weights are compressed using the cold roll process to form journal fillets.

Cross-drillings in the crankshaft between adjoining main and big-end bearings are used to divert lubrication oil to the
big-end bearings.

A torsional vibration damper is attached to the crankshaft pulley by three bolts.

The crankshaft is carried in six main bearings, with end-float being controlled by thrust washers positioned on both
sides of No. 3 main bearing.

Main bearings
There are six main bearings used to carry the crankshaft. Each of the bearing caps are of cast iron construction and
are attached to the cylinder block by two bolts.

The bearing shells are of the split cylindrical type. The upper half bearing shells are grooved to facilitate the supply of
lubrication oil to the bearings and fit into a recess in the underside of the cylinder block. The lower half bearing shells
are smooth and fit into the bearing caps.

Steel-backed thrust washers are included at each side of No. 3 main bearing to control crankshaft end-float. One side
of each of the thrust washers is grooved, the grooved side of each of the thrust washers is fitted facing outward from
No. 3 main bearing.

Cylinder head components
The cylinder head components are described below:

Cylinder head
The cylinder head is of aluminium construction. It is not possible to reface the cylinder head if it becomes worn or
damaged. An alloy camshaft carrier is bolted directly to the upper surface of the cylinder head. Two dowels are
included in the cylinder head upper face for correct location of the camshaft carrier.

The EU3 cylinder head has a single internal fuel rail for delivering fuel to the injectors and an external fuel pipe for
returning spill fuel back to the fuel connector block. Therefore, pre EU3 and EU3 model cylinder heads are not
interchangeable.

CAUTION: The cylinder head incorporates drillings for the fuel injection system, any contamination which
enters these drillings could cause engine running problems or injector failure. It is therefore, essential that
absolute cleanliness is maintained when carrying out work on the cylinder head.

ENGINE - TD5

12-1-22 DESCRIPTION AND OPERATION

The camshaft carrier and cylinder head assembly is attached to the cylinder block by twelve cylinder head retaining
bolts which pass through the camshaft carrier and the cylinder head to secure the assembly to the cylinder block.

CAUTION: The valve heads, tips of the injectors and glow plugs protrude below the face of the cylinder head
and will be damaged if the cylinder head is stored face down.

The camshaft is located between the cylinder head and the camshaft carrier, and the bearing journals are line bored
between the two components to form a matched pair.

CAUTION: Always fit plugs to open connections to prevent contamination.

The valve guides and valve seat inserts are sintered components which are interference fit to the cylinder head. The
cylinder head machining also provide the locations for the electronic unit injectors, glow plugs, hydraulic lash
adjusters, finger followers and low pressure fuel rail.

Cooling to the cylinder head is provided by coolant flow through a water jacket machined into the cylinder head.
Drillings through the block provide lubrication channels for pressurised oil supply to cylinder head components such
as the lash adjusters, finger followers, rocker arms and camshaft bearings.

A coolant outlet elbow is fitted to the front LH side of the cylinder head to allow flow of coolant from the cylinder head
back to the radiator. A metal gasket is used to seal the joint between the water outlet elbow and the cylinder head. A
coolant temperature sensor is located in a port in the side of the water outlet elbow for monitoring coolant temperature.

A stub pipe is connected at the front RH side of the cylinder block above the timing cover which connects a pipe to
supply oil to the vacuum pump. The timing chain tensioner adjuster is screwed in a thread in the cylinder head at a
location on the front RH side of the engine below the oil feed port for the vacuum pump.

An access hole for the camshaft gear is included at the front of the cylinder head which is sealed with a plastic plug
and rubber 'O'-ring. A press-fit core plug for the chain chest is located on the front face of the cylinder head.

A press-fit core plug for the cylinder head water jacket is located at the rear of the cylinder head and a threaded brass
plug for the water jacket is located on the LH side of the cylinder head beneath the exhaust manifold assembly.

ENGINE - TD5

DESCRIPTION AND OPERATION 12-1-23

Fuel connector block

A = Pre EU3 models, B = EU3 models

1 Fuel connector block assembly
2 Outlet stub pipe
3 Stub pipe – to fuel cooler
4 Fuel temperature sensor
5 Fuel pressure regulator
6 Spill fuel return connection (EU3 models only)

A cast and machined alloy fuel connector block assembly is located at the rear RH side of the cylinder head, attached
by three flanged bolts. A metal gasket is used to seal the faces between the fuel connector block and the cylinder
head, which must be replaced every time the fuel connector block is removed.

CAUTION: The cylinder head incorporates drillings for the fuel injection system, any contamination which
enters these drillings could cause engine running problems or injector failure. It is therefore, essential that
absolute cleanliness is maintained when carrying out work on the cylinder head.

CAUTION: The valve heads, tips of the injectors and glow plugs protrude below the face of the cylinder head
and will be damaged if the cylinder head is stored face down.

Camshaft carrier
The cast aluminium alloy camshaft carrier is bolted to the cylinder head by thirteen screws. The camshaft carrier and
cylinder head assembly is attached to the cylinder block by twelve cylinder head retaining bolts which pass through
the camshaft carrier and the cylinder head to secure the assembly to the cylinder block.

The carrier is machined together with the cylinder head to form a matched pair for carrying the camshaft.

Non-return valve
A non-return valve is located at the front, bottom LH side of the cylinder head. The non-return valve prevents oil from
draining from the lash adjusters and is an integral component within the cylinder head and is non-serviceable.

ENGINE - TD5

12-1-24 DESCRIPTION AND OPERATION

Camshaft
The camshaft is machined from cast steel and is located between the cylinder head and the camshaft carrier, and the
six bearing journals are line bored between the two components to form a matched pair. The machined camshaft has
15 lobes. Ten lobes operate the inlet and exhaust valves through hydraulic lash adjusters and finger followers which
are located below the camshaft. Five larger lobes activate the injector rockers which are located above the camshaft
on the rocker shaft and are used to generate fuel pressure in the EUI injectors.

The camshaft is sprocket driven via a duplex chain connected to the crankshaft sprocket at a speed ratio of 2:1. The
camshaft sprocket is fixed to the front end of the camshaft by three bolts.

Camshaft lubrication is splash and channel fed via pressurised oil flowing through galleries in the cylinder head.

Rocker shaft and Rocker Arms

A = Pre EU3 rocker arm, B = EU3 rocker arm

1 Rocker shaft
2 Rocker arm adjusting screw
3 Rocker arm
4 EUI pin and roller assembly
5 Roller pin retention slug

6 Camshaft lobe
7 Injector spring
8 Injector push-rod
9 Adjusting nut

The hollow rocker shaft is located in the camshaft carrier in six fixed mountings which sit above the camshaft. Six bolts
are used to lock the rocker shaft to the camshaft carrier. The front rocker shaft bearing has a ring dowel located at the
front rocker shaft mounting of the camshaft carrier for rocker shaft alignment. Two circlips hold each rocker arm in
position at the relevant positions on the rocker shaft.

The rocker shaft from a pre EU3 model must not be fitted to an EU3 engine. This is because the stroke of the
EU3 injector has increased which requires the rocker to articulate over a larger angle.

The camshaft end of each rocker arm features a roller which is free to rotate about a pin which passes through two
webs in the rocker arm, the roller pins are held in place by an interference fit retention slug passing through a hole in
the front web of each rocker arm.

To correctly function against the higher injection loads of the EU3 engine the geometry of the contact between the
injector pushrod and rocker arm adjusting screw has been modified. Both designs of adjusting screw are separately
available with the EU3 version being identified by an engraved dimple in the slotted end.

Rocker shaft and rocker arm lubrication is splash and channel fed via pressurised oil flowing through galleries in the
cylinder head and through the rocker shaft.