1995 LAND ROVER DISCOVERY Service Repair Manual

ENGINE
12
DESCRIPTION AND OPERATION

ENGINE
DESCRIPTION AND OPERATION13
TIMING BELT AND FRONT COVER
1.Timing belt
2.Gasket
3.Access plate
4.Bolt - access plate
5.Timing belt front cover6.Bolts - timing belt front cover
7.Wading plug
8.Oil seal
9.Crankshaft pulley
10.Pulley bolt

ENGINE
14
DESCRIPTION AND OPERATION

ENGINE
DESCRIPTION AND OPERATION15
OPERATION
The 300 TDi is a 4 cylinder, water cooled,
turbocharged diesel engine with a capacity of 2.5
litres.
The cast iron cylinder block is integral with the
crankcase and incorporates direct bored cylinders.
The crankshaft is carried in 5 main bearings,
end-float being controlled by thrust washers which
are positioned on both sides of the centre main
bearing.
The flywheel/drive plate housing is an aluminium
alloy casting secured to the rear of the cylinder
block, it also forms the mounting for the starter
motor. A plugged aperture in the housing allows
access for the insertion of the timing pin.
The aluminium alloy cylinder head carries a
conventional rocker shaft and rockers, operating 2
valves per cylinder via camshaft followers and push
rods from a single camshaft, supported in the
cylinder block by 4 bearings and driven by a gear
and toothed belt from the crankshaft. A lobe formed
between the 2 inner bearing journals provides drive
for the fuel lift pump and another lobe, between the 2
drive end journals provides drive for the brake servo
pump. Camshaft end-float is controlled by a thrust
plate bolted to the cylinder block.
Graphite coated, aluminium alloy pistons are fitted
with 2 compression and an oil control ring and are
secured to the connecting rods by semi-floating
gudgeon pins which are an interference fit in the
small end bush. A swirl chamber is incorporated in
the piston crown to facilitate combustion.
The timing case consists of cast aluminium alloy
front and rear covers which house the oil pump,
crankshaft and camshaft front oil seals and which
also carry the fuel injection pump and drive belt idler
pulley. Housed within the timing case housing is the
crankshaft gear which provides drive for the
camshaft and fuel injection pump gears via a rubber
toothed belt.

ENGINE
16
DESCRIPTION AND OPERATION

ENGINE
DESCRIPTION AND OPERATION17
Lubrication
The engine lubrication system is of the wet sump
type, oil pressure being provided by the rotor type oil
pump (1) driven directly by the crankshaft.
Oil is drawn from the sump (2) through the strainer
(3), suction pipe (4) and passes through internal
drillings in the cylinder block to an external, full flow
filter (5). Further drillings feed oil to the cylinder
block main oil gallery (6) which, in turn, supplies the
crankshaft main bearings (7). Cross drillings in the
crankshaft carry oil to the connecting rod big-end
bearings (8). The camshaft bearings (9) are supplied
with oil from the main oil gallery.
An internal oilway from the camshaft front bearing
connects the cylinder block to the cylinder head and
feeds oil to the rocker shaft assembly (10),
lubricating the valves and springs.
The pistons, gudgeon pins and small end bushes
are lubricated and cooled by oil jets (11) which are
supplied from the main oil gallery via relief valves
which allow the oil to flow at a pre-determined
pressure.
Oil pressure is controlled by a pressure relief valve
(12) incorporated in the timing case housing
together with the oil pump. The valve allows excess
oil to be recirculated back into the oil feed gallery.
The rotor type oil pump is driven by 2 flats machined
on the front of the crankshaft.
Oil cooling is maintained by an oil cooler which is
integral with the radiator and linked to adaptors on
the oil filter head by pre-formed feed and return
hoses. A thermostatic valve in the filter head allows
oil to flow to the cooler when it reaches a
pre-determined temperature.

ENGINE
18
DESCRIPTION AND OPERATION
Crankcase ventilation system
A breather cyclone unit (1), fitted to the right hand
side of the rocker cover controls the rate at which air
is purged from the sump, via a hose (2) from the
camshaft side cover to the rocker cover and extractsoil from the gaseous atmosphere. The oil then drains
back to the sump through a hose and flanged pipe
connection (3). The residues are drained-off from
the top of the cyclone breather and pass through a
hose (4) into the engine via the turbocharger where
they are burned in the combustion chamber.

ENGINE
OVERHAUL1
TIMING BELT, TENSIONER AND GEARS
Timing belt - remove
1.Position toolLRT-12-080to crankshaft pulley,
retain with 4 bolts.
2.Restrain crankshaft using toolLRT-12-080
and remove crankshaft pulley flange head bolt.
NOTE: Bolt and washer fitted to early
engines.
3.Remove toolLRT-12-080 .
4.Position toolLRT-12-049and thrust button,
part of toolLRT-12-031to crankshaft pulley,
remove pulley, recover Woodruff key.
5.Using sequence shown, progressively slacken
then remove 14 bolts securing timing belt front
cover.