Defender (1999-2002). Manual - part 22

ENGINE

DESCRIPTION AND OPERATION

The engine oil cooler assembly is located on the left hand side of the engine block behind the oil centrifuge and oil
filter. The housing is bolted to the engine block by seven bolts. A matrix is included in the oil cooler housing which
acts as a heat exchanger. Coolant flow circulates through the oil cooler housing under pressure from the coolant
pump and distributes the flow evenly around the matrix fins and then along the block into three core holes for
cylinder cooling. Coolant enters the oil cooler through a pipe with a rubber hose extension at the rear side of the
engine. The coolant hose is attached to the stub pipe of the oil cooler by a spring clip.

Oil, drawn from the sump by the oil pump, passes through the oil cooler via the cylinder block. The flow of coolant
around the exterior surface of the oil cooler matrix cools a proportion of the engine oil flow as it passes through the
oil cooler.

The oil cooler is sealed to the cylinder block by a gasket which must be replaced every time the oil cooler housing
is removed.

ENGINE

DESCRIPTION AND OPERATION

Oil filters
The Td5 engine features two types of oil filter; the main filter is a standard disposable cartridge-type full flow oil
filter which is augmented with a by-pass centrifuge filter used to filter out particulate matter having a smaller
diameter smaller than 15 micron but greater than 3 micron.

1. Centre spindle
2. Spindle oil holes (2 off)
3. Centrifuge filter housing
4. Centrifuge filter drain pipe
5. Port - centrifuge filter drain pipe to sump

6. Filter rotor
7. Internal seal
8. Cover
9. Cover screws (2 off)

The centrifuge filter is located on the left hand side of the engine block by the exhaust manifold and is housed in a
pot which is bolted to the oil cooler housing by means of three bolts. The pot contains a rotor located on a central
spindle which spins at up to 15,000 rev/min when oil is flowing through the unit under pressure. The rotor contains
two fine holes drilled at obtuse angles which cause the rotor to spin about the centre spindle when high pressure
oil is passing through it. The inner surface of the rotor captures carbon deposits and small particulate matter as it
is thrown outwards under centrifugal force to form a sludge on the inner walls of the rotor. The unit is able to trap
very fine impurities that build up in the oil that would be too small to filter using the normal paper-element type
full-flow filters alone.

ENGINE

DESCRIPTION AND OPERATION

Full flow filter

Approximately 10% of the total oil flow enters the centrifuge pot through a side port in the pot casting which is
mated to an outlet port at the lower side of the oil cooler housing. A rubber ’O’ ring sits in a recess around the oil
cooler port which seals the faces between the centrifuge pot and oil cooler port, and it must be replaced every
time the centrifuge assembly is removed. Oil leaves the centrifuge pot through a drain tube which is attached to
the base of the pot by means of two fixing screws. The lower end of the drain tube returns oil to the sump and is
fixed to the sump by means of two screws. Gaskets are included at the port interfaces between the oil drain tube
and the centrifuge pot and the oil drain tube and sump return port; these gaskets must be replaced every time the
oil drain tube is removed.

The centrifuge cover is fixed to the pot by two screws and is sealed by an ’O’ ring.

1. Full-flow filter housing
2. Thermostat
3. Roll-pin

4. Port - feed line to turbocharger
5. Outlet port from full-flow filter - higher than 74

6. Inlet port to full-flow filter
7. Outlet port from full-flow filter - lower than 74

The main filter is a conventional full flow cartridge type filter containing a paper element able to trap particles
greater than 15 micron (0.015 mm) in diameter.

The cartridge is screwed to an adaptor casting by way of a hollow brass threaded insert which connects the filter
outlet port to the adaptor casting. A sealing ring seals the union between the oil filter cartridge and the adaptor
casting.

ENGINE

DESCRIPTION AND OPERATION

Oil filter housing thermostat

1. Circlip
2. Thermostat end cap
3. Oil seal
4. Thermostatic valve

5. Return spring
6. Oil filter housing
7. Threaded insert

The oil filter housing contains a thermostatically controlled valve to control the direction and proportion of oil flow
through the oil cooler matrix. When the oil temperature is cool, the centre spindle of the thermostatic element is
compressed. In this condition the valve completely seals the passage to the turbocharger feed tapping and flow is
directed through the oil filter adaptor housing, passing from the outlet of the full-flow filter to the cylinder block via
the rear oil return gallery in the oil cooler housing. A proportion of the oil flow from the right hand filter outlet port is
passed through to the oil cooler matrix to supply the turbocharger oil feed line.

When the oil temperature rises, the heated wax in the thermostat causes the thermostat centre spindle to rise and
push against the housing end cap, compressing the valve spring further and so opening the valve. In this
condition, oil flow from the outlet side of the full-flow filter is allowed to pass directly to the turbocharger oil feed
line and reverses the flow through the oil cooler matrix, which now delivers a proportion of cooled oil flow to the
cylinder block via the outlet port at the right hand side of the oil cooler housing.

The filter canister contains a by-pass valve which opens when the engine is cold or if the filter becomes blocked.
The by-pass valve opens when a pressure drop of greater than 1.6 kg/cm

(157 kPa, 23 lbf/in

) is experienced.

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