Peugeot 405. Manual - part 27

the removal procedure. Twist the end of the
hose fully clockwise to ensure that the
retaining clips are engaged with the lugs on
the radiator stub.

3

Radiator - removal, inspection
and refitting

3

Removal

1 Disconnect the battery negative lead.
2 Where applicable, disconnect the wiring
from the coolant level sensor, mounted in the
right-hand side of the radiator.
3 Similarly, where applicable disconnect the
wiring from the cooling fan switch, mounted
left-hand side of the radiator.
4 Drain the cooling system as described in
Chapter 1.
5 Where applicable, depress the securing

clip, and release the air inlet tube from the
body front panel, above the radiator (see
illustrations).
6 Where applicable, disconnect the wiring
plug and the vacuum hose from the MAP
sensor, located above the radiator, then
unscrew the two bolts securing the sensor
mounting bracket to the body front panel, and
remove the sensor.
7 Disconnect the upper radiator hose from
the left-hand end of the radiator, with
reference to Section 2.
8 It is now necessary to disconnect the lower
radiator hose(s) from the right-hand side of
the radiator. On some models, particularly
those where conventional hose clips are used,
this is a straightforward task. On other models
(where bayonet connectors are used on a
large-capacity radiator), it is impossible to
gain access to the lower radiator hose
connections without removing the body front
panel assembly, as described in Chapter 11
(see illustration).
9 Once all the radiator hoses have been
disconnected, proceed as follows.
10 If not already done, working at the top of
the radiator, release the two securing clips,
and tilt the radiator back towards the engine
(see illustration).
11 Lift the radiator from the engine
compartment 

(see illustration).

Inspection

12 If the radiator has been removed due to
suspected blockage, reverse-flush it as
described in Chapter 1. Clean dirt and debris
from the radiator fins, using an air line (in
which case, wear eye protection) or a soft

brush. Be careful, as the fins are sharp, and
easily damaged.
13 If necessary, a radiator specialist can
perform a “flow test” on the radiator, to
establish whether an internal blockage exists.
14 A leaking radiator must be referred to a
specialist for permanent repair. Do not
attempt to weld or solder a leaking radiator,
as damage to the plastic components may
result.
15 In an emergency, minor leaks from the
radiator can be cured by using a suitable
radiator sealant, in accordance with its
manufacturer’s instructions, with the radiator
in situ.
16 If the radiator is to be sent for repair or
renewed, remove all hoses, and the cooling
fan switch (where fitted).
17 Inspect the condition of the radiator
mounting rubbers, and renew them if
necessary.

Refitting

18 Refitting is a reversal of removal, bearing
in mind the following points:

a) Ensure that the lower lugs on the radiator

are correctly engaged with the mounting
rubbers in the body panel.

b) Reconnect the hoses with reference to

Section 2, using new O-rings where
applicable.

c) Where applicable, refit the body front

panel assembly, referring to Chapter 11.

d) On completion, refill the cooling system

as described in Chapter 1.

4

Thermostat - removal, testing
and refitting

3

Removal

Note: A new sealing ring may be required on
refitting.
1 Disconnect the battery negative lead.
2 Drain the cooling system as described in
Chapter 1.
3 Where necessary, release any relevant
wiring and hoses from the retaining clips, and
position clear of the thermostat housing to
improve access. On some models, access is

Cooling, heating and ventilation systems  3•3

3.5b  . . . and withdraw the air intake tube

3.11  Lifting out the radiator

3.10  Releasing a radiator 

upper securing clip

3.8  Lower radiator hose connections

viewed with body front panel removed

3.5a  Depress the securing clip . . .

2.12b  Recover the O-ring (arrowed) from

the end of the hose connector

3

also improved if the air cleaner ducting is
removed is removed (see Chapter 4).
4 Unscrew the retaining bolts, and carefully
withdraw the thermostat housing cover to
expose the thermostat. Take care not to strain
the coolant hose(s) connected to the cover
(see illustrations).
5 Lift the thermostat from the housing, and
recover the sealing ring(s) (see illustration).

Testing

6 A rough test of the thermostat may be
made by suspending it with a piece of string in
a container full of water. Heat the water to
bring it to the boil - the thermostat must open
by the time the water boils. If not, renew it.
7 If a thermometer is available, the precise
opening temperature of the thermostat may
be determined; compare with the figures
given in the Specifications. The opening
temperature is also marked on the thermostat.
8 A thermostat which fails to close as the
water cools must also be renewed.

Refitting

9 Refitting is a reversal of removal, bearing in
mind the following points:

a) Examine the sealing ring(s) for signs of

damage or deterioration, and if necessary,
renew.

b) Ensure that the thermostat is fitted the

correct way round, with the spring(s)
facing into the housing.

c) On completion, refill the cooling system

as described in Chapter 1.

5

Electric cooling fan(s) -
testing, removal and refitting

4

Testing

1 Current supply to the cooling fan(s) is via
the ignition switch (see Chapter 10) and a fuse
(see Chapter 12). The circuit is completed by
the cooling fan thermostatic switch, which (on
most models) is mounted in the radiator. On
models with air conditioning, the cooling fans
are controlled by the “Bitron” sensor - see
Section 6.
2 If a fan does not appear to work, run the

engine until normal operating temperature is
reached, then allow it to idle. The fan should
cut in within a few minutes (before the
temperature gauge needle enters the red
section, or before the coolant temperature
warning light comes on). If not, switch off the
ignition and disconnect the wiring plug from
the cooling fan switch. Bridge the two
contacts in the wiring plug using a length of
spare wire, and switch on the ignition. If the
fan now operates, the switch is probably
faulty, and should be renewed.
3 If the fan still fails to operate, check that
battery voltage is available at the feed wire to
the switch; if not, then there is a fault in the
feed wire (possibly due to a fault in the fan
motor, or a blown fuse). If there is no problem
with the feed, check that there is continuity
between the switch earth terminal and a good
earth point on the body; if not, then the earth
connection is faulty, and must be re-made.
4 If the switch and the wiring are in good
condition, the fault must lie in the motor itself.
The motor can be checked by disconnecting it
from the wiring loom, and connecting a 12-
volt supply directly to it.

Removal

5 Remove the radiator (see Section 3).
6 Remove the front grille panel (Chapter 11).
7 Working behind the fan blades, unscrew
the three motor securing bolts, and withdraw
the motor/fan assembly forwards from the
shroud (see illustration). The plug on the
motor will be released from the wiring
connector as the motor is pulled forwards.

Refitting

8 Refitting is a reversal of removal, but refit
the radiator with reference to Section 3.

6

Cooling system electrical
switches and sensors -
testing, removal and refitting

2

Electric cooling fan thermostatic
switch - models without air
conditioning

Testing

1 Testing of the switch is described in
Section 5, as part of the electric cooling fan
test procedure.

Removal

2 The switch is located in the left-hand side
of the radiator. The engine and radiator should
be cold before removing the switch.
3 Disconnect the battery negative lead.
4 Partially drain the cooling system to just
below the level of the switch (see Chapter 1).
Alternatively, have ready a suitable bung to
plug the switch aperture in the radiator when
the switch is removed. If this method is used,
take great care not to damage the radiator,
and do not use anything which will allow
foreign matter to enter the radiator.
5 Disconnect the wiring plug from the switch.
6 Carefully unscrew the switch from the
radiator, and recover the sealing ring. If the
system has not been drained, plug the switch
aperture to prevent further coolant loss.

Refitting

7 Refitting is a reversal of removal, using a
new sealing ring. Tighten the switch, and refill
(or top-up) the cooling system (see Chapter 1).
8 On completion, start the engine and run it
until it reaches normal operating temperature.
Continue to run the engine, and check that the
cooling fan cuts in and out correctly.

Electric cooling fan thermostatic
switch - models with air
conditioning

9 On most models fitted with air conditioning,
the cooling fans are controlled by the “Bitron”
sensor. This is located in the thermostat

3•4 Cooling, heating and ventilation systems

4.4a  Thermostat housing cover retaining

bolts (arrowed) - 1.4 litre engine

4.5  Removing the sealing ring from the

thermostat flange

5.7  Fan motor securing bolts (arrowed) -

viewed from rear (grille panel side)

4.4b  Thermostat housing cover (arrowed)

- 2.0 litre engine

housing, and is described in more detail later
in this Section.
10 On some later models with air
conditioning, the cooling fan(s) is/are
controlled by a switch mounted in the
radiator, as described previously for models
without air conditioning. It will be self-evident
which type of switch is used. If no switch is
fitted to the radiator, the “Bitron” sensor is
used to control the fan(s).

Coolant temperature gauge/
temperature warning light
sender

Testing

11 The coolant temperature gauge/warning
light sender is screwed into the thermostat
housing.
12 The temperature gauge (where fitted) is
fed with a stabilised voltage from the
instrument panel feed (via the ignition switch
and a fuse). The gauge earth is controlled by
the sender. The sender contains a thermistor -
an electronic component whose electrical
resistance decreases at a predetermined rate
as its temperature rises. When the coolant is
cold, the sender resistance is high, current
flow through the gauge is reduced, and the
gauge needle points towards the blue (cold)
end of the scale. As the coolant temperature
rises and the sender resistance falls, current
flow increases, and the gauge needle moves
towards the upper end of the scale. If the
sender is faulty, it must be renewed.
13 On models with a temperature warning
light, the light is fed with a voltage from the
instrument panel. The light earth is controlled
by the sender. The sender is effectively a
switch, which operates at a predetermined
temperature to earth the light and complete
the circuit. If the light is fitted in addition to a
gauge, the senders for the gauge and light are
incorporated in a single unit, with two wires,
one each for the light and gauge earths. On
models with air conditioning, the light is
operated via the “Bitron” sensor - see
paragraphs 19 to 21.
14 If the gauge develops a fault, first check
the other instruments; if they do not work at
all, check the instrument panel electrical feed.
If the readings are erratic, there may be a fault
in the voltage stabiliser, which will necessitate
renewal of the stabiliser (the stabiliser is
integral with the instrument panel printed
circuit board - see Chapter 12). If the fault lies
in the temperature gauge alone, check it as
follows.
15 If the gauge needle remains at the “cold”
end of the scale when the engine is hot,
disconnect the sender wiring plug, and earth
the relevant wire to the cylinder head. If the
needle then deflects when the ignition is
switched on, the sender unit is proved faulty,
and should be renewed. If the needle still
does not move, remove the instrument panel
(Chapter 12) and check the continuity of the
wire between the sender unit and the gauge,

and the feed to the gauge unit. If continuity is
shown, and the fault still exists, then the
gauge is faulty, and the gauge unit should be
renewed.
16 If the gauge needle remains at the “hot”
end of the scale when the engine is cold,
disconnect the sender wire. If the needle then
returns to the “cold” end of the scale when
the ignition is switched on, the sender unit is
proved faulty, and should be renewed. If the
needle still does not move, check the
remainder of the circuit as described
previously.
17 The same basic principles apply to testing
the warning light. The light should illuminate
when the relevant sender wire is earthed.

Removal and refitting

18 The procedure is similar to that described
previously in this Section for the electric
cooling fan thermostatic switch. On some
models, access to the switch is very poor, and
other components may need to be removed
before the sender unit can be reached.

“Bitron” temperature sensor -
models with air conditioning

Testing

19 The sensor forms part of the air
conditioning “Bitron” control system (see
Section 11). Testing of the sensor should be
entrusted to a Peugeot dealer.

Removal and refitting

20 The “Bitron” temperature sensor is
screwed into the thermostat housing, which is
bolted onto the left-hand end of the cylinder
head.
21 The procedure is similar to that described
previously in this Section for the electric
cooling fan thermostatic switch. On some
models, access to the switch is very poor, and
other components may need to be removed
before the sender unit can be reached.

Coolant temperature sensor -
fuel injection models

Testing

22 The fuel injection system coolant
temperature sensor is screwed into the
thermostat housing, which is bolted onto the
left-hand end of the cylinder head.
23 The sensor is a thermistor (see paragraph
12). The fuel injection/engine management
electronic control unit (ECU) supplies the
sensor with a set voltage and then, by
measuring the current flowing in the sensor
circuit, it determines the engine’s
temperature. This information is then used, in
conjunction with other inputs, to control the
injector opening time (pulse width). On some
models, the idle speed and/or ignition timing
settings are also temperature-dependent.
24 If the sensor circuit should fail to provide
adequate information, the ECU’s back-up
facility will override the sensor signal. In this
event, the ECU assumes a predetermined
setting which will allow the fuel

injection/engine management system to run,
albeit at reduced efficiency. When this occurs,
the warning light on the instrument panel will
come on, and the advice of a Peugeot dealer
should be sought. The sensor itself can only
be tested using special Peugeot diagnostic
equipment. Do not attempt to test the circuit
using any other equipment, as there is a high
risk of damaging the ECU.

Removal and refitting

25 The procedure is similar to that described
previously in this Section for the electric
cooling fan thermostatic switch. On some
models, access to the switch is very poor, and
certain components may need to be removed
before the sensor can be reached.

7

Coolant pump - 
removal and refitting

4

Note: A new pump gasket or O-ring (as
applicable) will be required on refitting.

Removal

1 The coolant pump is driven by the timing
belt, and is bolted to the cylinder block at the
timing belt end of the engine. Note that on 1.4
litre aluminium cylinder block engines, the
coolant pump is bolted to a separate housing
which is in turn bolted to the side of the
cylinder block.
2 Drain the cooling system as described in
Chapter 1.
3 Remove the timing belt as described in
Chapter 2.
4 Where necessary, for access to the coolant
pump, remove the timing belt tensioner
and/or the rear timing belt cover as described
in Chapter 2.
5 On 1.4 litre engines, support the engine by
placing a trolley jack and interposed block of
wood under the sump, then remove the upper
engine mounting as described in Chapter 2.
6 Remove the securing bolts, and withdraw
the pump from the cylinder block (access is
most easily obtained from under the wheel
arch). Recover the gasket or the O-ring, as
applicable (see illustrations).
7 On 1.4 litre aluminium cylinder block
engines, if desired, the pump impeller housing
can be removed from the rear of the coolant
pump housing. Access is most easily
obtained from underneath the vehicle (it may
be necessary to remove the exhaust heat
shield). Disconnect the coolant hoses from
the impeller housing (be prepared for coolant
spillage), then remove the securing bolts and
withdraw the impeller housing. Again, recover
the O-ring.

Refitting

8 Ensure that all mating faces are clean.
9 Where applicable, refit the impeller housing
to the pump housing, using a new O-ring.
Reconnect the coolant hoses.

Cooling, heating and ventilation systems  3•5

3

10 Refit the pump using a new gasket or 
O-ring, as applicable.
11 Where applicable, refit the upper engine
mounting, with reference to Chapter 2, then
remove the jack from under the sump.
12 Where applicable refit the rear timing belt
cover and/or the timing belt tensioner with
reference to Chapter 2.
13 Refit the timing belt (refer to Chapter 2).
14 Refill the cooling system (see Chapter 1).

8

Heating and ventilation
system - general information

1 The heating/ventilation system consists of a
blower motor (housed behind the facia), face
level vents in the centre and at each end of
the facia, and air ducts to the front footwells.
2 Two types of system are fitted to the model
range. On basic specification models, the
heating/ventilation system is manually-
controlled. On higher specification models,
the system is electronically-controlled. The
components of both systems are identical,
with the exception of the control unit.
Additionally, on models with the electroni-
cally-controlled system, temperature sensors
and a thermostat are fitted to automatically
control the temperature of the air inside the
vehicle according to the position of the
temperature control knob.
3 The control unit is located in the facia, and
the controls operate flap valves to deflect and
mix the air flowing through the various parts of
the heating/ventilation system. The flap valves

are contained in the air distribution housing,
which acts as a central distribution unit,
passing air to the various ducts and vents.
4 Cold air enters the system through the grille
at the rear of the engine compartment. If
required, the airflow is boosted by the blower,
and then flows through the various ducts,
according to the settings of the controls. Stale
air is expelled through ducts at the rear of the
vehicle. If warm air is required, the cold air is
passed over the heater matrix, which is
heated by the engine coolant.
5 A recirculation switch enables the outside
air supply to be closed off, while the air inside
the vehicle is recirculated. This can be useful
to prevent unpleasant odours entering from
outside the vehicle, but should only be used
briefly, as the recirculated air inside the
vehicle will soon become stale.

9

Heater/ventilation
components - removal and
refitting

3

Heater/ventilation control unit -
models up to 1992

Removal

1 Disconnect the battery negative lead.
2 Where applicable, remove the radio/
cassette player as described in Chapter 12.
3 Move the steering column to its lowest
position.
4 Remove the lighting control stalk switch
(right-hand-drive models) or the wash/wipe

control stalk switch (left-hand-drive models),
as described in Chapter 12. Note that there is
no need to disconnect the switch wiring, but
the switch must be moved to allow clearance
for removal of the centre facia panel.
5 Unclip the trim panel from the lower edge of
the instrument panel to expose the upper
centre facia panel securing screw. Remove
the screw (see illustration).
6 Unclip the oddments tray from the front of
the facia centre panel.
7 Unclip the ashtray and remove it from the
facia.
8 Unscrew the five centre facia panel
securing screws exposed by removal of the
oddments tray and ashtray (see illustration).
9 Pull the centre facia panel forwards from
the facia, then reach behind the panel and
disconnect the wiring from the switches,
clock, and cigarette lighter, as applicable.
Note the locations of the wiring connectors to
ensure correct refitting, and remove the facia
panel.
10 Unscrew the four heater control unit
securing screws, then manipulate the unit
from the facia, and disconnect the control
cables and/or wiring plugs (see illustration).
The cables can be disconnected after
releasing the metal spring clips securing the
cable sheaths to the control unit.

Refitting

11 Refitting is a reversal of removal, but note
that the control cables must be reconnected
in the order shown (see illustration).
12 Refit the radio/cassette player with
reference to Chapter 12.

3•6 Cooling, heating and ventilation systems

7.6a  Withdraw the coolant pump . . .

7.6c  Removing the coolant pump (1.6 litre

engine) - shown with engine removed

9.10  Two heater control unit securing

screws (arrowed) - models up to 1992

9.8  Centre facia panel securing screws

(arrowed) - models up to 1992

9.5  Removing the upper centre facia panel

securing screw - models up to 1992

7.6b  . . . and recover the O-ring - 

1.4 litre engine shown