3•2 Cooling, heating and ventilation systems
Trionic engine management system temperature sensor
General information
1 The cooling system is of pressurised type,
comprising a water pump driven by the
auxiliary drivebelt, a crossflow radiator,
electric cooling fan, a thermostat, heater
matrix, and all associated hoses. The
expansion tank is located on the right-hand
side of the engine compartment.
2 The system functions as follows. Cold
coolant in the bottom of the radiator passes
through the bottom hose to the water pump,
where it is pumped around the cylinder block
and head passages. After cooling the cylinder
bores, combustion surfaces and valve seats,
the coolant reaches the underside of the
thermostat, which is initially closed. The
coolant passes through the heater, and is
returned via the cylinder block to the water
pump.
3 When the engine is cold, the coolant
circulates only through the cylinder block,
cylinder head, throttle housing (Trionic system)
and heater. When the coolant reaches a
predetermined temperature, the thermostat
opens, and the coolant passes through the top
hose to the radiator. As the coolant circulates
through the radiator, it is cooled by the inrush
of air when the car is in forward motion, and
also by the action of the electric cooling fan
when necessary. Upon reaching the bottom of
the radiator, the coolant has now cooled, and
the cycle is repeated.
4 When the engine is at normal operating
temperature, the coolant expands, and some
of it is displaced into the expansion tank.
Coolant collects in the tank, and is returned to
the radiator when the system cools.
5 The electric cooling fan mounted on the rear
of the radiator is controlled by a thermostatic
switch. At a predetermined coolant
temperature, the switch/sensor actuates the
fan.
Precautions
Warning: Do not attempt to
remove the expansion tank filler
cap, or to disturb any part of the
cooling system, while the engine
is hot, as there is a high risk of scalding. If
the expansion tank filler cap must be
removed before the engine and radiator
have fully cooled (even though this is not
recommended), the pressure in the cooling
system must first be relieved. Cover the
cap with a thick layer of cloth, to avoid
scalding, and slowly unscrew the filler cap
until a hissing sound is heard. When the
hissing has stopped, indicating that the
pressure has reduced, slowly unscrew the
filler cap until it can be removed; if more
hissing sounds are heard, wait until they
have stopped before unscrewing the cap
completely. At all times, keep well away
from the filler cap opening, and protect
your hands.
Warning: Do not allow antifreeze
to come into contact with your
. skin, or with the painted surfaces
of the vehicle. Rinse off spills
immediately, with plenty of water. Never
leave antifreeze lying around in an open
container, or in a puddle in the driveway or
on the garage floor. Children and pets are
attracted by its sweet smell, but antifreeze
can be fatal if ingested.
Warning: If the engine is hot, the
electric cooling fan may start
rotating even if the engine is not
running. Be careful to keep your
hands, hair, and any loose clothing well
clear when working in the engine
compartment.
Warning: Refer to Section 10 for
precautions to be observed when
working on models with air
conditioning.
1 The number, routing and pattern of hoses
will vary according to model, but the same
basic procedure applies. Before commencing
work, make sure that the new hoses are to
hand, along with new hose clips if needed. It is
good practice to renew the hose clips at the
same time as the hoses.
2 Drain the cooling system, as described in
Chapter 1, saving the coolant if it is fit for re-
use. Squirt a little penetrating oil onto the hose
clips if they are corroded.
3 Unscrew the clips and release the hose
clips from the hose concerned.
4 Unclip any wires, cables or other hoses
which may be attached to the hose being
removed. Make notes for reference when
reassembling if necessary. The hoses can be
removed with relative ease when new - on an
older vehicle, they may have stuck.
5 If a hose proves stubborn, try to release it
by rotating it on its unions before attempting
to work it off. Gently prise the end of the hose
with a blunt instrument (such as a flat-bladed
screwdriver), but do not apply too much force,
and take care not to damage the pipe stubs or
hoses. Note in particular that the radiator hose
unions are fragile; do not use excessive force
when attempting to remove the hoses.
If all else fails, cut hoses with
a sharp knife, then slit them
so that they can be peeled off
in two pieces. While
expensive, this is preferable to buying a
new radiator. Check first, however, that
new hoses are readily available.
6 Before fitting the new hose, smear the stubs
with washing-up liquid or a suitable rubber
lubricant to aid fitting. Do not use oil or grease,
which may attack the rubber.
7 Fit the hose clips over the ends of the hose,
Resistance:
At -30°C 20 000 to 30 000 ohms
At -10°C 7000 to 11 400 ohms
At 20°C 2100 to 2900 ohms
At 40°C 1000 to 1300 ohms
At 60°C 565 to 670 ohms
At 80°C 295 to 365 ohms
At 90°C 24 to 26 ohms
At 110°C 14 to 16 ohms
Torque wrench settings Nm
Automatic transmission fluid hose to radiator 25
Coolant temperature sensor (Trionic system) 13
Thermostat housing:
B2O2/B2O4 engines 18
B234 engine 22
Water pump 22
Water pump pulley 8