Radiator Fan & Re-Circ. Pump Control; Radiator Feed & Return Pipes; Cooling Fans Control; Heat Soak - Lotus Evora Service Notes

Lotus Service Notes
6. To avoid the requirement to recover the refrigerant, provide alternative support before releasing
the 4 fixings securing the a.c. condenser to the radiator; ensure that the a.c. pipes and unions are not
stressed.
7. Release the two brackets securing the top of the radiator to the subframe and ease the spigots on the
bottom tank from its mounting grommets. Withdraw the radiator and fan motor assemblies from the car.
8. Refit in reverse order to removal, and refill the cooling system (see sub-section KJ.3).
KJ.5 - RADIATOR FAN & RE-CIRC. PUMP CONTROL
The two cooling fans are fitted on the top side of the radiator/condenser package, and the coolant re-
circulation pump is mounted at the top left hand rear of the engine, plumbed into the heater feed circuit. Both
the fans and pump are controlled by the engine management ECU using data provided by the engine coolant
temperature sensor and a.c. pressure sensor.

Cooling Fans Control

The cooling fans are switched as a pair, and will operate at half speed (connected in series) when cool-
ant temperature reaches 98°C on rise (94°C with a.c. on), and switch off at 96°C on fall (92°C with a.c. on). If
coolant temperature rises to 105°C (96°C with a.c. on), the fans will switch to full speed (connected in parallel),
reverting to half speed on fall at 98°C (94°C with a.c. on).
Note that the temperatures displayed on the instrument panel may differ from the programmed values
described above due to damping lag.
The fans are also activated by signals received from the air conditioning pressure sensor; the fans will run
at low speed for pressures between 13 - 18 bar, and at high speed for pressures over 18 bar.
Certain types of ECU detected engine fault will also cause the fans to be activated as an engine protection
measure. If the ECU receives a coolant temperature sensor signal voltage outside of the acceptable range, a
default setting equating to 60°C will be substituted, and the cooling fans will run at half speed.
Re-circulation Pump
A coolant re-circulation electric pump is mounted on a bracket fixed to the underside of the intake airbox,
and is plumbed into the heater supply line close to the coolant outlet housing at the LH end of the engine. When
energised, the pump circulates coolant through the heater system, drawing coolant from the cylinder head, and
pumping it through the heater matrix and back to the engine.

Heat Soak

After ignition switch off, the ECU remains live for a minimum period of 1 minute for coolant temperatures
below 75°C (at time of switch off), extending progressively to a maximum period of 10 minutes for temperatures
over 90°C. If, during this period, the coolant temperature exceeds 110°C, the re-circ. pump will be activated
and will run for a maximum period of 6 minutes, or until the coolant temperature falls to 50°C.
If, during the ECU live period the coolant temperature rises to 120°C, the cooling fans will run at slow speed
in addition to the re-circ. pump, for a maximum period of 2 minutes, or until the temperature falls to 70°C.
Defrost Enhancement
In order to speed windscreen defrosting/demisting, when coolant temperature is between 2°C and 60°C,
the re-circ. pump will be activated to boost coolant circulation through the heater matrix, commencing 10 sec-
onds after engine start up. The pump will continue to run until 30 seconds after either 1400 rpm is exceeded,
or the coolant reaches 60°C.
KJ.6 - RADIATOR FEED & RETURN PIPES
For both the feed and return circuits between the engine and radiator, two alloy pipes are utilised, one
routed together with other pipework, along the outside of the chassis main siderail (feed on left, return on right),
within the composite body sill moulding, and one pipe over the wheelarch area to link the front end of the sill pipe
with the radiator. No joints are incorporated in the sill sections, where the pipes are supported in foam blocks
Page 7
Section KJ