Lotus Evora - Maintenance

Page 4
Lotus Service Notes Section KJ
panel. A hose from the engine coolant outlet housing feeds the heat exchanger, with a return hose linking to
the heater return circuit. When the engine is cold, heat is transferred from the quickly warming coolant to the
engine oil, whilst at high engine temperatures, the temperature managed coolant acts to extact heat from the
hotter lubrication system.
Thermostat open circuit (normal running temperature):
At temperatures above 84°C (183°F), the thermostat fully opens the radiator circuit, and closes the by-
pass valve.
From the engine outlet housing at the rear of the engine, a pipe running through the left hand sill directs
coolant to the single front radiator, rubber mounted between the two longerons of the front subframe and angled
forwards at about 45 degrees. The a.c. condenser is mounted ahead of the radiator, to which it is secured by
brackets riveted to each sideframe of the radiator. Cooling air is admitted through the front clamshell intake
aperture, and exhausted upwards through ducts in the front clamshell ahead of the windscreen, with airflow
augmented when necessary by two electric fans, each with 7 curved blades, mounted on the rear face of the
radiator. The fans are housed in a plastic shroud which incorporates 12 load relief flaps designed to blow
open under ram airflow, and be sucked closed when the fans are operating, in order to maximise fan cooling
efficiency. The aluminium radiator core uses moulded plastic top and bottom tanks, with the top tank divided in
order to direct the incoming coolant downwards through the LH side, and then upwards through the RH side to
the outlet spout. A pipe through the RH sill returns coolant to the thermostat housing on the front of the engine,
within which coolant flows through the open thermostat and back into the water pump.
The heater, throttle body and oil/water heat exchanger circuits continue to operate as described above,
with a low flowrate through the radiator by-pass circuit.
Header tank
To ensure that the cooling system remains fully filled, whilst providing expansion space for the hot coolant
and to facilitate 'topping up' of the system, a translucent header tank is mounted at the LH rear of the engine
bay. The tank is connected into the cooling system via a hose which joins into the heater return hose, whilst
an air bleed hose from the radiator feed hose near the outlet housing, connects to the air space in the header
tank. A threaded, 108 kPa (15 psi) pressure cap is fitted to the neck of the tank.
Re-circulation pump
In order to control engine temperature in conditions of 'heat soak' after stopping a hot engine, an electric
re-circulation pump is fitted in the heater take off hose between the engine outlet and heater feed pipework.
The pump is enabled for a short period after engine shut down, and is energised under engine ECU control to
pump coolant through the heater circuit and limit the potential for localised boiling within the cylinder head. For
details of the pump control strategy, refer to sub-section KJ.5
KJ.2 - MAINTENANCE
The engine cooling system uses a header tank to ensure that the system remains completely filled, and
also to accommodate expansion of the coolant with increasing engine temperature. The tank is mounted at the
left hand rear of the engine bay, and is fitted with a 108 kPa (15 psi) pressure cap to raise the boiling point of
the coolant to over 120°C (250°F).
WARNING
• Do NOT attempt to remove the pressure cap from the header tank when the engine is warm as
serious scalding could result from boiling water and/or steam.
• Coolantishazardoustoyourhealthandmaybefatalifswallowed.
• Keepcoolantoutofreachofchildren.
• Coolantishazardoustoanimalsandmaybefatalifswallowed.Cleanupspilledcoolantanddo
not leave in open containers.
The level of coolant in the translucent header tank will rise as the engine warms up, and fall as it cools
down, and under normal circumstances it should not be necessary to add any coolant to the system between
scheduled services. If overfilled, the excess coolant will be expelled when the engine is warm. If underfilled,
overheating may result. When the engine is completely cold, and the car is standing on a completely level