Lotus Elise S1 Service Notes page 338

I Lotus Service Notes Section JH
KF.1 - G E N E R A L D E S C R I P T I O N
The engine cooling system comprises an engine driven water pump, a front mounted radiator with elec-
tric cooling fan, and associated pipework and controls.
The centrifugal water pump is mounted on the front face of the cylinder block, and is driven by the
camshaft toothed belt. Water is discharged from the pump into the front of the cylinder block, around the
cylinder liners and up into the cylinder head, before exiting the engine via an outlet elbow at the left hand rear
of the head. From the outlet elbow, there are three routes through which water may flow:
Radiator circuit; The larger of the two spouts on the outlet elbow is connected via an alloy pipe
running through the chassis right hand side rail, to the front mounted radiator. Water returns from
the radiator via a pipe in the chassis left hand side rail to the engine bay. One of a pair of steel tube
water rails then directs this water around the back and the right hand side of the engine to a plastic bodied
thermostat housing fixed to the back of the water pump.
Heater circuit; A take-off for the heater is provided in the radiator feed circuit at the right hand front of the
engine bay, from where it is routed through an alloy pipe fixed to the outside face of the R H chassis side
rail, to the heater matrix mounted between the front chassis rails. Water returns from the heater via a
pipe routed outside the LH chassis side rail, and a second steel tube engine bay water rail, to the water
pump side of the thermostat housing.
Radiator by-pass circuit; The smaller of the two spouts on the cylinder head outlet elbow connects
directly with the heater return pipework. When the thermostat is closed, the radiator return circuit is shut
off, so that water is forced to flow through the heater and by-pass circuits, thus ensuring optimum heater
performance.
The header tank is mounted at the left hand front of the engine bay, with a hose from its underside
connecting with the heater return rail near the thermostat housing. An air bleed hose connects the header tank
air space with the radiator by-pass circuit and a cylinder head spigot at the front end of the inlet manifold. T h e
tank is fitted with a 110 kPa (15 lb/in
2
) pressure cap to raise the boiling point of the coolant to over 120°C.
The engine cooling radiator is of aluminium construction with plastic end tanks and is horizontally mounted
at the front of the vehicle, on top of the glass fibre composite 'crash structure" which also serves as a duct to
direct airflow from the body nose air intake, to the underside of the radiator. A single ?? mm diameter electric
cooling fan is fitted to the underside of the radiator to supplement, when required, the ram air flow, and a
composite duct directs air exhausting from the top of the radiator through outlets incorporated into the front
bonnet. Separate coolant temperature sensors for the engine management system (which also controls the
radiator fan), and the temperature gauge are fitted in the cylinder head outlet elbow.
KF.2 - M A I N T E N A N C E
Under normal operating
conditions, the engine cooling
system, being a closed circuit,
should not require any topping up
between services. As a precau-
tion however, every week, the
level of coolant in the engine
cooling header tank should be
c h e c k e d . T h e t r a n s l u s c e n t
header tank is marked with both
cold and hot level indicators. The
level of coolant will rise as the
engine warms up and the cool-
ant expands, and will fall again
as it cools down.
Coolant header tank
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