Lotus Elise / Lotus Exige. Instruction - part 64

                

  

Lotus Service Notes                                 Section KH

Page 1

ENGINE COOLING

SECTION KH

    Sub-Section   Page

General Description

KH.1

3

Maintenance

KH.2

3

Drain/Refill Procedure

KH.3

4

Radiator & Cooling Fan

KH.4

5

Radiator Fan Control

KH.5

7

Radiator Feed & Return Pipes

KH.6

8

Water Pump & Thermostat

See Section EH

Oil Coolers

KH.7

8

                

  

 Lotus Service Notes                                 Section KH

Page 2

Coolant Flow Circuits

Thermostat closed

Heater feed
pipe in sill

Throttle
body

Thermostat
housing

Heater matrix
in climate

        k74b

chamber

Heater
return

Heater return

pipe

pipe in sill

Heater feed from

Header tank

back of cylinder head

Radiator by-pass

Recirculation pump

Thermostat open

Radiator on

Radiator return pipe

crash

in chassis side rail

structure

Throttle body
thermostat

Heater matrix

        k74a

in climate
chamber

Return to
thermostat
housing

Radiator feed pipe
in chassis side rail

Heater feed from
back of cylinder head

Header tank

Recirculation pump

                

  

Lotus Service Notes                                 Section KH

Page 3

KH.1 - GENERAL DESCRIPTION

The engine cooling system comprises an engine driven water pump, a front mounted radiator with elec-

tric cooling fan(s), a header tank, re-circulation pump and associated ducting, pipework and controls.

The centrifugal water pump is mounted on the front face of the cylinder block, and is driven by the smooth

'back' side of the multi-rib auxiliary drive 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 spigot on
the rear of the head.
Radiator open circuit:

From the main outlet on the rear face of the cylinder head, a moulded hose connects with the main

radiator feed pipe which runs inside the left hand chassis side rail, before feeding the front mounted radiator.
The engine cooling radiator is of aluminium construction with plastic end tanks and is horizontally mounted 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.  Twin 100 mm diameter electric cooling fans are fitted to the
underside of the radiator to supplement, when required, the ram air flow, and a moulded deflector panels direct
air exhausting from the top of the radiator through outlet grilles in the front bonnet.  On cars equipped with air
conditioning, the condenser is sandwiched between the radiator and crash structure, with the cooling fans
attached to underside of the condenser.

The right hand, outlet spigot on the radiator feeds a return pipe routed down the inside of the chassis right

hand side rail, which is then connected to the thermostat housing on the left hand side of the block.  Coolant
flowing through the open thermostat enters the water pump to commence another circuit.
Heater circuit:

A second outlet spigot on the rear of the head is used to supply the heater circuit.  Water flows via a re-

circulation pump, into an aluminium pipe routed along the outside of the right hand chassis siderail, within the
composite sill member.  The front end of this pipe rises over the end of the scuttle, penetrates the plenum/
scuttle baffle panel, and connects to the heater matrix mounted in the chassis front climate chamber.  The
heater return circuit is similarly routed along the left hand side of the chassis, to join a steel heater return pipe
at the back of the cylinder head, and running beneath the inlet manifold to the underside of the thermostat
housing.

In conditions of 'heat soak', after stopping a hot engine, the re-circulation pump is energised under engine

ECU control to pump coolant through the heater circuit and limit the potential for localised boiling within the
cylinder head.
Radiator by-pass circuit:

When the thermostat is closed, the radiator return circuit is shut off, and coolant leaving the cylinder head

is forced to flow through a by-pass circuit which links the engine outlet hose to the header tank and then to the
heater return pipe.
Header tank:

The top RH spigot on the header tank is connected to an air bleed on the back of the cylinder head; the

top rear spigot to the engine outlet hose; and the bottom port to a hose joining the heater return pipe immedi-
ately before its termination at the thermostat housing.
Throttle body and oil/water heat exchanger

The throttle body is water heated to prevent icing, drawing a supply from the back of the cylinder head,

and returning via an in-line thermostat, into the heater return pipe.  On cars not fitted with front mounted air/oil
coolers, an oil/water heat exchanger is sandwiched between the oil filter and cylinder block.  Coolant is fed
from a water jacket spigot on the left hand side of the cylinder block into the exchanger, with the outlet pipe
connecting into the heater return pipe.

KH.2 - MAINTENANCE

Under normal operating conditions, the engine cooling system, being a closed circuit, should not require

any topping up between services.  As a precaution however, every week, the level of coolant in the engine
cooling header tank should be checked.  The header tank is mounted at the left hand side 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.  The tank is fitted with a 110 kPa (15 lb/in²) pressure cap to raise the boiling point of
the coolant to over 120°C. The transluscent header tank is marked with both cold and hot level indicators.  The

                

  

 Lotus Service Notes                                 Section KH

Page 4

level of coolant will rise as the engine warms up and the coolant expands, and will fall again as it cools down.

WARNING:  Do NOT remove the cap or bleed plug from the engine cooling header tank when the
engine is warm, as serious scalding could result from boiling water and/or steam.

When fully cold, the level of coolant should be up to the ‘cold’ mark moulded on the header tank.  If

overfilled, the excess coolant will be ejected when the engine is warm, and if the level is allowed to fall too low,
overheating may result.  If necessary, top up the system using an approved coolant mixture (see below) to
maintain full protection from freezing damage and corrosion.

Anti-Freeze/Corrosion Inhibitor

It is necessary that the coolant contains an anti-freeze with corrosion inhibitor to protect the engine and

heat exchangers from both frost damage, and corrosion of the metallic elements.  In order to protect against
these dangers as well as raising the boiling point of the coolant, the Elise is factory filled with a 50% concentra-
tion of Havoline XLC, which is a mono-ethylene glycol coolant using organic acid technology (OAT) to provide
increased corrosion protection compared with conventional coolant additives.  A yellow label around the header
tank neck identifies the coolant type used.  The corrosion inhibiting carboxylic acids in the OAT coolant tend to
remain in solution rather than being deposited on the internal surfaces of the cooling system, thus improving
heat transfer and extending service life.  Havoline XLC is the only recommended coolant product, and at 50%
concentration provides freezing protection down to approximately - 40°C.  Even in warm climates it is recom-
mended that the concentration is not allowed to fall below 25%, in order to maintain full corrosion protection.

The simplest means of checking the antifreeze concentration is to measure the specific gravity (density)

of the coolant at a known temperature, using a hydrometer.  The following table provides a general guide:

    Density @

Concentration

20°C

60°C

25%

1.039

1.020

33%

1.057

1.034

50%

1.080

1.057

The coolant density reflects the effective level of mono-ethylene glycol, and not the level of corrosion

inhibitors present, whose effectiveness diminishes over a period of time.  The coolant should therefore be
renewed every 4 years to ensure optimum corrosion protection.

In areas where the tap water is extremely hard (exceeding 250 parts per million), use of this water will

lead to 'furring up' of the system over a period of time.  In such areas, distilled, de-ionised or filtered rain water
should be used.

Radiator Fin Cleaning

At service intervals, the matrix of the engine cooling radiator should be checked for clogging by insects,

leaves and other debris.  If necessary, use a water jet from both above and below to clean the fins, taking care
not to damage the fragile tubes or distort the finning.  At the same time, check the integrity of all cooling system
joints, and the condition of all flexible hoses.  In snowy conditions, ensure the radiator air exit is cleared of snow
before driving the car.

KH.3 - DRAIN/REFILL PROCEDURE

To drain the engine cooling system:

1.

Remove the undertray from beneath the nose of the car.

2.

Disconnect the radiator feed and return hoses from the front ends of the thro' chassis pipes, and collect
the draining coolant.  Remove the header tank cap to speed the operation.

3.

Open the drain tap at the right hand rear of the cylinder block.

Note that draining of the heater matrix is not easily possible with the unit 'in situ', and that if draining for

the purpose of coolant change, this volume should be disregarded.