Lotus Elise Service Notes page 339

D Lotus Service Notes Section JH
WARNING: Do NOT remove the cap 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. A good quality mono-ethylene
glycol anti-freeze, provides protection against these dangers as well as raising the boiling point of the coolant.
The car is factory filled, for all markets, with a 50% concentration of anti-freeze which provides freezing
protection down to approximately - 35°C. In warm climates it is recommended 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 24 months 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.
KF.3 - DRAIN/REFILL PROCEDURE
To drain the engine cooling system, remove the header tank cap, and disconnect the radiator feed and
return hoses from the rear ends of the water rails running down each sill. If necessary, raise the front of the car
to aid draining. 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.
Page 339 1998 / 03