Lotus Evora, Service Notes

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Lotus Service Notes Section JL
Under normal circumstances, the hydraulic power brake system of the vehicle operates without input from
the ABS, with brake pressures governed by the force applied to the brake pedal in conjunction with vacuum
servo assistance. The ABS microprocessor receives signals from wheel speed sensors at each of the four
wheel hubs, and interprets this data to determine if any wheel is tending to lock up. If imminent lock up is
determined, the microprocessor commands solenoid valves in an electro-hydraulic unit to reduce the pressure
in that particular brake circuit in order to restore wheel speed to that providing the maximum braking force
consistent with continued wheel rotation.
When the ABS is operating, indication to the driver is provided by a ‘pulsing’ sensation felt at the brake
pedal as fluid is pumped between the master cylinder and hydraulic control unit, and also by audible clicking of
the relays and switches. These signals indicate to the driver that maximum retardation is being approached,
and that driving style should be modified to suit the conditions. The minimum stopping distance is achieved
by applying the brakes firmly and steadily, and allowing the ABS to modulate hydraulic pressure. The driver
should not attempt to emulate this process by ‘pumping’ the brake pedal, as modulation at the pedal will treat
all four wheel brakes similarly, rather than the individual wheel control governed by the electronics.
During ABS operation, the wheels may appear to lock momentarily as the wheel speed changes rapidly,
and some tyre noise (intermittent screeching) may be heard. This noise is normal and will vary with road and
tyre conditions. However, a wheel that completely locks and stays locked for more than one or two seconds
is not normal, and indicates that the vehicle should be serviced as soon as possible. The ABS cannot operate
properly if the base brake system is faulty, and will also be affected by dragging brakes, faulty wheel bearings
or other related faults.
The ABS controller constantly monitors the anti-lock system for faults, and lights a fascia tell tale if a prob-
lem is detected. Information stored in the computer’s memory may be accessed via the Lotus TechCentre in
order to facilitate diagnosis of system faults (see later).
JL.2 - TELL TALE LAMPS
Two tell tale lamps are provided in the instrument cluster to warn of problems in the brake system.
Brakes Tell Tale
LOTUS
OFF
As a bulb check function, this tell tale will glow red for about 3 seconds after ignition switch on, and then
go out unless one of the following conditions applies:
i) The parking brake is applied.
ii) The brake fluid level in the master cylinder reservoir is low.
Under normal circumstances, the tell tale should light when the ignition is switced on, and go out when
the parking brake is released. If the lamp stays on, or comes on whilst driving, the car should be stopped
immediately, as this may be an indication of low brake fluid level caused by a hydraulic leak. A button on the
reservoir cap allows the tell tale circuit to be tested.
ABS Tell Tale
LOTUS
OFF
The ABS tell tale warns the driver of problems in the anti-lock system. The lamp should light for about
3seconds following ignition switch on, and then go out. If the lamp remains lit, or comes on whilst driving, a fault
in the ABS is indicated. The base brake system will continue to operate normally, but without ABS regulation.
The car can be driven but should be checked and repaired at the earliest opportunity.
JL.3 - BRAKE FLUID CHECK & CHANGE
Before checking the brake fluid level, ensure that the car is parked on a level surface, and open the front
body access panel. The level of fluid in the reservoir may be inspected without disturbing the filler cap, and
should be level with the top of the ‘MAX’ mark moulded on the transluscent reservoir body. The level will fall
progressively as the brake pads wear in service, and should be checked at each service interval. A sensor
incorporated into the filler cap will light a tell tale lamp in the instrument cluster if the level drops significantly.