11 2FUNCTIONS OF ENGINE OIL
Engine oil has the primary functions of lu-
bricating and cooling the inside of the en-
gine,
and plays a major role in maintaining
the engine in proper working order. ENGINE OIL CONSUMPTION
It is normal that an engine should con-
sume some engine oil during normal
engine operation. The causes of oil
consumption in a normal engine are
as follows. Oil is used to lubricate pistons, piston
rings and cylinders. A thin film of oil is left on the cylinder wall when a piston
moves downwards in the cylinder.
High negative pressure generated
when the vehicle is decelerating sucks
some of this oil into the combustion
chamber. This oil as well as some part
of the oil film left on the cylinder wall is
burned by the high temperature com-
bustion gases during the combustionprocess.
Oil is also used to lubricate the stems
of the intake valves. Some of this oil is
sucked into the combustion chamber
together with the intake air and is
burned along with the fuel. High tem-perature exhaust gases also burn the
oil used to lubricate the exhaust valve stems.
The amount of engine oil consumed
depends on the viscosity of the oil, the
quality of the oil and the conditions
the vehicle is driven under. More oil is consumed by high-speed driv-
ing and frequent acceleration and decel- eration.
A new engine consumes more oil, since
its pistons, piston rings and cylinder walls
have not become conditioned.
When judging the amount of oil con-
sumption, note that the oil may be-come diluted and make it difficult to
judge the true level accurately.
As an example, if a vehicle is used for re-
peated short trips, and consumes a nor- mal amount of oil, the dipstick may not
show any drop in the oil level at all, even after 1000 km (600 miles) or more. This is because the oil is gradually becoming
diluted
with fuel or moisture, making it ap-
pear that the oil level has not changed.
The diluting ingredients evaporate out
when the vehicle is then driven at high
speeds, as on an expressway, making itappear that oil is excessively consumed
after driving as high speeds.
IMPORTANCE OF ENGINE OIL LEVEL CHECK
One of the most important points in proper vehicle maintenance is to keep the engine
oil at the optimum level so that oil function
will not be impaired. Therefore, it is essen-
tial that the oil level be checked regularly.
Toyota recommends that the oil level bechecked every time you refuel the vehicle.
Failure to check the oil level regular-
ly could lead to serious engine
trouble due to insufficient oil.
NOTICE
For detailed information on the oil level
check, see Checking the engine oil levelº
in Chapter 7-2.
Facts about engine oil consumption
11 3
TANDEM MASTER CYLINDER BRAKE SYSTEM
The tandem master cylinder brake sys-
tem is a hydraulic system with two sepa-
rate sub-systems. If either sub-system
should fa
il, the other will still work. Howev-
er, the pedal will be harder to press, and
your stopping distance will be longer.
Also, the brake system warning light may come on.
CAUTION!
Do not drive your vehicle with only a single brake system. Have your
brakes fixed immediately.
BRAKE BOOSTER
The brake booster uses engine vacuum to
power-assist the brakes. If the engine
should quit while you are driving, you can
bring the vehicle to a stop with normal
pedal pressure. There is enough reserve vacuum for one or two stopsÐbut nomore!
CAUTION!
Do not pump the brake pedal if the
engine stalls. Each push on the
pedal uses up your vacuum re- serve.
Even if the power assist is com-
pletely lost, the brakes will still
work. But you will have to push
the pedal hardÐmuch harder
than normal. And your braking
distance will be longer.
ANTI-LOCK BRAKE SYSTEM (with ABSº warning light)
The anti-lock brake system is designed to
automatically help prevent lock-up of the
wheels during sudden braking or braking on slippery road surfaces. This assists in
providing directional stability and steeringperformance of the vehicle under these circumstances.
The anti-lock brake system becomes op- erative after the vehicle has accelerated
to a speed in excess of approximately 10
km/h (6 mph). It stops operating when the
vehicle decelerates to a speed below
approximately 5 km/h (3 mph). You may hear a sound in the engine
compartment for a
few seconds when the
engine is started or just after the vehicle is started. This means that the anti-lock
brake system is in the self check mode,
and does not indicate a malfunction.
Effective way to press the ABSº brake
pedal: When the anti-lock brake system
function is in action, you may feel the brake pedal pulsating and hear a noise.
In this situation, to let the anti-lock brake
system work for you, just hold the brake
pedal down more firmly. Do not pumpthe brake. This will result in reduced
braking performance.
The brake pedal pulsation caused by the
anti-lock brake system may indicate haz- ardous road surface conditions. Althoughthe anti-lock brake system assists in pro-
viding vehicle control, it is still important to
drive with all due care, because the anti-
lock brake system cannot overcome the
laws of physics that act on your vehicle: Braking capab ility is dependent on tire
friction with the road surface.
Brake system