engine overheat MERCEDES-BENZ B-CLASS HATCHBACK 2014 User Guide

Problem
Possible causes/consequences and
M
MSolutions ?
The red coolant warn-
ing lamp comes on
while the engine is run-
ning.
The coolant level is too low.
If the coolant level is correct, the airflow to the engine radiator may
be blocked or the electric engine radiator fan may be malfunc-
tioning.
The coolant is too hot and the engine is no longer being cooled
sufficiently.
X Observe the additional display messages in the multifunction
display.
X Stop the vehicle immediately, paying attention to road and traf-
fic conditions, and switch off the engine.
X Secure the vehicle against rolling away (Y page 181).
X Leave the vehicle and keep a safe distance from the vehicle until
the engine has cooled down.
X Check the coolant level and top up the coolant, observing the
warning notes (Y page 322).
X If you have to top up the coolant frequently, have the engine
cooling system checked.
X Make sure that the air supply to the engine radiator is not
blocked, e.g. by frozen slush.
X Do not start the engine again until the coolant temperature is
below 120 †. The engine may otherwise be damaged.
X Drive to the nearest qualified specialist workshop.
X Avoid putting the engine under heavy load as you do so, e.g.
driving in mountainous terrain and stop-start traffic. ?
The red coolant warn-
ing lamp comes on
while the engine is run-
ning. A warning tone
also sounds.
The coolant temperature has exceeded 120 †. The airflow to the
engine radiator may be blocked or the coolant level may be too
low.
G WARNING
The engine is not being cooled sufficiently and may be damaged.
Never drive with an overheated engine. Driving when your engine is overheated can cause some fluids which may have leaked into
the engine compartment to catch fire.
In addition, steam from an overheated engine can cause serious
burns, which can occur just by opening the bonnet.
There is a risk of injury.
X Observe the additional display messages in the multifunction
display.
X Stop the vehicle immediately, paying attention to road and traf-
fic conditions, and switch off the engine.
X Secure the vehicle against rolling away (Y page 181).294
Warning and indicator lamps in the instrument clusterOn-board computer and displays

Useful information
i This Owner's Manual describes all mod-
els, series and optional equipment for your
vehicle that were available at the time of
going to press. National variations are pos- sible. Note that your vehicle may not be
equipped with all of the functions descri-
bed. This is also the case for systems and
functions relevant to safety.
i Read the information on qualified special-
ist workshops: (Y page 24). Engine compartment
Bonnet
Important safety notes G
WARNING
An unlocked bonnet may open up when the
vehicle is in motion and block your view. There is a risk of an accident.
Never unlock the bonnet when driving. Before
every trip, ensure that the bonnet is locked. G
WARNING
When being opened and closed, the bonnet
may suddenly fall into the closed position.
There is a risk of injury to persons in the range of movement of the bonnet.
Open and close the bonnet only when nobody
is in the range of movement. G
WARNING
If you open the bonnet while the engine is
overheating or while there is a fire in the
engine compartment, you could come into
contact with hot gases or other leaking ser-
vice products. There is a danger of injury.
Allow an overheating engine to cool down
before opening the bonnet. If there is a fire in the engine compartment, leave the bonnet
closed and notify the fire brigade. G
WARNING
There are moving components in the engine
compartment. Certain components may con-
tinue to move or suddenly move again even
after the ignition has been switched off, e.g.
the radiator fan. There is a risk of injury.
If you have to carry out work in the engine
compartment:
R switch off the ignition
R never touch the dangerous areas surround-
ing moving components, e.g. the rotation
area of the fan
R remove jewellery and watches
R keep items of clothing and hair, for exam-
ple, away from moving parts. G
WARNING
The ignition system and the fuel injection sys- tem operate with a high voltage. If you touch
the live components, you could receive an
electric shock. There is a danger of injury.
Never touch components of the ignition sys-
tem or the fuel injection system when the
ignition is switched on.
Opens the bonnet G
WARNING
Certain components in the engine compart-
ment could be very hot, e.g. the engine, the
radiator and parts of the exhaust system.
There is a risk of injury when accessing the
engine compartment.
As far as possible, allow the engine to cool
down and only touch the components descri- bed in the following. G
WARNING
When the bonnet is open, and the windscreen wipers are set in motion, you can be injured by
the wiper linkage. There is a risk of injury.
Always switch off the windscreen wipers and
the ignition before opening the bonnet. 318
Engine compartmentMaintenance and care

used. The low-temperature properties of
engine oils can be significantly impaired dur-
ing operation due to, for example, ageing or
soot and fuel accretion. It is therefore
strongly recommended to observe regular oil changes using an approved engine oil with the
appropriate SAE classification. Brake fluid
G
WARNING
The brake fluid continuously absorbs mois-
ture from the air. This results in the boiling
point of the brake fluid lowering. If the boiling
point of the brake fluid is too low, vapour
pockets may form when the brakes are sub-
jected to a heavy load. This would impair brak- ing efficiency. There is a risk of an accident.
Have the brake fluid renewed at the prescri-
bed intervals.
When handling brake fluid, observe the
important safety notes on service products
(Y page 386).
The brake fluid change intervals can be found in the Service Booklet.
Only use brake fluid approved by Mercedes-
Benz according to MB Approval 331.0.
Information about approved brake fluid can
be obtained at any qualified specialist work-
shop or on the Internet at
http://bevo.mercedes-benz.co m.
i Have the brake fluid regularly replaced at
a qualified specialist workshop and the
replacement confirmed in the Service
Booklet. Coolant
Important safety notes G
WARNING
If antifreeze comes into contact with hot com- ponents in the engine compartment, it may
ignite. There is a risk of fire and injury. Let the engine cool down before you top up
the antifreeze. Make sure that antifreeze is
not spilled next to the filler neck. Thoroughly
clean the antifreeze from components before starting the engine.
! Only add coolant that has been premixed
with the desired antifreeze protection. You
could otherwise damage the engine.
Further information on coolants can be
found in the Mercedes-Benz Specifications for Service Products, MB Specifications for
Service Products 310.1, e.g. on the Inter-
net at http://bevo.mercedes-benz.com.
Or contact a qualified specialist workshop.
! Always use a suitable coolant mixture,
even in countries where high temperatures prevail.
Otherwise, the engine cooling system is not
sufficiently protected from corrosion and
overheating.
i Have the coolant regularly replaced at a
qualified specialist workshop and the
replacement confirmed in the Service
Booklet.
Comply with the important safety precautions for service products when handling coolant
(Y page 386).
The coolant is a mixture of water and anti-
freeze/corrosion inhibitor. It is responsible
for the following:
R anti-corrosion protection
R antifreeze protection
R raising the boiling point
If antifreeze/corrosion inhibitor is present in
the correct concentration, the boiling point of
the coolant during operation will be approx-
imately 130 †. 392
Service products and capacitiesTechnical data