The following steps should always be carried out in the specified order before working in the engine compartment :

Park the vehicle on a level and stable surface.

Depress and hold the brake pedal until the engine has stopped.

Apply the handbrake firmly Braking, stopping and parking Brakes Parking .

Select the neutral position or move the selector lever to P Changing gear Changing gear Automatic gearbox see Automatic gearbox_0 Automatic gearbox see Changing gear_0 Automatic gearbox Manual gearbox see Changing gear_0 Manual gearbox .

Stop the engine and remove the key from the ignition Starting and stopping the engine Engine and ignition Ignition see Engine and ignition_6 .

Allow the engine to cool sufficiently.

Children and other people should be kept well away from the engine compartment.

Ensure that the vehicle cannot roll away unexpectedly.

WARNING
Preparing the vehicle for working in the engine compartment
Opening and closing the bonnetA/C Programmer -J127
This programmer switches the refrigerant flow direction
through the second evaporator if the temperature on the cooling
fins on the second evaporator lowers to the freezing point for
water (icing protection).
...
Wax Underbody Protection -D 316 D38 A2-
Definition:
Wax Underbody Protection -D 316 D38 A2-
Edition 04/2009
Product Description
Wax Underbody Protection -D 316 D38 A2- is an
solvent-containing anti-corrosion agent ...
General Information
A new repair concept has been developed for repairing washer
system hoses. Various individual hose connectors, adapters,
Ethylene Propylene Diene Methylene (EPDM) rubber hoses and
shrink tubing will be offered as replacement parts.
...