Mercedes-Benz Unimog U 20 User manual

Unimog U 20 / U 300 / U 400 / U 500
Tips on maintaining the value of your vehicle

Chassis and underbody protec-
tion ......................................................... 8
Maintaining the anti-corrosion pro-
tection .................................................... 8
Chassis ................................................... 8
Radiator .................................................. 9
Cab interior ............................................ 9
Heating/ventilation blower ................ 10
Service brake ....................................... 10
Brake unit ............................................ 11
7
Cleaning the vehicle

Chassis and underbody protection
The Unimog's chassis and underbody have
been treated with a special dual-layer protec-
tive coating.
This dual-layer protection consists of a pene-
trating wax (Carlofon 3650) and an under-
body protection wax (Carlofon 4941). The
penetrating wax improves the anti-corrosion
protection on moving parts and at gaps, joints
and overlaps. The underbody protection wax
permanently seals the chassis.
Maintaining the anti-corrosion protec-
tion
To maintain the anti-corrosion protection,
please observe the following:
RDo not clean the vehicle for the first time
until at least 4 weeks after it has been
delivered.
RWhen using a high-pressure cleaner to
clean the chassis and the underbody, the
water temperature may not exceed 40 †
and the water pressure may not exceed
30 bar. Make sure that the distance
between the vehicle and the nozzle is at
least 30 cm.
ROnly use a pH-neutral cleaner, not alkaline
or acidic products.
RDo not use any petrol-based substances,
rape seed oil, petrol, diesel or other sol-
vents. They can cause the dual-layer pro-
tection to dissolve or peel off.
RDo not use any additional anti-corrosion
agents.
RWhenever the vehicle is used in extreme
conditions, remove all traces of corrosive
substances with water afterwards.
Particularly critical locations in which these
corrosive substances accumulate are:
-on the underbody
-in the wheel arches and the steps
-on the spring assemblies
-on the drive train
-between cab and platform or mounted
equipment
-in the cab interior
RClean the Unimog at least once a week.
RThe engine compartment can be treated
using a special sealant (AP1505).
RAfter cleaning, check the chassis and
underbody protection and touch it up
where necessary.
These measures will help to prevent mechan-
ical or electrical components from malfunc-
tioning.
Chassis
The following components should be cleaned
regularly:
Rfront flap (U 300/400/500)
Rcab
Rplatform
Rcab underbody (U 20)
Rcab support frame (U 300/400/500)
Rcondenser, oil cooler (U 20)
Rwheel arches
Rvehicle underside
Cleaning equipment settings
Water temperature: max. 40 †
Water pressure: max. 30 bar
Nozzle distance: min. 30 cm
8Chassis
Cleaning the vehicle

Example: condenser, oil cooler for U 20
Example: cab support frame, U 300/400/500
Radiator
Winter road service operations
The fan sucks in snow particles, salt and dust.
This mixture accumulates in the radiators and
condenses if cleaning is neglected.
To avoid impaired cooling and engine per-
formance, all radiators must be cleaned once
a day. Impaired cooling and engine perform-
ance can result in the vehicle breaking down.
In the case of compacted dirt:
XFlush the radiator fins with lukewarm tap
water.
In the case of stubborn deposits:
XCarefully clean the radiator with a high-
pressure cleaner; see the vehicle's Operat-
ing Instructions.
! Only direct the compressed-air, steam or
water jet towards the radiator surface in a
vertical direction. Ensure that the radiator
fins are not damaged. Remove any dirt from
the radiator fins. Damaged or dirty radiator
fins can cause the engine to overheat. If
there is a loss of coolant or damage to the
cooling and heating system, have it
checked at a qualified specialist workshop.
After every extreme winter road service oper-
ation:
XCheck the radiator (visual inspection).
Summer operation
Clean the radiator every day in the case of
heavy soiling during mowing operation.
XRemove grass and plant cuttings.
XClean the radiator fins using compressed
air.
Cab interior
Cab floor
When getting in, snow, dirt and salt will inevi-
tably be carried into the cab interior. This cor-
rosive mixture accumulates in the footwell
area and promotes corrosion of the electrical
and other components in the interior.
iMercedes-Benz recommends that you
use floormats. Floormats can be removed
and cleaned if dirty or wet. This prevents
damage to the cab floor from residual
dampness.
XRegularly remove and clean the floor cov-
ers.
XClean the cab floor.
XDry off moist residue immediately.
XIn case of dry dust and salt residue: vacuum
and clean the cab interior, particularly in
the corners and pedals.
Cab interior 9
Cleaning the vehicle

Cable guides
iCorrectly seal the cable guides on the
bulkhead of the cab after changing devices.
If the cable guides have not been correctly
sealed, the cab can become damp. This can
cause corrosion to electric and other com-
ponents in the interior. Observe the infor-
mation contained in the vehicle's Operating
Instructions.
Heating/ventilation blower
U 300/400/500 only.
The blower draws in snow powder, salt and
dust which has collected in the ventilation fil-
ter housing.
For heavy-duty snow-clearing operations,
clean the ventilation filter housing weekly to
avoid malfunctions in the ventilation and
heating systems:
XOpen the front flap; see the vehicle's Oper-
ating Instructions.
XPull housing lid : from the side retention
clips and remove it in an upwards direction.
XRemove fresh air/air recirculation flap =
together with connecting rod ;.
XRemove the retaining grille together with
the ventilation filter mat by handles ?.
XClean the ventilation filter housing.
XInstall the retaining grille together with the
ventilation filter mat.
XInstall fresh air/air recirculation flap =
together with connecting rod ;.
XInstall housing cover :.
XClose the front flap; see the vehicle's Oper-
ating Instructions.
Service brake
Clean the service brakes after winter to avoid
incurring damage.
XRaise the vehicle, secure it using jack
stands and remove the wheels; see the
vehicle Operating Instructions.
Example: disc brake
10 Service brake
Cleaning the vehicle

XObserve the notes on care (Y page 14).
XThoroughly clean the hub-drive housings,
contact surfaces between the wheel rims
and wheel hub :, brake discs ; and cal-
lipers =.
XFit the wheels and lower the vehicle; see
the vehicle Operating Instructions.
XCarefully test the brakes.
Brake unit
U 300 only.
Check the brake unit monthly for dust and
moisture build-up.
Corrosive mixtures which have accumulated
attack valves and compressed-air lines if they
are not properly cleaned.
XRemove the cover of brake unit :.
XVacuum dust and salt deposits, especially
from corners and valves.
XClean brake unit : thoroughly with water
and then let it dry.
XReplace the cover of brake unit :.
Brake unit 11
Cleaning the vehicle

12

Notes on care ...................................... 14
Compressed-air dryer ......................... 14
Gearshift linkage on the transmis-
sion ....................................................... 14
Steering spindle .................................. 14
ALB controller ...................................... 15
Cab tilt lock ......................................... 15
Tipper cylinder .................................... 15
Electrical contacts .............................. 16
Battery isolator switch ....................... 16
Batteries .............................................. 16
Fuses on the battery compart-
ment ..................................................... 16
Dual-layer protective coating ............. 17
Paintwork damage and corrosion
damage ................................................ 17
Engine compartment .......................... 17
Cab ....................................................... 17
Trailer tow hitch .................................. 17
13
Maintenance and care

Notes on care
After the winter season:
XRaise the vehicle, secure it using jack
stands and remove the wheels; see the
vehicle Operating Instructions.
XClean the contact surfaces between the
wheel rim and the wheel hub and lightly
coat them with penetrating wax (Carlo-
fon 3650).
XCheck the wheel rims for corrosion damage
and cracks and replace the wheel rims
where necessary.
XFit the wheels and lower the vehicle; see
the vehicle Operating Instructions.
After every off-road use:
XCheck the frame, chassis parts and cab for
damage to the paintwork and to the pro-
tective agents and have any damage recti-
fied immediately.
To remove defects or re-apply dual-layer pro-
tection, please consult a qualified specialist
workshop. It has the necessary specialist
knowledge, tools and qualifications to cor-
rectly carry out the work required on your
vehicle. Mercedes-Benz recommends that
you use a Mercedes-Benz Service Centre for
this purpose.
Compressed-air dryer
Example: drain plugs
XEvery 3 months, unscrew drain plugs : on
the compressed-air reservoirs up to 1/4
turn, until compressed air escapes.
If condensed water is emitted, the granu-
late cartridge must be renewed; see the
vehicle's Operating Instructions.
Gearshift linkage on the transmission
Example: ball sockets
XU 20: clean and grease ball sockets : on
the gearshift linkage of the working gears
and on the planetary gear set.
X U 300/400/500: clean and grease ball
sockets : on the gearshift linkage of the
working and crawler gears as well as on the
planetary gear set.
Steering spindle
High-pressure cleaning or spray water may
cause the needle bearing grease on the
centre universal joint of the steering spindle
to be washed out. This causes the steering to
be unresponsive or stick. This can be preven-
ted by protecting the needle bearing using a
protective sleeve.
14 Steering spindle
Maintenance and care

The protective sleeve is available as a Unimog
accessory.
ALB controller
Ball sockets for ALB controller, U 20
Ball sockets for ALB controller, U 300/400/500
XClean and grease ball sockets : on the
linkage of the ALB controller.
Cab tilt lock
U 20 cab tilt lock
U 300/400/500 cab tilt lock
XU 20: clean, oil and grease cab tilt lock :.
XU 300/400/500: clean and oil cab tilt
lock :.
Do not grease cab tilt lock :.
Tipper cylinder
If the quick-change platform has been
removed, make sure that the connection part
for the quick-change platform has engaged in
the spring catches. In this way, you can pre-
vent corrosion and damage to the tipping cyl-
inder.
XRetract tipping cylinder :; see the vehi-
cle's Operating Instructions.
XGrease the cylinder units of the tipping cyl-
inder with multipurpose grease.
Tipper cylinder 15
Maintenance and care

Electrical contacts
Connector pins (example)
At least once a year or after operation in ardu-
ous conditions such as fording or driving on
roads treated with wet salt:
XTurn the vehicle key fully back in the igni-
tion lock.
XSpray the electric contacts on connector
pins : with contact spray.
Battery isolator switch
Battery isolator switch in the battery compartment
(example)
gDisengaging
1Engaging
XPull out the control lever of the battery iso-
lator switch; see the vehicle's Operating
Instructions.
XLubricate the operating lever guide with
acid-proof grease.
Batteries
! Please observe the following points:
RDirty battery terminals and battery sur-
faces cause leak currents, which lead to
the batteries discharging. Always keep
the battery terminals and battery surfa-
ces clean and dry. Lightly grease the bat-
tery terminals, especially the undersides,
with acid-resistant grease.
ROnly clean batteries with the cell caps
fitted. Otherwise, dirt can enter the bat-
tery cells.
RCleaning agents containing fuel corrode
the battery housing. Only clean the bat-
tery housing with commercially available
cleaning agents.
RThe vent holes of the cell caps must be
open. Otherwise, gases cannot escape.
Clean blocked vent holes with a suitable
tool, e.g. a piece of wire. Unscrew the cell
caps first. Otherwise, there is the risk of
a short circuit.
RIf batteries that are not in use have a no-
load voltage of less than 12.4 V, they
must be recharged.
XCheck the battery fluid level; see the vehi-
cle Operating Instructions.
XDisconnect the batteries; see the vehicle
Operating Instructions.
XClean battery terminals and grease lightly
using acid-proof grease.
XThoroughly clean the battery compartment
with water and allow it to dry.
XReconnect the batteries; see the vehicle
Operating Instructions.
Fuses on the battery compartment
U 300/400/500 only.
16 Fuses on the battery compartment
Maintenance and care

:Telligent® automatic gearshift (Automa-
ticShift®) fuse
;Fuse for equipment power socket
=Fuse for intake air pre-heating
XInterrupt the power supply using the bat-
tery isolator switch; see the vehicle's Oper-
ating Instructions.
XRemove the battery cover; see the vehicle's
Operating Instructions.
XSpray the connections in the battery com-
partment with contact spray and lubricate
them with acid-proof grease.
XReplace the battery cover; see the vehicle's
Operating Instructions.
XRestore the power supply using the battery
isolator switch; see the vehicle's Operating
Instructions.
Dual-layer protective coating
XCheck the protective agents every week.
XHave paint and corrosion damage repaired
immediately.
To remove defects or re-apply dual-layer pro-
tection, please consult a qualified specialist
workshop. It has the necessary specialist
knowledge, tools and qualifications to cor-
rectly carry out the work required on your
vehicle. Mercedes-Benz recommends that
you use a Mercedes-Benz Service Centre for
this purpose.
Paintwork damage and corrosion
damage
To repair paint and corrosion damage, please
consult a qualified specialist workshop. It has
the necessary specialist knowledge, tools
and qualifications to correctly carry out the
work required on your vehicle. Mercedes-
Benz recommends that you use a Mercedes-
Benz Service Centre for this purpose.
Engine compartment
XAfter cleaning the engine compartment:
spray the engine attachments and the
engine compartment with engine sealant.
Cab
Unimog 20:
XCheck the body cavity sealing once a year
and touch up where necessary.
Unimog 300/400/500:
XAfter cleaning the body cavities of the cab
frame, apply body cavity sealing.
XCheck the body cavity sealing once a year
and touch up where necessary.
XRenew the body cavity sealing every 3
years.
Trailer tow hitch
Trailer tow hitch 17
Maintenance and care

Always keep the coupling bolts and the tow-
ing eye bush clean and lubricated. This will
reduce wear and tear on these parts. If the
coupling mechanism is sluggish, lubricate the
coupling head above the conical lubricating
nipple :.
18 Trailer tow hitch
Maintenance and care