Brake systems
Introduction to the brake system
This section contains important information on the subject of brakes and is structured as follows:
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Telligent® brake system more
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Anti-lock protection function check more
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Checking the air-brake system for leaks more
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Anti-lock braking system (ABS) more
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Brake Assist more
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Parking brake more
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Frequent-stop brake more
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Hill holder more
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Continuous brake more
Telligent® brake system
The basic version of the service brake is a pneumatically
controlled brake with an anti-lock braking system (ABS).
In addition to the basic version, the service brake is also
available as a Telligent® brake system.
The Telligent® braking
system has an electronic control for regulation and monitoring of the braking
system. This also incorporates the following systems:
The Telligent®
brake system is able to relieve the load on the wheel brakes by activating the
vehicle's continuous brake (engine brake/retarder), depending on the vehicle
load and the weather conditions.
If there
are malfunctions in the brake system, a corresponding message appears in the
display.
 | Risk of accident |
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If the display shows a display message and the status indicator lights up in red, the braking characteristics of the vehicle have changed.
The pedal travel and pedal force required to brake the vehicle or the vehicle combination may increase.
The anti-lock function may be deactivated. The vehicle can only be decelerated by normal braking.
Do not pull away or, if the vehicle is already in motion, stop as soon as possible, paying attention to road and traffic conditions.
Have the brake system checked and repaired at a qualified specialist workshop which has the necessary specialist knowledge and tools to carry out the work required.
Mercedes-Benz recommends that you use a Mercedes-Benz Service Centre for this purpose. All work relevant to safety or on safety-related systems must be carried out at a qualified specialist workshop.
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| Risk of accident |
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If the display shows a display message and the status indicator lights up in yellow, the braking characteristics of the vehicle may change.
Drive with particular care.
Have the brake system checked and repaired as soon as possible at a qualified specialist workshop which has the necessary specialist knowledge and tools to carry out the work required.
Mercedes-Benz recommends that you use a Mercedes-Benz Service Centre for this purpose. All work relevant to safety or on safety-related systems must be carried out at a qualified specialist workshop.
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Anti-lock protection function check
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Turn the vehicle key to the drive position in the ignition lock.
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The display lights up for approximately 2 seconds. At the same time, the warning buzzer sounds.
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The display then either shows the message "ABS on tractor vehicle" more or "ABS on tractor vehicle and ABS on trailer/semitrailer" more.
| Risk of accident |
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The anti-lock protection function is not guaranteed unless:
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the indicator for the Telligent® brake system appears in the display or
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the indicator goes out after 3 seconds or
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the indicator goes out when the vehicle pulls away
The vehicle cannot be steered if the wheels lock while braking. The vehicle could skid due to the wheels being locked while braking. The vehicle can only be decelerated by normal braking.
Drive with particular care.
Have the brake system checked and repaired as soon as possible at a qualified specialist workshop which has the necessary specialist knowledge and tools to carry out the work required.
Mercedes-Benz recommends that you use a Mercedes-Benz Service Centre for this purpose. All work relevant to safety or on safety-related systems must be carried out at a qualified specialist workshop.
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Checking the compressed-air brake system for leaks
| Risk of accident |
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A leaking compressed-air brake system jeopardises the operating and road safety of the vehicle. It is not possible to brake the vehicle if the reservoir pressure in the compressed-air brake system is too low. You could cause an accident, thereby endangering yourself and others.
Do not pull away until the reservoir pressures have been reached and the STOP lamp has gone out.
Do not pull away or, if the vehicle is already in motion, stop as soon as possible, paying attention to road and traffic conditions, if:
Have the brake system checked and repaired at a qualified specialist workshop which has the necessary specialist knowledge and tools to carry out the work required.
Mercedes-Benz recommends that you use a Mercedes-Benz Service Centre for this purpose. All work relevant to safety or on safety-related systems must be carried out at a qualified specialist workshop.
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 | Indicator lamp for brake circuit 1 |
 | Indicator lamp for brake circuit 2 |
 | Pressure gauge for supply pressure, brake circuit 1 or 2 |
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Vehicles with on-board computer Plus:
To check for leaks, use the Supply pressure indicator in the Monitoring info menu more.
Checking with the parking brake applied
To check the compressed-air brake system for leaks when the vehicle is stationary:
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Apply the parking brake.
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In order to make sure that there are no leaks in the compressed-air system of the trailer/semitrailer, disconnect the compressed-air lines from the trailer/semitrailer more.
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Turn the vehicle key to the drive position in the ignition lock.
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Run the engine until the display shows a supply pressure of 10 bar.
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The brake circuit with the lower supply pressure is automatically displayed.
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Turn the vehicle key back fully in the ignition lock.
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The engine is switched off.
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Wait about five seconds and then turn the key to the drive position in the ignition lock.
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The compressed-air system can be regarded as being free from leaks if there is no visible drop in reservoir pressure in the brake circuits after 3 minutes.
Checking with the parking brake released or partially applied
Check the reservoirs, valves and brake cylinders on the tractor vehicle for leaks with the vehicle stationary and the parking brake released.
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Use chocks to safeguard the vehicle against rolling away more.
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At the same time, in order to make sure that there are no leaks in the compressed-air system of the trailer/semitrailer: disconnect the compressed-air lines from the trailer/semitrailer more.
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Release the parking brake.
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Run the engine until the display shows a supply pressure of 10 bar.
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Turn the vehicle key back as far as possible.
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The engine is switched off.
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Wait about five seconds and then turn the key to the drive position in the ignition.
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Depress the brake pedal enough for a partial brake application (half pedal travel). Keep the pedal position unchanged.
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The compressed-air system can be regarded as being free from leaks if there is no visible drop in reservoir pressure in the brake circuits after 3 minutes.
Anti-lock braking system (ABS)
ABS controls the
brake pressure so that the wheels will not lock when braking. This means that
the vehicle can still be steered while braking.
ABS is operational
from walking pace, regardless of road surface conditions. If the road is
slippery, ABS is active even when you only brake gently.
Braking with
anti-lock protection
You will feel the
brake pedal pulsate if ABS intervenes during braking.
When ABS is
intervening:
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Continue to depress
the brake pedal with force until the braking situation is
over.
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During full brake
application:
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Depress the brake
pedal with full force.
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| Risk of accident |
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There is a risk of accident if a trailer/semitrailer is overbraked. The wheels on the trailer/semitrailer could lock, the vehicle could become unstable and you could lose control of the vehicle as a result.
When braking, the trailer/semitrailer could be overbraked if:
Observe the reaction of the trailer/semitrailer in the exterior mirror when applying brakes fully.
Avoid applying the brakes fully, unless it is an emergency, to prevent the wheels of the semitrailer from locking. The vehicle remains stable when the wheels on the semitrailer are not locked.
The Telligent® brake system anti-lock protection does not relieve you of the responsibility of adapting your driving style to the road and traffic conditions. Directional stability and steerability of the vehicle or tractor/trailer combination when braking is improved by the anti-lock protection. The anti-lock protection is however not capable of protecting against the consequences of not maintaining a safe distance from the vehicle in front or excessive speed when cornering, for instance.
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When ABS is
intervening, the continuous brake is automatically switched off. The
indicator lamp in
the switch does not go out.
If the tractor vehicle is driven without a trailer/semitrailer or
with a trailer/semitrailer without ABS:
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insert the
connector cable into the blank socket.
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If the tractor vehicle is driven with a trailer/semitrailer with
ABS or an electronic brake system:
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remove the connector cable from the blank socket and insert it
into the trailer's/semitrailer's connector.
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Deactivating
ABS
If ABS
is deactivated, it may be possible to achieve shorter stopping distances on
rough terrain and on unmade roads (e.g. soft or extremely uneven ground).
You can only deactivate ABS for the tractor vehicle.
| Risk of accident |
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If ABS is deactivated, the wheels may lock when braked. It is no longer possible to steer the vehicle when braking with locked wheels and the vehicle could skid.
To be able to brake as quickly as possible off-road, it must be possible to deactivate ABS. ABS must be activated at all times when driving on public roads.
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ABS
deactivation switch
Reactivating
ABS
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Press the upper section of the ABS deactivation
switch.
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When ABS is
reactivated, the message in the display
disappears.
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ABS is
automatically reactivated when you restart the engine.
Brake Assist
Brake Assist operates in emergency braking situations. If you depress the brake pedal quickly, Brake Assist automatically boosts the braking force and thus shortens the stopping distance.
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Keep the brake pedal firmly depressed until the emergency braking situation has passed.
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ABS prevents the wheels from locking when this occurs.
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The brakes will function as usual once you release the brake pedal. Brake Assist is then deactivated.
If Brake Assist is faulty, the brake system function is maintained. In emergency braking situations, however, there is no automatic additional increase in the braking force and the braking distance may be increased.
Parking brake
The parking brake is designed to prevent a parked vehicle from rolling away. It actuates the spring-loaded cylinders.
| Risk of accident |
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Make sure that the parking brake lever is engaged in the fully-applied position. The lever otherwise automatically returns to the released position. The vehicle will then not be braked and could roll away.
The braking force of the spring-loaded parking brake cylinder may not be sufficient to prevent the vehicle from rolling away on uphill or downhill gradients when laden.
In the test position, check whether the braking force of the spring-loaded parking brake cylinder is sufficient to hold the laden vehicle.
Secure the vehicle and trailer/semitrailer with chocks to prevent it from rolling away.
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The lever for the parking brake may be located on the dashboard or next to the driver's seat.
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 | Applying the parking brake |
 | Releasing the parking brake |
 | Checking the parking brake (vehicles with trailer or semitrailer coupling) |
| Released position |
| Fully applied position (lever engaged) |
| Test position |
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Apply the parking brake of the trailer/semitrailer: see the manufacturer's operating instructions.
Trailer/semitrailer with EC brake system: when the trailer/semitrailer is attached, the parking brake also acts on the service brake system of the trailer/semitrailer.
You can only release the parking brake fully if the supply pressure in both brake circuits is at least 8 bar. The STOP lamp must not be lit.
If the 
indicator lamp in the instrument cluster is still lit, then the supply pressure in the spring-loaded brake circuit is too low (below 5.5 bar). To tow the vehicle, you can also release the spring actuator on the parking brake manually more.
Frequent-stop brake
The frequent-stop brake requires less compressed air than the parking brake. If the driving situation requires you to stop frequently, use the frequent-stop brake wherever possible.
Frequent-stop brake switch
| Risk of accident |
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The parking brake must be applied after parking the vehicle. The vehicle could otherwise roll away unintentionally. Chock the vehicle wheels as an additional measure if necessary (e.g. on uphill or downhill gradients).
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Activating the frequent-stop brake
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Press the upper section of the frequent-stop brake switch.
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The  indicator lamp in the instrument cluster goes out.
The frequent-stop brake is primed but not active.
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Depress the brake pedal until the vehicle is stationary.
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The frequent-stop brake is engaged and is primed automatically on pulling away.
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If the vehicle key is turned back to the stop in the ignition lock while the service brake is released and with the frequent-stop brake engaged, the warning buzzer sounds. The indicator lamp on the instrument panel will also flash.
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Apply the parking brake.
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Releasing the frequent-stop brake
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Depress the accelerator pedal.
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When the vehicle pulls away, the frequent-stop brake is automatically released.
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Deactivating the frequent-stop brake
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Press the lower section of the frequent-stop brake switch.
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The indicator lamp in the instrument cluster goes out.
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Hill holder
The hill holder is part of the Telligent® brake system and offers assistance when pulling away. If the hill holder is activated, it remains primed in forward and reverse gear at all times, even after a brief stop or after the engine is switched off.
The hill holder aids the driver when driving on uphill or downhill gradients. The hill holder prevents the vehicle rolling and enables smoother driving.
| Risk of accident |
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Do not activate the hill holder in wintry conditions. After stopping on uphill or downhill gradients, the wheels could lock and the vehicle could slip.
The hill holder is only an aid intended to assist you while pulling away.
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Activating the hill holder
Hill holder switch
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Press the upper section of hill holder switch.
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The hill holder is primed but not active.
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Depress the brake pedal until the vehicle is stationary.
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The hill holder is activated. The  indicator lamp in the instrument panel lights up.
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The hill holder remains activated as long as you depress the brake or clutch pedal.
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Releasing the hill holder
When the vehicle pulls away, the hill holder is automatically released.
The indicator lamp in the instrument panel goes out.
| Risk of accident |
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Vehicles with Telligent® automatic gearshift:
If the brake pedal is released while the hill holder is active, a warning buzzer sounds briefly. The hill holder is released and the indicator lamp in the instrument cluster goes out. The vehicle could roll away unintentionally.
Vehicles without Telligent® automatic gearshift:
If you do not depress the accelerator, clutch or brake pedal while the vehicle is stationary and the hill holder is active, a warning buzzer sounds briefly. The hill holder is released and the indicator lamp in the instrument cluster goes out. The vehicle could roll away unintentionally.
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Deactivating the hill holder
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Press the lower section of the hill holder switch.
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The indicator lamp in the instrument panel goes out. The hill holder is deactivated.
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If you apply the parking brake, the indicator lamp in the instrument panel goes out. The hill holder function is no longer active but remains primed.
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Continuous brake
The engine brake and retarder are used as a continuous brake.
When driving on long downhill gradients, shift to a lower gear in good time or activate the continuous brake to use the braking effect of the engine.
| Risk of accident |
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Do not engage the continuous brake (engine brake/retarder) on slippery road surfaces. The wheels could lock and the vehicle might skid.
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Brake the vehicle using the continuous brake as much as possible when the vehicle is in motion.
The continuous brake can be activated using the multi-function lever.
The continuous brake is automatically activated if:
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you depress the brake pedal when the vehicle is laden. If the vehicle is unladen or only partially laden, the service brake only is actuated.
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a control action of cruise control is in progress (braking cruise control).
Activating and deactivating the continuous brake
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 | Continuous brake deactivated |
 - | Brake levels |
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Vehicles without a retarder only have two brake levels (lever positions and 
).
In lever position the braking effect is lowest, in lever position it is greatest.
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To switch on: pull the multi-function lever to set to the desired brake level.
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The indicator lamp in the instrument cluster lights up.
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To switch off: pull the multi-function lever into position .
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The indicator lamp in the instrument cluster lights up.
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If the continuous brake is activated and the  indicator lamp lights up or if the continuous brake is deactivated and the indicator lamp does not go out:
have the continuous brake checked and repaired as soon as possible at a qualified specialist workshop which has the necessary specialist knowledge and tools to carry out the work required.
Mercedes-Benz recommends that you use a Mercedes-Benz Service Centre for this purpose. All work relevant to safety or on safety-related systems must be carried out at a qualified specialist workshop.
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When ABS is intervening, the continuous brake is automatically switched off. The indicator lamp in the switch does not go out.
Vehicles with Telligent® automatic gearshift
The electronic management system does not shift down if the vehicle speed is too high to shift down with the continuous brake engaged. The 
indicator lamp in the instrument panel lights up in this case.
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Decelerate using the service brake.
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The indicator lamp in the instrument cluster goes out.
If the service brake is applied when the continuous brake is active, the electronics shift down in accordance with the driving situation.
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Engine brake
The engine braking effect is dependent on the engine speed. A high engine speed means a high engine braking effect.
Note the effective engine braking range (yellow section) marked on the rev counter.
Retarder
| Risk of accident |
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If  appears in the display with a red status indicator, the retarder cannot be switched off during ABS braking regulation or by depressing the accelerator pedal.
Drive with particular care. The vehicle could brake uncontrollably. The wheels could lock, especially when driving on a slippery road surface, and the vehicle could skid.
Have the retarder checked and repaired as soon as possible at a qualified specialist workshop which has the necessary specialist knowledge and tools to carry out the work required.
Mercedes-Benz recommends that you use a Mercedes-Benz Service Centre for this purpose. All work relevant to safety or on safety-related systems must be carried out at a qualified specialist workshop.
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The retarder’s braking effect is reduced automatically, depending on the coolant temperature. If this occurs, the display shows the 
symbol.
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On long downhill gradients in particular, change down in good time to make use of the engine braking effect.
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Do not activate the retarder if the warning lamp in the instrument panel is lit with the lever in position .
Have the retarder checked and repaired as soon as possible at a qualified specialist workshop which has the necessary specialist knowledge and tools to carry out the work required.
Mercedes-Benz recommends that you use a Mercedes-Benz Service Centre for this purpose. All work relevant to safety or on safety-related systems must be carried out at a qualified specialist workshop.
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Notes on cleaning and taking care of the retarder more.
(brake system reservoir pressure) appears with the red status indicator
or 
or
indicator lamp in
the instrument cluster also lights
up.
