This article will answer the following questions: How to open a Mercedes Benz engine hood? What to do when the engine hood does not open? Why does the vehicle show the engine hood is open in the instrument cluster even when it’s closed?
How to open the engine hood in Mercedes Benz cars?
To open the Mercedes Benz engine hood, a release lever is located underneath the dashboard on the driver’s side. The lever must be pulled until the engine hood pops open and then it can be lifted in the open position.
The engine hood can stay open in the following two positions:
- Partially open
- Fully open
This position is mostly used by the customers and the hood can be kept open for a shorter duration of time. This position is suitable to check the engine oil and the coolant level and fill liquid into the windshield washer tank.
In this position is also easier to close the hood as the angle of inclination is less than 90 degrees, even customers with smaller heights can easily close the engine hood from this position.
The left side engine hood support strut has a red switch, simultaneously pressing the switch and lifting the engine hood from the partial position releases the default stop position in the support strut and the engine hood can be opened at a 90-degree angle.
This position is usually used by the technicians as it allows more space to work on the engines. More space is also needed to mount specially designed engine racks that can keep the engine suspended and allow work underneath the engine without separating the engine from the chassis.
What are the safety features of the Mercedes Benz engine hood?
A secondary engine hood release mechanism is designed in all Mercedes Benz cars for safety. The secondary release mechanism is fully mechanical and it is designed to keep the engine hood locked if it is accidentally opened while driving.
To release the secondary locking mechanism and open the engine hood completely, locate the protruded lever under the hood and move it sideways to release the lock. The lever must be kept on the side while lifting the hood otherwise it will get caught and the hood cannot be lifted completely.
On the latest models like Mercedes Benz S class W223 onwards, the engine hood release mechanism is completely electronically actuated. The releasing hand is still present however, there is no mechanical secondary release. The releasing hand itself must be pulled two times to fully release the engine hood and lift it open.
Few old models like G Wagen and the V Class have bonnet release handles near the A-pillar on the front passenger side. This is common on right-hand side steering wheel cars as only the steering position is changed in the production keeping the engine hood release switch on the front passenger side.
What to do when the Mercedes Benz engine hood does not open?
The Mercedes Benz passenger car models use a mechanical mechanism to lock the engine hood. It consists of the following components.
- Engine hood locks
The engine hood locks are mechanical latching locks that grab the brackets on the engine hood and keep the engine hood locked. The latches are attached to the mechanical cable which is connected to the release lever. Pulling on the cable brings the latches to the initial position and locks the springs connected to them, springs hold the latches in the open position. All the new generation cars like the A, B, CLA, GLA etc have only one engine hood lock as the hood is shorter and weighs less compared to the engine hood on a C or E Class.
When the engine hood does not open after pulling the release lever follow the following steps:
- Pull the release lever only once without using excessive force and try to lift the engine hood until the secondary release is accessible. Most of the time the support struts and springs get weaker and even after pulling the release lever, the hood does not pop out.
- Ask a helper to press down on the engine hood and then when it is pressed down, pull the release lever, this will help to unlatch the brackets and the engine hood can then be lifted to the open position.
- If the engine hood is still closed after following the first two steps then pull the release lever out of the dashboard panel and remove the cable fixed into the lever. Use a grip plier and pull the cable until you hear a pop sound.
The engine hood locks are subjected to external elements like water, dirt and dust. Therefore they can get stuck and not open completely. Use a lubricating spray on the engine hood locks after opening the hood. The brackets on the engine hood can also be adjusted if the force on the release lever is too strong.
Why do the Mercedes Benz cars show an engine hood open warning in the instrument cluster even when it’s closed?
All the Mercedes Benz cars have electronic engine hood switches located on the engine hood locks.
This electrical switch on the mechanical lock sends the open or close status to the front signal actuation and acquisition module. If the bonnet is not fully locked the latch only partially closes the switch and the driver gets an engine hood open message shown in the instrument cluster.
Similarly, if there is too much dirt and dust in the engine hood latch, it can get stuck halfway and not fully depress the electrical switch which can lead to an engine hood warning while driving.
Mercedes Benz uses a plausibility check on the engine hood signal. This is achieved by using two electrical switches installed on both the engine hood latches. In a closed position, one switch becomes closed while the other becomes open and the front signal actuation and acquisition control unit recognises that the engine hood is in the closed position.
There can also be an open circuit in the electrical line between the front SAM (signal actuation and acquisition module) and the electrical switches which can cause an engine hood message in the instrument cluster.
Therefore, before replacing any switch, it is important to check the electrical lines and the actual value in the front SAM control unit. If there is a malfunction of the engine hood switch, the windshield wiper also deactivates. This is done as a safeguard, if the engine hood opens and wipers are operated it can cause damage to the person working on the car.
Few latest models do not even allow the gear to go into D and show a continuous warning in the instrument cluster followed by a warning tone.
Other articles about Mercedes Benz you may be interested in
Opening and closing the Mercedes Benz engine hood is effortless and due to the electrical switches, drivers are reminded if the hood is not locked completely. The engine hood of the Mercedes Benz car is also specially designed to absorb the impact of a frontal collision and the engine hood lifters are present in the vehicle with a pedestrian protection option. The engine hood is also heavier compared to other passenger cars and makes a reassuring thump noise to indicate it is completely locked.