Mercedes A-Class Clutch Replacement Guide

Mastering the Mercedes A-Class Clutch: A Comprehensive Repair Manual

The Mercedes A-Class, a popular choice since its introduction in 1997, boasts a significant presence on UK roads, with nearly 50,000 units registered. While a beloved vehicle, its clutch replacement process is known for its complexity and time-consuming nature, often requiring over seven hours. This detailed guide is designed to equip UK aftermarket garages and discerning DIY mechanics with the knowledge to streamline this procedure, aiming to reduce the removal and installation time to under four hours. We'll delve into every crucial step, ensuring a successful and efficient clutch replacement.

Essential Preparations and Tools

Before embarking on this task, it's important to note that while no highly specialised tools are strictly required, a methodical approach and proper support systems are paramount. You will need to ensure the engine, gearbox, and subframe are adequately supported throughout the process. In our example, we utilised four transmission jacks for optimal support. Alternatively, a combination of two jacks and sturdy rope can be employed to secure the subframe. A two-post ramp is also highly recommended for safe and convenient access. Additionally, if your Mercedes A-Class is fitted with alloy wheels, be aware that they may have anti-theft locking nuts. It is imperative to locate and have the corresponding key readily available before commencing any work.

Initial Disconnections and Access

Begin by opening the bonnet. For safety, and to prevent any accidental power surges, disconnect both battery terminals. To facilitate easier access to the components beneath, it is advisable to remove the washer bottle. Next, carefully undo the steering column assembly. Proceed to unlink the gear selector cables from the gear mechanism. Once disconnected, remove them entirely from their securing bracket and stow them safely to one side, ensuring they are out of the way (refer to Figure 1 for visual guidance).

Following this, disconnect the reverse light switch. You will also need to remove the earth connection from the gearbox mount. Proper identification and removal of these connections are crucial before proceeding further (as illustrated in Figure 2).

Raising the Vehicle and Subframe Procedures

With the initial disconnections made, it's time to raise the vehicle. To avoid unnecessary work and potential complications, you can support the radiator and fan assembly to the car's body using cable ties. This allows you to bypass draining the coolant. Remove both front wheels to gain access to the subframe and associated components. Raise the vehicle to its full working height on the ramp. Now, drain the gearbox oil into a suitable container. Subsequently, remove the subframe protection covers from both the left and right-hand sides of the vehicle (as shown in Figure 3).

The next step involves loosening the ball joints on both sides of the suspension. Following this, remove both brackets that secure the anti-roll bar in place (refer to Figure 4). It is also necessary to remove the bracket that attaches the exhaust system to the gearbox (Figure 5).

Next, focus on removing the left and right-hand side brackets that connect the front bumper to the subframe. Pay close attention to the right-hand bracket, as it typically houses the ambient temperature sensor. Ensure this sensor is carefully disconnected and safely stowed away to prevent damage (Figure 6).

Supporting and Detaching the Subframe

With the surrounding components loosened, it's critical to properly support the engine, gearbox, and subframe. Utilise four axle stands for this purpose. Begin by removing the fixing bolts that attach the subframe to the vehicle's chassis. Concurrently, remove the gearbox mounting nut and the two engine mounting nuts from the brackets affixed to the subframe (Figure 7).

At the rear of the subframe, you will find two additional brackets that connect to the underside of the vehicle's body. These also need to be removed on both sides. Proceed to remove the central through bolt, the engine rear mount, and the gearbox rear mount. Locate and remove the six subframe bolts that secure it to the body. Finally, remove the left and right-side steering rack to subframe brackets.

To detach the steering pump from the subframe, loosen the hexagonal bolt; the pump should then slide up from its bracket. On the left-hand side, undo the wheel arch liner flap (Figure 8) to expose two further bolts and the A/C pipe bracket. Remove these components.

Safely stow the power steering pipes. Carefully detach the steering rack from the subframe. Using the two axle stands (or the rope system), carefully lower the front of the subframe. Ensure the steering rack and pump are securely supported during this manoeuvre.

Gearbox Removal and Clutch Inspection

Once the subframe is safely removed and stored away from the work area, you can proceed with the gearbox removal. Before disconnecting the gearbox, it is essential to disconnect the hydraulic pipes for the Concentric Slave Cylinder (CSC). Blank these pipes and stow them away securely. Remove the gearbox mount bracket. Next, remove the bolts that secure the driveshafts to the gearbox and then carefully remove the driveshafts themselves. You will then need to remove the starter motor bolts, noting that these are typically Torx bolts, and stow the starter motor to one side. The gearbox is secured by nine bell housing bolts. Carefully lower the gearbox and move it away from the work area.

With the gearbox removed, you should now have sufficient clearance to access and remove the clutch assembly. Once the clutch is out, it is crucial to inspect the flywheel for any signs of heat stress or excessive wear. Clean the splines on the first motion shaft and remove any accumulated debris from within the bell housing.

New Clutch Installation and Refitting

For the installation of the new clutch, apply a small amount of high-melting point grease to the first motion shaft splines. It is important to use a grease that is not copper-based. This lubrication will ensure the new driven plate slides freely back and forth along the shaft. This also helps to spread the grease evenly and confirms that you have the correct clutch kit. Wipe away any excess grease from both the shaft and the hub of the driven plate. Using a universal alignment tool, and ensuring the driven plate is correctly oriented (check for markings indicating the correct side), bolt the new clutch to the flywheel evenly and in a sequential tightening pattern.

Before refitting the gearbox, check that any dowels that locate the gearbox to the engine have not become dislodged or damaged. Replace any that show signs of wear or damage. Carefully reinstall the gearbox, ensuring that all securing bolts are tightened correctly. Refit all the necessary mountings before removing the supporting transmission jacks. The refitting of all other components is essentially the reverse of the removal process. Do not forget to refill the gearbox with the correct grade and quantity of oil as specified by the manufacturer.

Troubleshooting and Frequently Asked Questions

Q1: What are the common signs of a failing clutch?
A1: Common indicators include a slipping clutch (engine revs increase but vehicle speed does not), difficulty changing gears, a stiff or spongy clutch pedal, and unusual noises when the clutch is engaged or disengaged.

Q2: Can I replace the clutch myself?
A2: While it is possible for a skilled DIY mechanic with the right tools and knowledge, it is a complex and physically demanding job. If you are not confident in your mechanical abilities, it is highly recommended to seek professional assistance from a qualified garage.

Q3: How long does a clutch typically last?
A3: The lifespan of a clutch can vary significantly depending on driving style and conditions. However, a clutch can typically last between 50,000 and 100,000 miles.

Q4: Do I need to replace the flywheel when replacing the clutch?
A4: It is not always necessary to replace the flywheel, but it is essential to inspect it for wear, heat spots, or damage. If the flywheel is damaged or significantly worn, it should be replaced or skimmed by a professional to ensure proper clutch operation and longevity.

Q5: What is a Concentric Slave Cylinder (CSC), and why is it important?
A5: The CSC is an integrated hydraulic clutch release system. It's crucial to replace or inspect the CSC when replacing the clutch, as a failure in the CSC can lead to clutch operation issues and potentially damage the new clutch components.

Important Considerations for a Successful Repair

• Torque Specifications: Always adhere to the manufacturer's specified torque settings for all bolts and nuts.
• Component Quality: Use high-quality replacement clutch parts to ensure longevity and optimal performance.
• Cleanliness: Maintain a clean work environment throughout the process, especially when handling clutch components.
• Safety First: Always prioritise safety by ensuring the vehicle is securely supported and the battery is disconnected.

By following this comprehensive guide, you can significantly reduce the time and effort involved in a Mercedes A-Class clutch replacement, ensuring a professional and successful outcome for your vehicle.

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