Common symptoms of a bad timing chain tensioner include:
What you will need
- Park the vehicle on level ground and set the parking brakes.
- Allow the engine to cool down.
- Pull the hood release under the dashboard and open the hood.
- Disconnect the battery negative terminal. The battery will be in the trunk, under the passenger seat, or the engine bay. Depending on the model.
- Create a simple drawing of the route of the serpentine belt.
- Use a 27mm socket and ratchet to turn the crankshaft clockwise. Set the crankshaft at forty degrees. Turn crankshaft clockwise only. Crankshaft degrees are stamped on the inner side of the crankshaft pulley.
- Use a 17mm socket and ratchet to loosen the serpentine belt tensioner.
- Remove the serpentine belt.
- Use the E12 socket to remove the four bolts that secure the alternator.
- Remove the ground, positive and main connector from the alternator.
- Move the alternator out of the way. You can lower the alternator. It should give you enough room to access the timing chain tensioner. If you prefer remove the alternator from the engine bay.
- Place an oil pan directly below the chain tensioner for catching the oil.
- Remove the timing chain tensioner using a 19mm socket.
- Install the new timing chain tensioner. Using a torque wrench, torque the tensioner bolt to specs. Typically 80 Nm. Verify by calling your Mercedes-Benz dealer.
- Reconnect alternator wires. Reinstall alternator bolts.
- Remove the rubber cap (behind the last ignition coil, driver side) at the back of the engine and insert a T60 wrench.
- Extend the timing chain tensioner by turning the crankshaft counterclockwise while holding the wrench. This will open the timing chain tensioner. When the timing chain is installed, it is in a closed position. You must carry this step so that the timing tensioner releases.
- Reinstall the serpentine belt.
- Do not start the engine yet. Double-check the installation by turning the crankshaft in a full 360 turn using a 27 mm wrench at the crankshaft bolt. Do not start the engine, if you are not able to rotate the crankshaft by hand.
- Reconnect the battery.
Frequently Asked Question
How do you know your timing chain tensioner is bad?
- One of the common symptoms of timing chain tensioner problems is a tapping noise when you start the engine in the morning which goes away after a while.
Can you drive a Mercedes-Benz with a bad timing chain tensioner?
- It is not recommended to drive with a bad timing chain tensioner. If the tensioner or timing chain fails, it can cause catastrophic engine failure.
Mercedes-Benz vehicles are equipped with M272 and M273 engines.