Mercedes-Benz Timing Chain Tensioner Replacement

Is your Mercedes-Benz engine misfiring, noisy idling, and the check engine light is on due to a faulty timing chain tensioner? Learn how to fix the problem by replacing the timing chain tensioner of your Mercedes-Benz.

This guide provides instructions on replacing the timing chain tensioner on a Mercedes-Benz E, C, S, CLS, ML, GL, and R Class from 2006 to 2012 equipped with the V6 and V8 gasoline M272 and M273 engines.

Symptoms

Common symptoms of a bad timing chain tensioner include:

• Rattling noise at startup
• Check engine light on
• Engine misfire
• Engine noise at idle

What you will need

Parts

• Mercedes-Benz Timing Chain Tensioner

Tools

• Torque Wrench
• Ratchet Wrench
• 27 MM Socket
• 19 MM Socket
• E12 Socket
• T60 Wrench

Procedure

1. Park the vehicle on level ground and set the parking brakes.
2. Allow the engine to cool down.
3. Pull the hood release under the dashboard and open the hood.
4. Disconnect the battery negative terminal. The battery will be in the trunk, passenger seat, or engine bay depending on the model.
5. Create a simple drawing of the route of the serpentine belt.
6. Use a 27mm socket and ratchet to turn the crankshaft clockwise. Set the crankshaft at forty degrees. Turn the crankshaft clockwise only.  Crankshaft degrees are stamped on the inner side of the crankshaft pulley. 
7. Use a 17mm socket and ratchet to loosen the serpentine belt tensioner.
8. Remove the serpentine belt.
9. Use the E12 socket to remove the four bolts that secure the alternator.
10. Remove the ground, positive, and main connector from the alternator.
11. 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.
12. Place an oil pan directly below the chain tensioner to catch the oil.
13. Remove the timing chain tensioner using a 19mm socket.
14. 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.
15. Reconnect alternator wires. Reinstall alternator bolts.
16. Remove the rubber cap (behind the last ignition coil, driver side) at the back of the engine and insert a T60 wrench.
17. 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.
18. Reinstall the serpentine belt.
19. Do not start the engine yet. Double-check the installation by turning the crankshaft in a complete 360 turn using a 27 mm wrench at the crankshaft bolt. Do not start the engine if you cannot rotate the crankshaft by hand.
20. Reconnect the battery.

Additional Video

Frequently Asked Question

How do you know your timing chain tensioner is terrible?

• 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.

Applications

Mercedes-Benz vehicles are equipped with M272 and M273 engines.

We hope you find the Mercedes-Benz Timing Chain Tensioner Replacement guide helpful. Check these troubleshooting and repair guides for more help on your Mercedes-Benz.