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How to Change Spark Plugs in a Mercedes Benz

Post Date: 11th May 2018


When you start having trouble with the daily running of your Mercedes Benz, it’s worth taking action as soon as you can. Depending on the symptoms you are experiencing, the issue can range from something very simple that you can complete yourself at home as part of regular maintenance, all the way up to a complex problem that can only be fixed by a qualified mechanic.

If the issue seems to be the former, it will fall under a simple maintenance task that can be completed at home, even if your experience of maintaining your vehicle is only limited. Changing the spark plugs is relatively simple, but if you have never done it before, it’s worth getting a bit of advice.

Have a read of our guide below that outlines how to change your spark plugs safely at home.

Tools you will need:

– Spark Plug Wrench set:

– Standard 3/”8 spark plug sockets of varying sizes

– Socket wrench or T-handle

– Spark Plug Wire Remover (17mm)

– Torque Wrench

– Replacement Spark Plugs

– Old rags for wiping hands

– Torch or lamp to illuminate the area

Step 1: – Park your vehicle on a flat surface and open the bonnet

Make sure your Mercedes Benz is parked on a flat surface with enough space for you to move round the car. Ensure the handbrake is on and the engine has been off for a few hours so it has had time to cool down.

Step 2: – Disconnect Battery

Ensuring the engine has sufficiently cooled, locate the battery in the vehicle and disconnect the negative battery cable. If you are unsure where the battery is located, it could be in the engine bay, under the rear seat or in the boot, depending on the class of vehicle you own.

Step 3: – Remove Engine Cover

Most modern Mercedes cars will have engine covers, so you will need to remove it before starting work on removing the spark plugs. Check the user manual, but most engine covers are simply held on with clips so you can pull it off with a bit of force.

Step 4: – Locate spark plugs and coils

Find the spark plugs on your Mercedes engine. The user manual may indicate this or you will be able to get advice from a mechanic if you are unsure. The thing to remember is that the amount of spark plugs you will have depends on how many cylinders the engine has:

– 6 cylinders – 12 plugs

– 8 cylinders – 16 plugs

– 12 cylinders – 24 plugs

Step 5: – Unplug ignition coil packs

Unplug the electrical connectors by gently pressing on the marked plastic tab and pulling upwards away from the ignition coil.

Step 6: – Remove ignition coil

The ignition coil pack can also be removed to make it easier for you to change the spark plug. Loosen the bolt in the middle of the pack and put aside. The ignition coil pack will now be able to be moved out of the way.

Step 7: – Remove ignition wire

Use the spark plug wire remover to remove the ignition wire – the wire should be marked with the top of the wire connected to where it has an A and the bottom of the wire connected to where it has a B.

Step 8: – Replace old spark plugs and tighten

Use the correct spark plug socket to remove the old spark plug and put aside. Replace with new spark plug and tighten accordingly. A torque wrench should allow you to correctly tighten to the required tightness, though you should also check your user manual to see how tight new spark plugs should be. Too loose and the spark plug could fall out, but if it is too tight it can lead to damaged plug threads or a cracked engine casing.

If in doubt, check with a qualified mechanic for the exact tightness before using the vehicle again.

If you need any information on replacement Mercedes parts, or are thinking of scrapping your car, get in touch with Dronsfields today for more information.

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