Replacing Spark Plugs on Mercedes Benz W123 - iFixit Repair Guide

What you need

Step 1 Spark plugs

Replacing Spark Plugs on Mercedes Benz W123, Spark plugs: step 1, image 1 of 2

Replacing Spark Plugs on Mercedes Benz W123, Spark plugs: step 1, image 2 of 2

First, you must buy spark plugs that correspond to the engine or their equivalent. Consult the owner's manual.
To begin, disconnect the cables of each spark plug. Grip them by the base and pull them out firmly.

Step 2

Replacing Spark Plugs on Mercedes Benz W123: step 2, image 1 of 2

Replacing Spark Plugs on Mercedes Benz W123: step 2, image 2 of 2

Next, you must use a spark plug wrench. Apply force while twisting counterclockwise, until you remove the spark plug.

Step 3

Replacing Spark Plugs on Mercedes Benz W123: step 3, image 1 of 2

Replacing Spark Plugs on Mercedes Benz W123: step 3, image 2 of 2

Insert the new spark plug. Be careful to not let the new spark plug fall because it can alter the opening of the electrode. It is recommended to use a piece of hose or a wrench to insert it carefully, turning it in a clockwise direction BY HAND to avoid damaging the threads if inserted wrong.
Then tighten with the wrench until snug, without over tightening, which can cause the threads or the spark plug itself to be damaged. Remember, also, that the sparks may need to removed in the future.
Once all the spark plugs are adjusted, reconnect the spark plug wires and enjoy.

Conclusion

To reassemble, follow these instructions in reverse.

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