SL550 Spark Plug Job
 

Just posted this as a reply to the DIY thread and thought I would place it here as well; this is a DIY spark plug job with Weistec double-iridium silver-core plugs.

Tools needed are:

- 3/8" drive torque wrench
- 1/4" drive socket wrench
- E8 Torx swivel socket
- 12-point spark plug swivel socket
- various 1/4" and 3/8" extensions
- wire (shark) leader + crimps
- 7mm socket (for hose clamps)

I am not sure why anyone is using wrenches to pull the connectors; there isn't enough room for anything - I even bought a fancy set of BERU pliers from Baum tools that ended up being totally worthless; here is what you need:

https://preview.ibb.co/numW5v/IMG_0224.jpg

You take this and do a crimp loop and then a loop-to-loop connection over the connector; make sure you slide the loop UNDER the plastic tab so you don't damage the coil pack connection:

https://preview.ibb.co/fBkSCa/IMG_0201.jpg

Here's the first one removed:

https://preview.ibb.co/iZrdJF/IMG_0205.jpg

https://preview.ibb.co/fxxkyF/IMG_0204.jpg

Here is what you need for proper indexing; the correct torque per Weistec is 20 N-m which is around 14.75 ft-lbs on the standard torque wrench; torqueing to that puts the ground strap directly under the plug and faces the electrode right at the piezo injector; I taped a piece of paper with red line to the socket extensions just in case:

https://preview.ibb.co/eoZR5v/IMG_0200.jpg

Job went perfectly smooth and easy without destroying any connectors - don't waste time with stupid wrenches in such a tight space, and be sure to put dielectric grease on the ends of the connectors before re-inserting them. Also be sure to crimp a wire loop around the swivel joint of the spark plug socket because it will likely get stuck on the plug with torqueing.

Now my computer is off to Weistec for reprogramming. :naughty:

Nice job and write up.
Very few folks have the patience and determination to work on modern cars today.
Congratulations!

What mileage should spark plugs be changed my 2013 sl500 has 8000 miles would you change them at this mileage

It's supposed to be 50-60k miles but I would change sooner because direct injection engines coke up their internals, especially with tuning that adds fuel; the only reason I changed mine is because Weistec recommended it for the tune - I will probably do changes every 15k on mine.

I have owned 6 brand new Mercedes and have always had the spark plugs changed at 75,000 miles with no engine related problems.