A brief guide on how to change the spark plugs on an M113K (55K) engine found in the E55 AMG and CLS55 AMG and others.
What You Need:
- 16mm Spark Plug Socket
Sealey AK6557 Spark Plug Socket 16mm 3/8″Sq Drive Thin Wall
- Wrench and short extension bar set
Draper Expert 71244 71-Piece Metric/AF Vortex and 1/4-Inch and 3/8-Inch Square Drive Gear-Ratchet Combined Socket Set
- T30 Male Torx Bit
Male / Female / Torx / Star / Tamperproof E Type Sockets 3/8 Drive 34pcs AT447
- 17mm Open Ended Spanner
Silverline 380248 Open Ended Spanner, 16/17 mm
- 16x Spark Plugs (OEM is NGK Iridium ILFR6A 3588):
Spark Plug for MERCEDES BENZ CLS55 AMG 5.5l 5439cc from 1 / 2005 onwards 3588 ILFR6A
1. Remove the Air Intake Assembly
The air filters and intake pipework come off as a whole piece.
First, lift off and unclip the front engine cover (the one with the Mercedes Star – it has already been removed on the picture below). There is a clip on each side that will release and it will detach.
Next, pull out and remove the two big black intake pipes that come up to each side of the intakes.
Unclip the central air intake at the rear of the engine. There is a single clip that holds this in place and once rotated slightly, will allow the whole intake assembly to come off. Each air filter box (one on each side of the engine) comes with it and they can just be pulled off. They clip onto some rubber mounts.
It’s probably worth changing the air filter elements at this point – they are cheap and you already have the air boxes off! You can remove them by undoing the T25 torx screws around each box and lifting off the covers.
2. Remove Ignition Coil Packs and Leads
Each spark plug has an ignition lead connected to an ignition coil which are mounted to the engine by T30 Torx screws. Each ignition coil assembly has two leads (for two plugs) giving 4 in total for each side of the V.
Pull each lead from where it connects to the spark plug contact underneath the ignition coil. They are quite hard to unplug and come off with a pop. I managed most by hand but you can use a 17mm open ended spanner to lever them off.
Disconnect the electrical connectors at the top of each coil pack and remove the T30 screw.
Important: Remember the order the ignition leads have been removed. They are marked with letters which correspond to the embossed letter on the engine cover. They must be re-connected in the same order.
I laid the ignition coil packs on the top of the engine in the correct order while I removed the spark plugs in turn
3. Remove the Spark Plugs
Use the spark plug socket and small extension bar to get under the rocker cover and into the recess where each spark plug screws in. There isn’t much space – especially as you get towards the rear of the engine) but undo each plug in turn and remove them from the engine.
You can see the old plug and the new plug. Not bad for 70k miles – still the original plugs and didn’t need changing but I wanted to do them for peace of mind.
4. Insert the New Spark Plugs
Add a little bit of copper grease to each new plug to prevent any seizing in the future and use the same socket and bar to screw them in. If you have a torque wrench, they are done to 25Nm.
5. Reconnect Leads and Install Air Intake
Now is a good opportunity to give things a good clean under there – once that’s done, reconnect the ignition leads firmly, in the correct order. You will hear a click/pop when they area seated properly. Re-attach the electrical connector the the top of each ignition coil pack and secure them back onto the engine with the T30 screw.
Reinstalling the air intake is the reverse of the removal. Clip the central intake pipe back on to the rear of the engine head until it clicks into place. Each filter box should be pushed down gently onto the rubber mounts until they clip in place too.
Reconnect the large black intake pipes to both sides of the intake and you’re done!