Replacing Spark Plugs on ML 320 (2000)
 

I'm thinking about changing the plugs myself, I heard that I need a special tool to disconnect the wires....is this true? What are the best plugs to put in?

http://www.keysolutions.com/M-Class.nsf/Home?OpenFrameSet&Frame=Main&Src=%2FM-Class.nsf%2Faac7d56ca8fd884b852563be00610639%2Fb8a89966a39517fc85256e1800137e98%3FOpenDocument%26Aut oFramed :thumbsup2:

The linked writeup describes the tool requirements nicely but contains two serious errors.

1. DO NOT put antiseize on plug threads. Mercedes, Bosch, EVERYONE says don't do it. It makes a mess and encourages stripping threads, as the plugs will end up overtorqued as lubrication eliminates ability for torque wrench to provide correct specified reading.

2. DO NOT use KMart platinum plugs as shown, but rather use ONLY the original specification plug, as noted in owners manual.

There is zero/zip/nada 'mericun shadetree mekaniken knowledge that can supercede Mercedes engineering.

Standard 17mm combination wrench worked for me (mine are Craftsman).

Tip: Stuff an old bath towel down along the inner fender (under the plugs). When (not if) you drop something like one of the new plugs, it will land on the towel instead of going into the inaccessible bowels of the engine compartment.

This was very useful as a buddy of mine asked me if I can do plugs and wires on his 2002 ML320.

Again this forum has provided to be a very good information source.

I finally did the plugs in my friends ML 320 last night. He had 120k miles and still the original MB spark plugs. Half the electrodes were worn completely down and it sounded like it was running on 4 cyls.

This was not as hard as a job as some people let onto. I took my time and did the drivers side first to get the hardest side out of the way. I think it took about 1.45 hours to complete the plugs and wires. After doing the drivers side I realized that with each coil pack, the top plug wire went to the front plug and the bottom wire went to the rear plug of that cylinder. So, on the passenger side, I just moved all three coil packs, pulled all 6 plug wires (after figuring which ones were the longer ones) and then all 6 plugs at the same time. I did the Passenger side from start to finish in 30 minutes. And I didn't cut my hands on the manifold covers!

A little dielectric grease on either end of the plug wires for protection and for ease of removal later and I was good to go. The best tip that was given was to stuff a towel or old clothing between the exhaust manifold and the inner fenderwell. I dropped one of the coil screws and it saved me from having to fish it from the frame rails under the engine.

Here is also another tip: Make sure when you are putting the engine cover on you do not push it all the way back to line it up. You may knock the vacuum line to the brake booster back out of the manifold. When we started the truck after the plugs were done, it ran like junk. I could hear a colossal vacuum leak. I started to feel around back there and once I moved the vacuum line and heard it stop leaking, I knew I found the issue. I simply pushed it back into place and vacuum leak stopped and the truck ran well.

Thanks again to everyone for their advice.