jorantes

I just bought an '03 ML350 w/ 65k on the clock, and the local MB dealer said the plugs needed to be replaced @ 60k and on his records they werent done... is he BSing me or what???

What mileage does MB reccomend to replace the plugs?

2bmj

My manual says 100,000 miles or 4 years whichever comes first.

mihir_d

First time ever. Dramatic improvement in mileage and performance...depending on the history of maintenance on the vehicle, I would say anytime between 75K and 100K is a good time.

Very expensive to replace though...usually about $200 in parts (if you get the plugs from the dealer) & $300 in labor...

newton22

If you're handy, do them yourself. Save a ton of cash and insure its done right. There are threads across the board.

mihir_d

https://mbworld.org/forums/m-class-w163/150974-maintenance-schedule-required.html

My post explains in detail the spark plug replacement with some pictures.

PaulX608

I'm at about 76k miles on my wife's ML430 and I'm getting ready to do this. Idle quality and fuel mileage is starting to diminish. I'm looking at about $320 for plugs and wires on the v8. I guess this is the only time I envy you guys with 6s!

mihir_d

I just did mine, and I am so glad I was dealing with only 12 and not 16.

Each plug will probably take you about half and hour or so to do...getting the boots out is the biggest pain of all..

BTW, you don't need to do the wires...there are plenty of internet website selling spark plugs for the ML, but I recommend you go to the dealer. Bosch assigns a special part number to the dealer sold ones, and I would guess those are the most correct ones to use on the ML.

They are pricey at the dealer, about $15/pop.

You are at the right mileage to do this. I too had noticed my mileage dimnish at around 75K miles. I even took it to the dealer and paid the $90 for diagnosis.

They attributed it to various factors spark plugs, MAF, exhaust (CATs), fuel filter and quoted me close to $3500 to replace all of that. Since the CATs were under the emissions warranty they did those for free. For all the other stuff, my SA advised me that since the Check Engine light wasn't on, I should just live with it and as the 100K miles approach start replacing all of this one by one.

The most noticable improvement in mileage has come so far with the plugs. This was my first project.

Next week, I have ordered the MAF and will do that.

And then two weeks after that its going to go to the dealer for the B Service and the fuel filter.

On a side note, I am also getting the entire drivetrain fluids flushed and refilled.

For all of
1. Transmission Flush/Refill
2. Transfer case Flush/Refill
3. Front Differential Flush/Refill
4. Rear Differential Flush/Refill

I was quoted about $450 at the dealership, which is really not bad.

I would advice people who are hitting the 100K miles to go for it. It is good preventive maintenance, and will certainly extend the life of the drive train considerably..

PaulX608

I'm gonna do the wires anyway. I already had one fail last year. Figure it won't hurt to change the rest now. They've been under there for 5½ years. Did the MAF last year, that should be good. Had my cats inspected about 1½ years ago when I got the recall letter. As far as the boots, I used the wrench trick I read about on here, and it worked very well. When diagnosing and replacing my bad ignition wire, I had 4 of the plugs and 2 coils on and off a few times. I'm sure it will be a more pleasant job than my fuel pump was.

PaulX608

I did my plugs this morning. Whew!! I decided against doing the wires at $240. I got the NGK G-power platinum plugs. Took about 2½ hours. Good thing I started at 0630! Man, 5 or 6 of those things are nasty to get at. I had very little trouble getting the boots off using the wrench trick I mentioned earlier, but they were tough to get back on all the way. Finally got the idea to take some silicone lube and a cotton swab to lube the rubber part of the interior of the boot. Voilla! Only had to remove 3 coils for space on the driver's side. All in all not the easiest plug change I've done, but far from the most difficult. I figure I saved $300 - $400 and the ML idles like an electric motor again. I'm sure the fuel mileage will come back as well. Bottom line, this is a reasonable DIY job if you're really handy. Make sure you have a selection of extension lengths, the amount of space varies a good bit from plug to plug. Good wrenching!

barijan

I just replaced my spark plugs and ignition wires today.
A 17mm open wrench is a must to pull the boots. There's a bent version of the wrench that makes things easier, but with some ability and patience you can use a regular wrench as well.
The access is easier if you remove the coils.

Two of the wires were almost dead, due to corrosion. As I had a complete set sitting around I changed them all, and keep the old ones that still good as spare.

It's supposed to be a half day job. I took some more time because I also resealed a leaky breater's cover.
I've found that some lousy mechanic damaged the border where the cover sits, probably hammered a screwdriver in there to remove the cover.
That's why the leak reappeared. Took me a couple of hours to repair it properly.

The spark plugs were terrible after more than 100k miles, and I noticed that they were the wrong type, a colder type, so they had many deposits on the electrodes.
Such plugs were so bad that I do expect a great improvement on the consumption.
Let's see.
Now... a deserved beer!

Kali86

Totally .. ml 550 .. seems hard to get at the last two back cylinders ... were u able to get your wrench back there ??