spark plug changing virgin
 

I am getting ready to do the spark plugs on my m119 w125 400e, which i have never done before. on any car. I am taking the opportunity of owning a 16 year old car to learn how to do a few things besides an oil change.

Any tips?

I know about getting the right plugs (non-resistor, right spec etc); i am getting the BOSCH f8dc4.

The wires look good and are in spec.

I guess i will borrow a torque wrench from autozone or perhaps my neighbor. or buy an inexpensive one.

I assume i put anti-seize on the threads and di-electric grease for the boots and go one plug at a time...but i also understand the anti seize affects the torque. any advice.

anything else i should know about?

Don't use anti seize. The factory didn't use it, neither should you.

The only advice I can offer is to install the new plugs by hand to make sure they do not cross thread. Torque to proper specs, which I don't know offhand.

I disagree. Unless you know that the new plugs have an antiseize coating, a thin coating of antiseize should go on the threads. Steel threads in any aluminum hole should get this treatment. There are too many documented cases of stuck plugs in aluminum heads to push this step aside.

Otherwise, yes to the dielectric grease and hand-starting the threads.

Removal may be tricky. Twist the boot to break the bond to the ceramic before pulling. When pulling you have to grab the boot at the right spot so the wire doesn't come off the terminal. Consider investing in a special wrench for this. Use two hands to unscrew the spark plug, as you don't want to bend the spark plug and break it.

Torque is tricky. Because of the antiseize I torque to feel. Snug may be the word to describe it.

Best tip you'll get is to get someone who's done this before to be there with you. Do you have a local MBCA chapter?

my wires have what I would describe as plastic "handles" on them, sort of mushroom shaped with the wire going into the center. not sure how i would get a spark plug puller around them. i pulled one and it came out pretty easily.

thanks of the tips thus far

The rear spark plug on the passenger side is a bit hard to get to, but access is improved by removing the wiring harness clamp that's in the way. Take out the allen bolts (can't remember if it's one or two) and just pull the harness over a couple of inches. If your wiring harness is original move it with the care due a frail $500 part.

I always use a small amount of anti-seize no matter what I'm working on. I have good luck with it--makes changing them again that much easier...

-GH

thanks everyone. 5 out of 8 done.

the 2 wires on the passenger side and the last one on the drivers are hard to get to...i have to go buy a shorter extension to even get the wrench in there.

i loaned a torque wrench from autozone, and tried to use it but it seems to not to click even when the bolt seems super snug...

I am using anti-seize.

how tight do the plugs need to be on there? right now since i dont trust the torque wrench i went to "snug"...ie, i could probably get them tighter if i threw my weight into it but not simply using the wrench and arms.

on removal the ones of the passenger side seemed tighter than the ones on the drivers. really had to work to get them off.

good news is that while they need to be replaced, they show normal wear and evenly worn...we will see about the last three.

My experience exactly. Hence the reason I suggested not to use a torque wrench. It sounds like you got them tight enough. You don't want to strip the threads from overtorquing. Unfortunately you can only develop a feeling for proper torque from a lot of wrenching experience. Otherwise I use a torque wrench wherever it's required. Good luck.

You can use a length of rubber fuel line fitted over the end of the plug to thread the plug into the spark plug hole in hard to reach plug holes. It will will allow the plug to run into the hole without the danger of an extension and socket starting a cross thread problem. Good luck

Done!
 

Okay, got the short extension and a BEAM torque wrench...which seems to work better...at least i get a reading of some sort on it though i trusted the feel more than the reading. Mainly i checked the one bolt i used the other torque wrench on. anyway, its long handle came in handy on the last on on the passenger's side...what a pain it was to get that one out. really tight...the new one went in no problem though.

turned it all on and ta da! it actually worked. seems to run well.

though i think my engine mounts are getting old...i think i might leave that to the mechanic. the car vibrates a bit as the rpms get higher.

anyway, thanks for all your help. it took 3 hours i guess from start to finish of actual labor, including snags.