CHB

When tightening them, how tight should it be? As tight as I can, or when I think they are tight enough? I'm afraid of overturning and damaging the block

clkguy

first, always put a dab of anti-sieze on threads, then finger tight plus a 1/4 turn, they have a crush washer at the seating surface that creates a seal

Kestas

For reference, my E320 specifies 18-22 ft-lbs to install. This is in an aluminium head. Ditto on the antisieze.

levelr123g

i would NEVER use antiseize in the plug threads. there is no reason for it.

mleskovar

Why would you say anti-seize is not needed on a steel spark plug going into an aluminum head? Everything I have read says to use it, but sparingly. Stripped spark plug hole threads in aluminum heads is not a myth.

Kestas

There is PLENTY of reason for using neversieze.

I suppose you've never read the many posts on automotive forums where people have had the spark plug break off flush in the head, nor personally experienced the pleasure of removing a bolt frozen in aluminum only to follow up and fix the problem with helicoil inserts, nor realize that galling of fasteners in threaded aluminum holes is a well-documented problem in technical journals.

A jar of neversieze is a must for any toolbox and is highly recommended for use on any fastener threaded into aluminum. This stuff has made my life a lot easier for the 20 years I've been using it.

What I DON'T recommend is for people to overapply the compound or add it to a fastener that already has some of the compound dried out and caked from previous applications.

clkguy

as seen here anti sieze is a MUST for ease of removal, do to the aluminum and steel plugs expand at different rates and causes the plug to like lock itself in the hole and a few other reasons,so if you have been told otherwise, seek another source of advise

CHB

I asked my MB tech guy, and he said that they dont put anything on the plugs, they just change em. He also said that they put them in by hand, and dont use a torque wrench.

Steve Clark

your sparkplugs are going to be in there a long time.The OEM Bosch plugs that the dealer's shop installs come with an anti-seize coating.
While it's true that the steel sparkplugs and your aluminum heads expand at different rates,that's not what makes the plugs stick.Aluminum expands with heat about twice as fast as steel-it gets looser with heat,not tighter.The easiest way to get a seized sparkplug out of an aluminum head is to do it while the engine's hot.
What can happen is that combustion products will seep into the small gap where the threads are.It can cook into place and solidify like cement.Not "will",but "can".Modern engines have cleaner combustion and aren't as prone to do this.It still can happen.
It's advisable to put a small dab of never-seize on threads @ installation.Run it in finger tight,then go 1/4 turn more,just like it says on the box the plug comes in. You only need a torque wrench if you're putting the same plugs back in again.

CHB

Is this anti-seize coating visable, because i cant see it. So you advise I still put some never-seize on it? Thanks everyone for your help so far

Steve Clark

won't hurt anthing.Be aware that more is not better...Some varieties of anti-sieze will kill your O2 sensor if you use way too much,so just a little smear on the threads is all that's necessary.
The coating that Bosch puts on their plug threads is very thin.It's apparently some sort of proprietary coating.