Spark plugs removal

[jmvsl]

Hello all, I'm new to the club,  I have a 1965 230SL, I wanted to replace the spark plugs but I was able to remove the front one and the last one, the 4 middle ones don't turn, I'm afraid of too much force may brake them...  the vehicle is running ok but I do not know when was the last time my Dad, replaced them and he is no longer arround to ask  :'(...  any tips on how to removed them?  ultimately the local mercedes dealer will service it; but I would like to do it my self.  please advice.

Thanks

[ja17]

Hello,

If they are stuck, try to remove them with the engine hot and get a bigger handle. Leaving them in will only make it worse later. Be careful not to cross-thread them putting the new ones in. Start them by hand if you can before using tools. A small length of fuel hose on the top of the plugs is a nice tool to start them without danger of cross threading.

[Richard Madison]

If other suggestions don't work:

The key is leverage. Use a long socket rod (maybe 12 or 18 inches). Fit a socket wrench to the top of the long rod. Then put a hollow pipe or similar over the socket wrench handle to increase its effective length.

Push the plug end of the long rod firmly against the plug base, then raise (turn) the pipe extender in the loosen direction.

Maybe some WD40 will help (careful if the engine is hot).

To prevent tight plugs in the future, before installing a plug put some Anti-Sieze lubricant on the plug threads.

Richard M, NYC

[al_lieffring]

I have found that when removing any steel threaded object from aluminum; bolt, spark plug, whatever, applying a frim constant presure on the wrench handle will work better than twisting with ever increasing force untill BANG it pops loose. Also use the shortest possible extender bar between the socket and the handle, long enough that you can turn the handle clear of obstructions but short enough that you don't loose force form the torsional felx of the extension bar. Put a cheater pipe on the handle only as a last resort.

 

[jmvsl]

Thanks to all I ran the engine for 15 minutes and a longer range worked...  thanks  I have new plugs now.

[Shvegel]

Hi,
I applaud your efforts to do it yourself but unfortunately I would recommend that you let a professional handle this.  Speaking as someone who has over 35 years behind a wrench there is a "Feel" that you develop that lets you know how hard you can pull before you tear the threads out of the cylinder head or brak off the plug in the head which is much worse since drilling out porcelain is a virtual impossibility.  Everyone has their favorite method for removing frozen spark plugs. Personally I am a devote' of the Greg Peterson principle of applied torque. Greg was a co-worker of mine who believed that you should apply as much torque as quickly as possible which hopefully breaks the plug(or bolt) loose before it gets a chance to twist to the point of failure. He used to use a 1/2 inch(13mm) impact gun and a socket and just pull the trigger.

Another thing to consider is if it is running well and you really don't plan on putting too many miles on it just leave it.

[Naj ✝︎]

So, what is the rule on tightening new spark plugs?

A Bosch trained mech I knew would tighten new spark plugs (by feel of course) and loosen them by a couple of turns and then retighten. This was done to crush the new sealing washers. Saidd it was always easier for removing the plugs the next time. True?

naj

[jmvsl]

The new ones I installed (BOSCH platinum) they recommend to tight them to 12 lbs...  that is what I did.

[waqas]

The new ones I installed (BOSCH platinum) they recommend to tight them to 12 lbs...  that is what I did.

The recommended plug is either the Bosch W7DC (or W8DC/W9DC), or the NGK BP5ES. I've used both with excellent results. I've never really tried out the Bosch platinum plugs in these engines... if you want more details, there are lots of discussions about plugs-- use the search function.
Also, the Technical Manual has some info: http://sl113.org/wiki/pmwiki.php?n=Electrical.SparkPlugs

I always tighten plugs by feel. I don't really trust my torque wrench for small torque values... don't forget anti-seize on the threads!

[jmvsl]

The one I installed is the BOSCH WR7DP, so far so good, they worked ok so far but only have put on like 10 miles and when we get better weather I will do more driving and report again.