Spark Plug Removal

[dirtrack49]

Hello again,

Well, as I continue with the resurrection of my 66 230sl, it seems that everything I take a look at has it's own particular problem.

The last time this car might have been driven was in August of 2009. Prior to that, it probably was not driven since sometime in 2003. The last service of any kind was in 2003.

My new problem, are the spark plugs will not come out. I understand that these heads are aluminum and I am concerned with pulling out the threads if I apply to much force.
So far, I have applied PB Blaster to the plugs. I am only applying a little more force than normal as far as attempted removal without any success.

Should I use a small torch to heat up the head? Use a breaker bar, say 1/2 inch to apply a lot of torque?

I would attempt to start up the engine and heat up the head, only if I could assure myself that the engine is not frozen. When I get a vehicle that has been sitting for a long time, I always add top oil to the cylinders before attempting to start. Since I am unable to remove the plugs, I am wondering if there is another method that I might use?

Any and all help is greatly appreciated.

Tom L.

[menesesjesse]

Use the penetrant and be patient. I would use the breaker bar 1/2 type after the PB blaster.  As far as warming the engine i dont think this will help too much. Everything expands so expecting the plug to loosen is a long shot I think. The breaker bar shoul do the trick.
Regards

[jeffc280sl]

After penetrating oil I would try and get the engine warm and then invert a can of dust remover to spray the plug to cool it down.

[dirtrack49]

Hi Jesse and Jeff, I certainly appreciate your recomendations.

After some thought, I am going to try and get them out without attempting to start the engine. After all, the real reason I need them out at this point in time is to prepare the engine for start up and make sure I am not dealing with an engine that has seized from sitting too long.

My original thinking was that the aluminum head would expand more rapidly than the steel spark plug. I am guessing that using a dust remover would create a cold area at the plug?

What about heating the area around the plug with a small propane torch and use the dust remover to cool down the plug?

Call me paranoid, but I am a little concerned with the idea of placing to much torque on a plug that may be corroded into an aluminum head. Looking back on the limited service records that I have for the car, I can not tell when the last plugs were removed and replaced. It could be many years ago.

Tom L.

[DaveB]

Many times I've extracted stuck bolts by first tightening them fractionally then backing them out. I think that is worth a try first (you may have already). Heating around the plug with a small torch sounds a good idea as long as there's no fuel or excess penetrant around.
This stuck plug problem seems to happen a lot, my #6 is very tight. Rethreading with a helicoil or similar is a common repair.

[dirtrack49]

Thanks Dave,

After several days of penetrating oil (PB Blaster), I have finally got the #5 spark plug to come out. I first tried to tighten the plug and after that back it out. I found the threads to be in good shape and had no real problem backing out the plug after initially getting it to break loose. The plug is brand new. They must have been put in around 2003. There is almost no discoloration of the plug and the electrode is as new.

I ended up using a 24 inch breaker bar with a 1/2 inch drive and hex socket. I really felt uncomfortable putting that much torque to the plug, but I figured it to be my last resort. Unfortunately, so far, I can not get the other plugs to break loose. Either I will need to take the risk of applying more force, or keep working the penetrating oil.

Another thought is to leave the plugs in and attempt to turn the engine by hand, without the aid of using top oil in the cylinders.

Has anyone had experience with turning these engines by hand without the plugs removed? If so, should I expect a lot of resistance?

Seeing I don't have a shop manual yet for this car, can someone tell me the torque value in foot pounds for tightening the plugs?

TIA
Tom L.
66 230sl

[Benz Dr.]

You would be looking at 22 -24 ft lbs for spark plugs. I use nickel anti sieze on the threads.

  Why don't you remove the fuel injectors and squirt some oil through the holes. You will need to turn the engine over so the valves will open and let the oil run into the cylinder. Expect a lot of smoke when the engine starts.

 The main problem with removing anything from an aluminium housing is just how tightly the aluminium grabs. If you apply even preassure you will either break the screw off or round the corners off to the point you won't be able to grab it.
The trick with screws in aluminium is to shock them loose. I try heat on the metal parts only which will generally lessen the bonding. Giving it a quick snap or hitting the end of your wrench with a hammer can help. Penetrants are basically useless because you have two different metals that set up corrosion sealing off the threads. Using heat and then some penetrant while everythigh is still warm might work but don't count on t.

 The main thing is to use anti sieze on the threads and particularly around any places that have coolant running through or near the area you are assembling.

[dirtrack49]

Thanks Dan for the input.

Working with aluminum, I find, can be somewhat difficult at best.

So far, as of today, I have gotten number two through five to submit. For some unknown reason, number one and six do not want to give in.

It seems that applying torque to tighten, prior to attempting to loosen the plug, appears to work. How much the PB Blaster does is a great unknown. I know from past experience, that the PB Blaster seems to do a good job with anything that has to do with corrosion. However, in this situation, it is hard to tell if there is any benefit to its use.

I am going to let number one and six sit for another day, apply some impact to the outer portion of the plug, and try again. If that doesn't work, I will inject the cylinders through the fuel injection ports as you have suggested.

In any case, if I get the plugs out, I no doubt need to get some lubricant up into the valve train prior to initial start up.

Thanks again,
Tom L.

[lurtch]

Hey Tom - - -   here is my two cents worth.

Put an impact rated socket on the plug, but turn down the pressure to your impact gun until it is just lightly tapping. Then be patient and let it hammer away lightly, until you think you can step up the pressure little by little.

If the threads are truly seized permanently (this is unlikely) you will have to remove the head and have a machine shop use a process called ELOX, short for electrical oxidation.

Larry in CA

[dirtrack49]

Thanks everyone for your input.

I finally got all the plugs out!

I believe it was a combination of PB Blaster soaking away for several days,  light tapping on the plugs with a socket and hammer, and a lot of brute force. I also tightened each plug down a little more before exerting a lot of torque with a 18 inch 1/2 drive breaker bar.

The reason I felt that the PB  Blaster may have helped, after extracting the plugs, there was oil on the plug threads. This oil must have penetrated to the threads since I had cleaned up the head before removal of the plugs.

After putting top oil in each cylinder, and spraying top oil under the valve cover through the oil filler, I was able to turn the engine by hand. Actually, I don't believe the engine was every seized since I did not let the top oil sit for any lenght of time.

Thanks again for everyones help and on to the next item.

Tom L.

[Benz Dr.]

There's a recess at the base of the spark plug where any oil can sit. As you were removing the plugs that oil ran down and around the plug threads. The gasket on the spark plug is there to provide a positive seal so that no cumbustion gasses escape - nothing will enter either. A regular screw with a washer won't seal as well and you can expect some creeping of oils but anything with a seal ring virtually prevents this from happening.

  However, you were able to remove them and that's what counts.

[dirtrack49]

Dan, that makes perfect sense to me. I was also wondering how the oil could penetrate a plug that has a seal. Now it is obvious to me what really took place when the plugs were removed.

Thanks for the info.

Tom L

[ejboyd5]

Patience is its own reward - good job on the removal without breaking anything.

[J. Huber]

Hello all. Nothing to add to the existing thread -- its just that the subject line is perfect....

So I am planning a plug change and cannot remember: remove them cold or when warmed up? Or does it matter?

[jacovdw]

James, spark plugs are best removed when cold... 

[J. Huber]

Thanks Jaco!!

[Shvegel]

Named for Greg Peterson one of the mechanics in a shop I worked in years ago the Peterson Principle of Applied Torque has been an invaluable too over the years. Greg believed that you were more likely to  break or shear fasteners by slowly applying torque so he would use as much torque as fast as possible. Stuck drain plugs and spark plugs were treated to a blast from a good 1/2 impact gun. Funny thing is it works and works well. About 10 years ago I was a foreman in a Saab dealership and one of my guys was having trouble with a stuck spark plug on an old car. He was just about to just leave it alone and tell the customer when he broke the insulator off the plug. So he's standing there, the customer is in the waiting room and the plug is broken off. He looks like he wants to die so I walked over with my impact gun, Told him to stop screwing around, leaned under the hood, paused for a second to take in his look of horror and pulled the trigger...Popped right out. 

[Benz Dr.]

Named for Greg Peterson one of the mechanics in a shop I worked in years ago the Peterson Principle of Applied Torque has been an invaluable too over the years. Greg believed that you were more likely to  break or shear fasteners by slowly applying torque so he would use as much torque as fast as possible. Stuck drain plugs and spark plugs were treated to a blast from a good 1/2 impact gun. Funny thing is it works and works well. About 10 years ago I was a foreman in a Saab dealership and one of my guys was having trouble with a stuck spark plug on an old car. He was just about to just leave it alone and tell the customer when he broke the insulator off the plug. So he's standing there, the customer is in the waiting room and the plug is broken off. He looks like he wants to die so I walked over with my impact gun, Told him to stop screwing around, leaned under the hood, paused for a second to take in his look of horror and pulled the trigger...Popped right out. 

Yeah that works. I also saw someone get fired for using the same method to install them.

[ja17]

I always had better luck removing the spark plugs from a warm engine.?

[66andBlue]

You would be looking at 22 -24 ft lbs for spark plugs. I use nickel anti sieze on the threads.
.....
 The main thing is to use anti sieze on the threads and particularly around any places that have coolant running through or near the area you are assembling.

Hi Dan,
I have always followed this advice and religiously put anti-seize on the threads, whether new or old plugs.
Well, today I received new NGK plugs with the warning (attached  below as a PDF) not to put any on new plugs with special metal plating, that is, plugs for aluminum heads.
Only used plugs without metal protection remaining should be treated with anti-seize.
Here are additional torque specs:
http://www.ngksparkplugs.com/tech_support/spark_plugs/installation/index.asp?mode=nml