there is a lot of
talk about these spark plug lubrication. Some say it must and others say
antiseize must not be applied.
My personal idea is to use ceramic antiseize or Molycote TA on the threads of the spark plug. Especially since the repair of the head is awkward. The process of putting in a spark plug us such that you turn it snug, and then tight with 25Nm.If the 25Nm can not be verified, a rule of the thump is a quarter turn since the plug is seated flat with a crush ring. This crushes the crush ring, assures proper seating and avoids turning loose after a while.
The manual says to coat spark plug threads with Molykote HTP, but I don't have access to any. I have on-hand both Loctite anti-seize stick Silver and also Versachem type 13 high temp copper formula. Can I substitute either of these for the Molykote HTP?
The rule of thumb seems to be nickel based anti-seize for Fe-to-Al or Al-to-AL while the copper based stuff is reserved for Fe to Fe only. The copper base stuff will cause corrosion when in contact with Al.
Hope this helps.
Instead of just changing my spark plugs tonight, I have been surfing the interweb looking for a decent explanation of why there are so many different types of anti-seize formulations, and how to figure out which formulation to use in which application. I am not an engineer and have never dabbled in this, so what I found out will be no surprise for those in the know.
Anti-seize compounds are used to prevent a chemical reaction between the two materials being screwed/bonded together. The composition of the materials, along with the expected heat levels, dictates which anti-seize compound should be used.
copper-based should be used in steel to steel applications
zinc-based should be used in steel to aluminum applications
This explains why Porsche specified Molykote HTP (which is zinc based) for the spark plug threads.
However, Molykote HTP is expensive and difficult to obtain in small quantities. From what I have seen, I think that the best replacement for Molykote HTP is to use Loctite 39901 Zinc Anti Seize Compound.
Does this make sense to anybody?
To throw a wrench in the thread, I recently read this in a 911 engine rebuilding book.
"Porsche doesn't recommend the use of anti-seize compound, as detailed in Porsche Technical Bulletin 9102, Group 2, identifier 2870. The bulletin applies retroactively to all Porsche models and the theory is that the anti-seize tends to act as an electrical insulator between the plug and the cylinder head".
After reading that and doing some research I have found that spark plug manufacturers don't suggest the use of anti-seize as they have anti-seizing compounds built into the metals of modern day plugs that negates the need for anti-seize.
Good point. Here's a case:
I was working on an '85 928 last Summer and six plugs came out fine. They looked to have anti-seize on them. One was tough and one was nearly impossible. Those looked to have no anti-seize. Once broken loose they needed to be worked back-and-forth as I could feel them galling up.
I always did it before and this reinforced always doing it.
I don't put any goop under the washer or the plug bottom. That'll leave more than enough area to conduct the spark. Consider that the wire has a tiny cross-section. A spec of contact is good enough and the area between the plug bottom and the head is probably 100x the size.
can you get away with out the antiseize on the threads, maybe.
Does the plug come out of the hole better with antiseize, usually it does
Does antiseize work to prevent the threads on the lug bolts from getting damaged, yes it does.
If your not interested in using the antiseize on any threads have at it.
I will always check the plug gap and then put a smear of antiseize on the plug threads, I have not ever had any thread related failures using this process, i find that the plugs do unscrew easier than uncoated plugs, I believe that the antiseize also assist in preventing the combustion products from filling in the rear sides of the plug threads , look at the next set of plugs that come out , if they are all coated with dark brown deposits up to the sealing ring this is whats happening, and i am not talking about oil filling the threads
I've used plain old silver anti-sieze on plug threads since just after I seized a plug and pulled the threads out in an early 911 motor. Just on the threads starting one or two from the end, nowhere near the tips.
On the lug bolts, the WSM is specific about using it on the tapered/cone part to prevent galling between the cone on the nut and the cupped surface in the wheel. I don't put it on the threads generally.
Dr Bob, '89 S4 Auto, black
From page 44-19
"Lubricate threads and Calotte with optimoly TA"
Jon in OZ
Here is what Autolite says about using anti-seize (snicked off the net somewhere):
We do not recommend the use of any anti seize products for installing spark plugs. Anti seize compounds are typically composed of metallic,
electrically conductive ingredients. If anti seize compounds come in contact with the core nose of the plugs, it can lead to a misfire condition.
Anti seize compounds can also have a torque multiplying effect when installing plugs. This can lead to thread distortion and thread galling
resulting in cylinder head damage. Autolite spark plugs are nickel plated to resist the effects of corrosion and seizing. However, plug seizure is aggravated further when steel plugs are installed into aluminum cylinder heads for a long period of time.
Here's what AC/Delco says:
Do not use any type of anti-seize compound on spark plug threads. Doing this will decrease the amount of friction between the threads. The result of the lowered friction is that when the spark plug is torqued to the proper specification, the spark plug is turned too far into the cylinder head. This increases the likelihood of pulling or stripping the threads in the cylinder head. Over-tightening of a spark plug can cause stretching of the spark plug shell and could allow blowby to pass through the gasket seal between the shell and insulator. Over-tightening also results in extremely difficult removal.
If you decide to use anti-seize, you should reduce the torque value by 20%.
Btw, I am not advising NOT to use anti-seize, I am saying that I believe a properly torque spark plug is much better than a over torques plug with anti-seize.
For your reading pleasure, here are some previous antiseize threads I've collected, with quotes from some of them. Sometimes I wish there were only one answer.
Special antiseize for lugs etc...
From the 1986 booklet of service info by year:
Wheel Nut Treatment on Aluminum Rims
If wheel nuts are lubricated with the wrong type of grease prior to installation or even installed dry, the spherical calottes of wheel nuts could seize in the countersunk holes of the rims. The factory is using OPTIMOLY TA paste successfully at the present time.
This lubricant is available in 150gram tubes for Service (Part No. 000.043.020.00).
The tightening torque for wheel nuts is still 130 Nm.
Lots of interesting reading in this series of booklets, available in Jim Morehouse's CD set.
Here is more info than you ever wanted...
Copper Anti Seize Compound
Part No. 2012
I still have a tube I bought from Devek when I bought the wheels for the 79. I use on both cars and still have most of the tube left. Here's a link to what it looks like.
Here is the MSDS sheets for the Optimol TA which lists composition of ingredients that could be compared to similar products.
I also have problems with graphite and aluminium due to the corrosion.
I was involved with the building design and building of 7 LNG Carriers, 125,000 cubic metres of LNG per voyage and the 4 cargo thanks were 40 metre internal diameter Moss Rosenburg aluminium tanks, no graphite and no carbon was allowed anywhere near the tanks due to carring temperature of -162 degrees C (expansion and contraction) and any imperfections were limited to 0.2mm IIRC, so I have a healthy respect for not using graphite on aluminium especially in high stressed areas.
When I replaced the first set of spark plugs on my car over 9 years ago I put the RACOL anti seize on the threads of the plugs and torqued up.
After installation I remembered graphite and aluminium. Next day down loaded the MSDS for RACOL and no graphite of carbon content, so all was OK, so I would have some concerns with Optimol Paste TA with 10 to 20% graphite content.
Tails 1990 928S4 Auto
... and providing the following links for reference:
Bill ball posts 4/85 Tech Bulletin on lubing wheel nuts