aubrey993

Changing spark plugs on my 1997, 993, I have 1 plug that is very tight. I've managed to slowly remove it about half way, but now I am concerned about stripping threads in the head. It's very tight making it difficult to even tighten it back down. Any recommendations on continuing to remove it? Has anyone had a similiar problem? How do you overcome this dilema?

Agro1

I would be more concerned with breaking the spark plug itself rather than stripping the threading on the head...Getting some heat on it may loosen it up a bit, but I'm not sure how you could apply heat (without running the motor and you can't do that missing a plug). Make sure you use anti-seize on the plug threads when you put the new ones in...If it were me, I would very, very slowly apply gradual torque to the plug and try to back it out, but then again you may break it...It may just be hung up on an irregular thread.

mike cap

Aubrey,

There's nothing you can do coming out other than soak the threaded area with penetrating oil now and carefully continue to back it out. If the plug was cross-threaded it was done on install and you're not going to do any additional damage coming out. The threads can be cleaned up once the sparkplug is out.

Just be concerned now with not "rounding off" the flats on the plug by whaling on it with a breaker bar. I would use a 6 point socket, not a twelve point, for better contact area - you need every break you can get right now.

Inspect the plug after removal and you can carefully run a thread cleaning tap through the spark plug hole to restore the threads. Use compressed air to keep the threads clean and penetrating oil for lube. This is a finesse job and you're working blind, so if you aren't comfortable find a machinist or tech to help you out.

Agro1

Well said, Mike, good tip on the penetrating oil...Finesse job is an understatement...

JM993

I hope this is one of the "easier" plugs and not the one under the power steering pump!!!!!!!!!

Greg Fishman

Never use anti-seize on the spark plug threads per the workshop manual.

aubrey993

Thanks for the advise so far, Mike and Joe. It's one of the easier plugs (lower rear passenger side). I'm using a six point socket and a standard length ratchet, no breaker bar yet. Worried about applying too much torque.

Thanks Greg for the note about anti-seize. I was not planning on any, as per the manual.

Ron

Greg,

I know the workshop manual says that and when I changed my plugs I did not use any anti-seize, but it seems like it would be a good idea to use it and I know of at least one independent Porsche shop that recommends anti-seize on plugs.

The plugs are not torque that tight if done properly, like 25 nm. But it just seems like anti-seize would be a good idea.

I recently had to do some exhaust work on one of my Mercedes vehicles and I used this product called VersaChem type 13; it's an anti-seize lubricant that is "sensor safe". It's a hi-temp copper based product that resist temps to +2000 degrees F.

Maybe Porsche doesn't recommend anti-seize due to conductivity problems. If so wouldn't a copper based product nullify that concern?

Greg Fishman

I don't know if anti sieze was the problem or not but I have had two spark plugs work themselves loose on my race car. The threads were gummed up with antisieze so I figure that was the problem. I cleaned the threads and re-installed without anti sieze and have had no problems since.

Maybe Steve W. can clear this up. He has probably installed a few more spark plugs than most of us here.

chris walrod

From what I understand, anti-seize (while designed for anti-galling and fasteners of different materails, heat etc.) is not recommended by Porsche due to grounding or conductivity reasons. The high energy ignitions of the 993 requires the best possible grounding.

For the stuck plug, try some type of penetrating oil and turn it clockwise every so often, trying to breakfree what ever is holding it up. I was thinking maybe some carbon was hanging it up. Now if its been cross threaded in the past, there is not much you can do at this point other than just carefully turning it outward..

Good luck!!

Agro1

I seriously doubt the workshop manual was written with "Race" cars in mind...And I doubt the workshop manual recommends removal of the engine tray, but I bet you removed it from your race car, right ? Point is, the workshop manual is not gospel and there are better ways to do things. Furthermore, a plug that has been cross threaded would benefit greatly from a small dab of anti-seize...As Ron stated, I also know of a few independent race shops that use anti-seize on their plugs...

chris walrod

When I replaced my plugs last year, it was difficult for me to install them dry as I have always used some type of anti-seize on fasteners of different materials. Especially in a 'hot' application. Too many people warned me against using anti-seize on late model P-cars..

Now keep in mind over-tightening spark plugs in aluminum heads, especially if torqued while the engine is still hot, is what leads to trouble in removing them at a later date..

This is a touchy and debatable subject..

Agro1

I wouldn't suggest replacing plugs on a hot motor...first of all, by the time you get the right side disassembled, the motor ought to be pretty much cooled down. That's assuming you change EVERY plug and not ignore the hard ones...Torquing plugs into a hot head that has not had time to suffeciently cool and contract may be the reason people's plugs get "Stuck"...Since there is not enough room to properly torque each plug, overtightening it in a hot head could be bad news down the road. Hand tight plus another quarter turn is the rule of thumb when the motor is cool. That way the plug can expand and contract at the same rate as the heads...

Greg Fishman

But the manual doesn't state that you should never remove your engine undertray. It does state that you should not use anti sieze on the plugs. That is the difference. If you cross thread a spark plug what good is a bit of anti-sieze? You need to run a tap through the head to fix the threads.

Agro1

Greg - yes, the workshop manual specifically says not to use anti-seize, but I'm sure there are other things the manual says not to do that many HAVE done with no ill effects - Like when I used anti-seize on my 60k service. Haven't had a problem since and I've re-check the torque specs on the left hand side, nothing has moved.
If a thread were cross threaded and anti-seize used when it was installed, it would make getting it out a bit easier...Either way, I think the point is that Aubrey just needs to back it out gently since there really is no other option...