99.9% sure I cross threaded a spark plug
 

I got my fuel injectors back from WitchHunters, and except for one that was fair the rest were in good shape (see this thread http://forums.pelicanparts.com/porsche-911-technical-forum/411253-bad-valves-guides-bad-fuel-injectors.htmlfor fuel injectors).

I reinstalled them and then proceeded to reinstall the plugs. Everything was fine until I got to #3.

I felt the resistance way too soon so I backed it out and tried again-same resistance way too soon. Eyeballing the Porsche spark plug tool and I could tell it was sitting too far out of the hole. I switched to another plug in case that one had bad threads but no joy. I put the connector on the plug and the round rubber flap doesn't even touch the valve cover.

Sooooo....what do I do now? Should i just finish screwing it in the rest of the way and save up for a head removal/drill down the road? How much would the head work cost just for machine work if I removed the head myself and drop it off?

While searching the internet I found this tool, http://toolmonger.com/2007/11/14/un-oops-that-cross-threaded-spark-plug-hole/. It supposedly can fix that cross-threaded hole from the inside — without pulling the head.

Man if it wasn't for back luck I wouldn't have any luck.

I think you need to have it repaired by someone who has done such a repair before. You don't want to have to get into worse and more expensive repairs. Don't beat yourself up too much, we all make mistakes at times.

Dude,...I have a crossed #1 since purchase,..really pisses me off to do my "5 plug changeout"..... I've had my P-wrenches attempt extraction to no avail (and they didn't break it off!!!!!!!)...sounds like yours could be corrected with the proper thread correction tool (possibly?) since it's an insertion issue...One thing's for sure.....I'd let only someone experienced frick with it,..mine? looks like and engine drop and timecert..... will be a task for someone else ,.. not me.

for your reading pleasure:

http://forums.pelicanparts.com/porsche-911-technical-forum/341869-fear-loathing-1-spark-plug-trail.html

http://forums.pelicanparts.com/porsche-911-technical-forum/361498-how-long-should-i-run-stuck-1-plug.html

Others will chime soon with specific instructions....

Best of luck to you,

A heli-coil repair is very reliable, simple, cheap and quick. I would guess you would have to remove the head, but ask your machine shop first. I watched a friend do it on one of my motorcycles and we didn't pull the head - of course access was much better than on a 911 engine.

I haven't done this on a Porsche engine but what I have done in the past is to remove the exhaust manifold and fabricate a block off plate with an air fitting for compressed air on the cylinder you are working on.

Then rotate the engine so the exhaust valve is cracked open and while preventing the engine from rotating connect the air hose so air is being forced out of the spark plug hole. You don't need a lot of pressure, just enough to keep any chips from falling inside. Then with a well greased tap, re-tap the hole.

Remember to always back the tap a half a turn for every full rotation. Also, remove the tap every couple of turns to clean and re-grease it.

I did this on a bmw m3 engine and the results were excellent. I also checked inside the cylinder with a bore scope and it was very clean with no traces of chips inside.

Hope this helps.

-Adam

I started to do a Google, but I'll let you finish it. There must be by now someone who has devised a tap that expands once inserted into hole and then backed out, or reverse tapped. I can see the device in my mind plain as can be.

Of course no. 3 is very hard to reach and they are all on a slight angle, so I don't know....

I wouldn't tighten that plug down just yet until you explore some options.

My kingdom for a garage so I can drop the engine right now.

I'm going to have the car towed to my friends house with a garage.

Drop the engine and try to use this tool so I don't have to remove the head. Hopefully the tool works as advertised.

http://www.back-tap.com/back%20tap%2...20section.jpeg

If it doesn't then I will remove the head and run a tap from the inside out from good thread through bad.

If all that fails then it's off to a local machinist.

Ok I just looked in Wayne's How to Rebuild and Modify and I see what is involved in removing the head: camshaft housings, chain, special tools, ugh.

I think I am about to get raped by my indie P-car dude.

Do you have the valve cover off? If not, remove it and see if you can get a better look at whats going on. I'm really hoping that you're just having trouble getting the right angle on the plug hole.

To prevent messing up the treads try starting the plugs with a piece of rubber hose slipped over the end of the plug. Once in, tighten with the tool. If not 100% right, the tubing will turn on the plug. This can get frustrating, but will prevent forcing the plug.

I could not find the thread, but someone either here or on rennlist had a bad spark plug hole, and they successfully used one of the internal thread chasers like you are showing. I believe it was the #5 or 6 plug hole that was cross threaded. He pulled the valve cover off and was just able to get the tool inside and repair the damage. I have looked on PP and RL for the thread or post about it, but I can't find it anywhere. Good luck!! Tony.

I have (on a bug) taken an old spark plug to the grinder. From the mid point to the end tapered off the threads evenly so that the beginning of the thread is barely visible.
With no force tried to bypass the damaged thread at the beginning of the spark plug hole engaging hopefully good thread further in. Once engaged it may straighten out your problem without too much trouble.
Mind you it was somewhat easier to see the alignment in the hole.
When the plug was "cock" threaded, were you using any force or just rubber hose or socket and extension?

I was using the Porsche spark plug tool. I turned it with my fingers until it stopped, then I used the Porsche allen key for a 1/2 turn. That's when I realized it wasn't getting any tighter with the key and the tool was protruding too far from the hole.

I'm kinda with Bill on this one... it's pretty damn hard to crossthread a spark plug by hand, you'd have to cranking down hard with both hands. That's why whenever I do spark plugs I never start with the ratchet. I don't use the porsche tool, I use an extension and spark plug socket or some combination thereof depending on the car. Still, it's nigh impossible to cross thread them by hand. If you were just using your fingers... maybe it's not cross threaded. You might want to try some anti-seize. Yes, I'm one the people who believe in anti-seize on spark plugs, but only on the base threads, and of a conductive type.

How hard have you tried to move the plug beyond where it feels like it doesn't want to turn more? What did the old plugs threads look like? If they hadn't been removed in a while, there could be corrosion, etc...

I agree - I don't think you have cross-treaded the plug.

NO,NO,NO!!!!

Pull the engine and get a straight shot at it. My brother is a machinist at the Jet Propulsion Lab in Pasadena and I did the same thing and he said "Do you want to eff it up or do you want me to fix it". Don't just think you can ram a plug chasing tool into it! It takes a LOT of finess and expertise to not eff it up. Get a really, really experienced person to chase the threads. If you pull the engine take it to someone whose done this many times before. The difference is a $50-$100 shop charge vs. you effing it up and its a few thou. $$$ after you eff it up. Take that as gospel. I CAN'T EMPHASIS THIS ENOUGH, DON'T TRY AND DO THIS YOURSELF!!! IT SEEMS EASY, BUT YOU ONLY GET ONE SHOT AT NOT PULLING YOUR HEAD. THE FINESSE OF DOING THIS RIGHT IS WELL WORTH THE BUCKS TO SOMEONE WHO REALLY, REALLY KNOWS HOW TO DO THIS!!!!

With the difficulty in access to the work area and the expense of fixing this once screwed up,
I think taking it to a pro isn't a bad idea...
I would have to agree with Hugh on that point!!
Perhaps at some time in the cars past someone had cross threaded that plug and you are running in on those mis cut threads.....
Hugh, detached member? Ouch!!!

Thread Back-Tap Tool
 

I finally found the threads about the tool you were asking about.
http://forums.pelicanparts.com/showthread.php?t=304134&highlight=stripped+sparkpl ug

http://tinyurl.com/55p2wb


There have been several successful repairs made with that tool. Hope this helps, Tony.SmileWavy

The search function was a PITA:mad: to be able to find the threads and postings that I needed, and I actually made some replies to the topic on some, and still it was difficult to locate.:confused:

http://forums.pelicanparts.com/uploa...1211759187.jpg

This is a picture of 1, 2, and 3 from May 25. these plugs were just installed back in October. I still have the plugs and the threads are fine. Maybe my car was mad for at me for switching to NGK vs Bosche.

Honest to God I was using the Porsche tool but I was turning with my left hand using fingertips as it's hard to reach back there.

When it encounters resistance, I can actually still turn it more but very slowly. It's not like the usual feeling where it basically stops and you know it's time for the ratchet.

I did have the plugs out for a week as I was waiting for the fuel injectors to come back. Maybe some debris (tree seed, twig, ?) is actually in the threads?

At this point I need to drop the engine and eyeball the hole.

Thank you!!!

I guess I would have to find out who is an expert in my area. Then load the engine on a pallet and rent a small moving truck with a electric lift gate.

NGK in a 911... say it isn't so... in a 912, I'd be okay...

Yeah, I'd pull it out and look at it. As Bill said, maybe somone else cross threaded it at some point, but I promise you that you didn't with your fingertips.

I can no longer find WR7DC anywhere locally.:(

I know that Hugh is being cautious and trying to save you from a major screw up, but as another opinion - I cross threaded a plug a couple of years ago and had good luck ( and maybe that's all it was) carefully chasing the threads and reinserting. If you were installing by hand I'll bet they aren't buggered too badly.

Well I ordered the Back-Tap tool and it should arrive this week. I will use it Saturday and post an update.

Why?

Good for you! I admire a man that has confidence.

I humbly disagree...spend the money and get the right tool as noted in the link to Grady's post. Dropping the motor would be one of the last resorts considering you have not applied any more torque other than with your fingertips and a 1/4 turn.
When using a tool as described in Grady's post, apply plenty of grease to the tools threads (cutting edges). This will catch any small bits of metal that may be removed with the tool.

I just ordered one from my local auto parts place. They
said they will match the $45 Amazon price, no shipping,
3.8% sales tax, should have it next week.

“KD Back-Tap 14mm Internal Spark Plug Rethread Tool.
Patented design allows for chasing spark plug threads
from inside the cylinder head and working outward.
This tool uses the better threads at the base of the
spark plug port and greatly reduces the chance of debris
falling into the cylinder. Works on 14mm spark plug
threads. Length of 6" allows for deep well plugs. Tool
can be used with 1/2" socket or wrench. Availability: In
stock Usually ships within 24 hours. Ships via UPS.”



They say it is 6" long.

Next week I’ll take some pictures using it on a disassembled
head and try it on a complete engine. One issue with a 911
is that it make the turn and fit down the sparkplug opening
and clear the chassis without removing the intake valve cover.

This looks like a tool that belongs in everyone’s tool box. I’m
going to see if it is suitable for regular sparkplug thread
maintenance. This has always been a difficult issue.
Perhaps it is somewhat solved.

Best,
Grady

I guess I'm being snobbish, I just think all 911s should run Bosch even the ones that came with Beru, but I ran NGKs in my 912, my WRX, etc... so it's not like I don't like the plugs, just don't think they suit 911s that well.

Problem solved--you won't believe it!
 

Ok here is the update I promised. I couldn't work on the car Saturday as I was in West Virginia most of the day. I got the Back-Tap tool and a mirror on a telescoping stick. I started working this morning.

I removed the valve cover and used the mirror to peer into the well. Boy was I surprised to see this...


http://forums.pelicanparts.com/uploa...1213580749.jpg
http://forums.pelicanparts.com/uploa...1213580773.jpg
http://forums.pelicanparts.com/uploa...1213580797.jpg
http://forums.pelicanparts.com/uploa...1213580822.jpg
http://forums.pelicanparts.com/uploa...1213580844.jpg

What are those white fluffy things? Why they are Bounty paper towels (the quicker picker upper).

http://forums.pelicanparts.com/uploa...1213580916.jpg

So I used my handy flexible claw to remove all traces of the paper. At this point I am elated--all this heartache caused by paper messing with the threads.

So I eagerly grab the plug, insert it in the plug socket, then start to turn and the same things happens again--two turns and then resistance.

At this point I know I will have to use the Back-Tap.


http://forums.pelicanparts.com/uploa...1213580630.jpg

http://forums.pelicanparts.com/uploa...1213580668.jpg

I lubricated the threads with grease and inserted into the chamber. The Back-Tap has a knob on top you turn clockwise to pull the draw bar and adjust the tapered thread to full 14mm.

Now this is easier said then done as the tool is just too short. I say it needs another two inches to make it a perfect tool. I could just BARELY turn the draw bar knob with the tips of my fingers. Compounding the problem is the the body of the tool wants to turn with the knob.

So I pushed down on the tool so it rested against the piston then I turned. The friction from the piston held the draw bar and let the knob turn. I then grabbed the tool and lightly tried to pull it out. The draw bar had not expanded enough so the threaded tip slipped easily past the threads the tool came out. I put it back in and turned the knob some more.

Again I tried to remove the tool and felt the thread finally engage. You have to be careful when turn trying to back tap as it's easy to turn the draw bar knob, thus releasing the draw bar and the tool slips out.

The instructions say you should use it 2-3 times expanding the diameter each time. I did it a total of four times. I did feel slight resistance but nothing I would classify as "torn up threads". I also did not see any metal particles in the grease. Regardless I did clean the tool and reapply new grease each time.

I grabbed the plug again and said, "here goes nothing". Lo and behold the plug went in like butter.

I started the car and she ran just fine.

So the tool is worth every penny of it's $50. The only con I have is that it just needs to be longer--about two inches.

Thank you every one here for your support.

Congrats Howard, glad it worked out, and I knew the threads couldn't be too bad.

That's a pretty damned clever tool.

Sounds to me like you had miniscule amounts of debris or corrosion. You can tell just by looking at the plug that it's not cross-threaded. Personally, i would've just twisted a bit harder inserting it the first time.

congrats and well done, you should be proud of yourself. a lot of people wouldn't have stuck it out. Not sure what those white things were, I thought maybe electrode at first.

Nice job, I am glad it worked out!!
Paper towel gave it enough of a push to start the plug down the wrong path?
Looks like an interesting tool.

Great post!

hell'ova wild adventure tale

Ok, fess up, where did the paper towel come from?

Neat tool...bookmarking this thread.

How the $)(@# did you get paper towels down in there? :eek:

http://forums.pelicanparts.com/suppo...s/beerchug.gif

Nice!