glenncof

I was replacing spark plugs in my 1985 911 and one of the Bosch plugs broke.

It broke at the mid point of the body between the nut portion and the barrel portion just above the threads. It is surprising, very thin (!) at this area and it appears this may have been cracked.

I plan to go to Sears to get some extraction bits and I am wondering what size.

Does anyone have any expereince/recommendations ?

Thanks

Glenn

Peter Zimmermann

Glenn: I must admit that I've never seen your problem, but if I did I would take a plug the same as what is in your engine and break it (by securing it in a vise) in the same place as the one in the engine. The next step is to look at what you've got to work with and plan from there.
Pete

glenncof

Ok, I got it done with "easy out" extractor bits from Kragen ($12).

Here is the picture of the broken plug and easy out bit.

There does appear to be rust on both pieces at a crack boundry about 2/3rds around. I can see the fresh metal that sheered.

jimq

I have never seen that happen before! Strange. Glad it came out so easy

theiceman

I just gotta ask . How on earth did you manage to get the easy out way down the hole and grab and remove so effectively?

glenncof

I used a 3" extension with a socket which mated to the #10 easy-out. I wrapped this with duct tape to hold it together. This assembly was about the same length as the Porsche socket tool.

As you can see in photo the thread portion of the plug is tapered which worked very well (read as large mating surface) with the easy out taper. I suspected something like this judging from the top portiopn that came out although I did not expect a smooth taper which is best.

Other than this, the job went easier than expected since I removed the air condition pump and heater duct. It looks really (scary) tight but the Porsch plug tool had a rubber insert to hold the plug and a 10mm hex head at the top. I used a 10mm hex-head socket going into the porsche tool. Intially I used a 3/8" breaker bar then a racket for removal. Installation was the rachet and final tightening with a 10mm allen wrench (porsche tool kit.). I used my 'caliberated' hands to get 22 ft-lbs..or whatever it is supposed to be.

I'm always worried when I have not change the plugs myself previuosly, of the possibility of bad threads, and cracking the ceramic with off-axis torque.

theiceman

Great Job !!

hartzpainting

Well I just had to write my experience with the same scenario. I
broke a plug, it was flush to the head with crumbling ceramic staring at me, threatening to find its way to the cylinder...I had the shopvac running as I carefully chipped it hollow, and miraculously was left with the nicely hollow seated post. I then inserted my screw extractor bit, attached to a 5/8 socket, placed it inside the hollowed out plug, used a breaker bar and gave it some muscle...and heard a loosening pop...it turned out like butter after that initial corrosion broke. Im so grateful...no head removal, no shop cost. Just $8 at Ace, and a lofts prayer. Just had to share. 94 Ranger, V6...no Porsche here...but sports gratitude.

Steve Weiner-Rennsport Systems

Well done gentlemen,.....

I would only caution someone faced with the same problem to blow out the plug well very thoroughly with compressed air before beginning the process. This ensures that no bits of ceramic can accidently fall into the open hole when the plug is finally extracted as that would ruin your day.

IXLR8

I'd take it a step further. I'd insert the tip of a tapered wooden dowel into the opening of the barrel (the remaining portion of the spark plug in the head) so that nothing can be blasted into the cylinder while doing so.

The removed upper portion of the spark plug will confirm that no chips or pieces of the ceramic have gone missing.

User 4221

Steve, would rotating the crank to TDC on that cylinder help? This would ensure the valves are closed and can be vacuumed/blown out afterward.

IXLR8

Possibly a defective spark plug or it may have been over-torqued when it was installed. It pays to use a torque wrench, even when the user is experienced and has a zero chance of stripping threads.

theiceman

Steve is suggesting you blow it out with air BEFORE starting the process .. so you get all the bits of ceramic out before you start with your easy out. The remainder of the plug blockes the hole. After removing the last peice of the plug DO NOT blow any air in their before fitting your new plug in. Once the new plug is in and seated go to towm if you feel it necesary.

Steve Weiner-Rennsport Systems

Not much really; if a piece if the ceramic falls into the cylinder, one would need to extract that before starting and its simply good practice to be proactive about that beforehand.

IXLR8

You normally do that with any spark plug, especially those sitting in a deep well as we see so often in cars. I'd even loosen the plug a turn or two to dislodge the powdery aluminum oxide that forms. In fact, you can even flush the well out as they have a drain hole out the side of the head in most cases. I'd then blow it out with compressed air and then remove the plug.

But I hear what you're saying above. I remember blowing out the area out when I once broke the upper ceramic portion of the spark plug...easily done if you've worked with tapper seat spark plugs...they can be a itch-with-a-B to remove.