ether_joe

Okay. So I had a problem this afternoon which may have grown into a bigger one.

#1. I'm driving along the highway at about 80 in 6th, when I start getting a loud puttering from the engine. I pull over and see that my #4 cylinder sparkplug wire has come out and is just sitting on the top of the engine. At the end of the wire, lo and behold, is the sparkplug itself.

#2. I notice that the hook tip of the sparkplug has broken off.

#3. I call a Porsche mechanic friend and discuss. I then replace the sparkplug with the handy sparkplug tool from the Porsche toolkit.

#4. I tighten the sparkplug down with what I think is enough torque, but not too much or so I think

#5. I start the car back up, and drive to the nearest Kragen on 3 cylinders, and buy another sparkplug. I go to my friend's and we take out the old plug and start putting the new one in.

#6. Here's where the story goes bad. We take a torque wrench and begin torquing to spec. The sparkplug starts to screw down, meets resistance. . . and then the resistance eases and the sparkplug starts turning again.

And that's where we stand right now. I can't tighten down the sparkplug. So. . . goddammit. . . have I stripped my sparkplug thread? Did I tighten down too hard at step #4? Could the original problem which caused the sparkplug to pop out, damaged the threads in the process?

I changed my sparkplugs last spring.

Potential solutions. We did some digging around on Rennlist. . . seems like a heliocore solution wouldn't be advisable for a high-compression situation like a sparkplug. We are considering the possibility of bringing the head to a machine shop and having them re-thread the hole. Or, another potential solution, we could drill new threads and use a bigger sparkplug?

Anyhow there you have it. suggestions and feedback are appreciated.

Mike C.

A friend of mine successfully used a Time-sert on his BMW six. I don't think there is any problem so long as you get the right insert and follow the directions.

triscadek

Step 4 may have stripped the threads. What did you torque it to?

Once I feel resistance, I just snug plugs maybe another 1/2 turn or so... just enough to crush the washer. I've never torqued a plug.

The good news is that you can tap it out and use a helicoil for a spark plug.

My nutcase ex brother in law rode my motorcycle with the enricher on and fouled the plugs. When he was attempting to clean them or whatever he was doing he crossthreaded one of the plugs and ruined the threads.

I took the bike to a buddy that ran a NAPA service center and I trusted to be competent.
He tapped out the threads with a generous amount of grease to catch the metal shavings to keep them from getting into the cylinder, cleaned it up and glued in a heli coil.

That was in about 1995 on a Kawasaki Z1 R 1000 with a brand new Wiseco 1075 kit with 12.5:1. compression. I put another 15,000 miles on that bike, dragged it quite a bit and generally ran the hell out of it.

I sold that bike to a buddy and he's still riding it with that heli coil in the #4 hole. That bike had an aluminum head also.

ether_joe

thanks guys for the info. Yeah, I torqued the plug. . .this was on teh side of the highway with the porsche sparkplug tool so no torque wrench. Past the 22 lb-ft though I expect.

well time-sert has a whole section for sparkplugs which makes me feel a lot better. I gotta measure the plug (anybody know the size?)

FRporscheman

Do you think it would be a problem to tap and helicoil (or timesert) the spark plug hole on a 16v engine? The plug threads are all the way in there, deep in those wells.

Jay W

Its hard to say how badly the threads were messed up causing the spark plug to fall out in the first place. I imagine as the spark plug was backing itself out, it was eating the threads in the head as it wobbled around with each compression stroke.

Then if you were on the side of the road and didnt allow time for the head to cool down before tightening the plug in, the heated up aluminum threads were soft, making it easier to strip them out. How long did you let the engine cool down? I know you were on the side of the road and needed to make a repair but I generally never change plugs on a warm engine for fear of stripping the threads in the head.

TRWright

*ding ding ding*

FRporscheman

From the time he called me to the time I got there, tried a magnet to fish out the electrode that broke off, to the time he decided to put the broken plug back in, it was at least 1.5 hours.

OK so a vaseline-soaked rag, a greasy spark-plug tap, a thread insert, and that's it? Almost sounds easy...

luckett

The only option now is to take the head off since there are likely all sorts of metal particulates in the cylinder...

FRporscheman

We taped a tube to a shopvac and sucked some debris out, then we used compressed air to agitate the debris left over, then we used the vacuum again, and repeated once more. Then Sean drove the car home (1.5-2 miles away) with an open spark plug hole. Don't worry, we disconnected the #4 injector, and removed the #4 ignition wire. Man, that car sounded like a disgruntled Harley bike.

But anyway he drove it so if there was anything left in the cylinder, it has already had its way with the cylinder walls.

Imo000

As suggested, first try the helicoil insert then if that doesn't work remove the head.

I've used a helicoil on a friend's car (same thing happend to him as it did to you) and it has been trouble free for the last 2+ years.

FRporscheman

At first I was skeptical about helicoil, since I've heard it isn't the strongest thing in the world, and a spark plug thread holds a lot of pressure. But once I realized timeserts are steel and helicoils aren't (what are they, aluminum?), I realized that helicoil would be a much better route.

ether_joe took his car to the mechanic my dad used to use, and he's gonna helicoil it.

inactiveuser92616

helicoils are almost always stainless steel. They are designed to work in aluminum just fine, read and follow their instructions.

swimmingly

Joe,
Does the new spark plug go all the way in or does it meet resistance and stop halfway?

Some time ago I stripped the first few threads of my spark plug hole. I bought a tool called the backtap and used the good threads on the inside to cut at and straighten out the top threads. If this sounds like it'll work for you, let me know.

Yummybud924

I don't know helicoils don't look strong but if you do it properly I think they are actually pretty strong maybe even stronger than the original aluminum threads. you won't strop the helicoil anymore and I think they work pretty good.

most of my water pump botl holes were stripped and I helicoiled them all and it worked perfectly.

I'd prersonally take the head off I don't think it's possilbe to get all the metal out of the cylinders .


maybe attach a tube to a powerful vacuum somehow and stick it in the spark plug holes to get as much out as possible.


mover the piston up as far as it will go up and then you also stick a long greased qtip taped to a pen or something to extend it and then fish around into the spark plug holes to get as much of the metal out.

if you have a tiny bit of small metal bits left in there they should blow out of the exhaust when you run it..