My Cylinder#1 spark plug hole is now stripped - How would you fix/address this? (more)

[Mark P]

I'll try to keep this story brief and to the point...

Prior to Saturday:
Car runs great, no issues at all

Saturday:
At 4PM, I load up the "trunk" with 4 snow tires and 4 wheels, and head to the tire shop to get them mounted (for the Golf). Temps in the 40's, I'd guess.


Discovery:
I'm naturally driving carefully so the tires and rims don't bang around and also as the engine is cold. I'm just cruising along on the highway. I then go about 10-20% throttle in 6th gear and hear what sounds like something dragging under the car. I immediately let off and it goes away. I slowly get on the throttle lightly again and there is the noise again. It sounds repetitive, similar to a flat tire, but only when on the throttle. I toss it in neutral and get off the next exit and roll into an adjacent parking lot as I shut it down. I pop the hood and don't see anything visually wrong. No fluids leaking under the car, etc. I start the car and hear a fluttering/flapping noise which appears to be coming from the passenger side. I shut it down again, for good. After pulling apart some stuff with the tools I had, I find the Cyl#1 coilpack gasket is hanging loose out of place. I remove that coilpack to find that the extension thingy (to the plug) is shattered apart and the plug is at a slight angle. I remove all of the shattered black plastic, and then finally remove the plug. I notice the electrode on the plug is slightly bent from where it should be. I attempt to replace it with another plug but I can't get it to thread on. I open up Cyl#2, compare the two, and can obviously see that Cyl#1 hole is bigger. As I place each in, I can not notice the difference and feel that Cyl#1 plug is just pushing down all the way - I can feel it jump across each remaining hump of a thread as it goes. The old plug did not have any full threads on it, but did have an aluminum colored dust on it. The car was then towed home. AAA Plus was added to my Christmast list (kinda makes sense with two cars in the 140k mileage range & with my commute, huh?).

So now my passenger head has a stripped out spark plug hole in Cylinder #1.


What Caused it?:
Not sure. I don't know for sure that nothing is wrong within the combustion chamber. I should probably do my due diligence to find out first - if only I had a medical scope.

I then recalled that I previously had a spark plug come loose once before. I had thought it was a coilpack going bad, but it was just a loose plug. Searching, I find my old post:
http://forums.audiworld.com/s4/msgs/1767143.phtml
I tightened it at that time (14 months ago) and haven't touched it since with no issues, until now.

As such, I am guessing that my problems are due to weakened threads, possibly due to once being overtorqued, but I'm not positive.


How to fix?
Replace the head - I have a replacement head lined up that I could use (thanks Jim!). What I don't know is how easy it is going to be to replace. I have fround the following references so far:

http://forums.audiworld.com/s4/msgs/1700892.phtml:
- Bentley says to pull engine
- dscottjr says engine pull not needed

http://forums.audiworld.com/s4/msgs/1700945.phtml:
- Head bolt tool needed

Insert Helicoil after removing head - Has been suggested if replacent head was not available. Can still evaluate combustion chamber and ensure helicoil does not go too deep.

Insert Helicoil without removing head - Doing it while the car is still together saves a ton of labor, but could result in shavings in the engine/turbo. Also the depth of the location of the threads may require special tools/jig to get in there while being aligned.

http://forums.audiworld.com/s4/msgs/1701117.phtml:
- Jeff Doyle - boscoj did it with the head in the engine on a non-S4.

Tom@ECS also mentioned that he saw a new tool in a trade magazine or similar which allowed you to thread from below upwards. This might help with shavings and also allow the tool to grab any good threads at the bottom of the hole, to align itself.

Misc reference:
http://forums.audiworld.com/s4/msgs/1697840.phtml:
- Similar issue by stradjazz


Ok, so please discuss. What would you do? What do you suggest? What's the easiest way to remove the head and what is involved (assuming no lift available)? Etc, etc?

And here's a big "P.S." that should be noted: I have a new clutch disc on it's way to be installed. With that said, I wonder if it's just easiest to pull the engine and tranny and take care of both at the same time. For those that have pulled their own engine without a lift, do you have links to any writeups or care to give a high-level description of the steps required?

Here's a shot of the plug while there are still a few pieces of broken plastic in there:



And here are more:

Parts that still existed that I managed to extract. The ring/gasket was blown out and half dangling around the coilpack


Some of the missing plastic is melted here:


and here:


Close up of the hard plastic on the inside and the soft on the outside. Is it supposed to be soft, or is that a molecular change from the heat?


What a new one looks like for reference:


The bad guy:


Notice the electrode pressed in slightly:


Gee, which one do you think blasted it's way out of an aluminum head? and of course, notice the missing tip on the plug as well:

[lemieux@curbside]

so dscottjr is right about that .
i would personally replace that head .. i think.
if shavings go down in there you might damage/scratch the walls of the cyl ..
i am not sure what other options you would have.

[reefer_bob]

I'd really want to pull that head to inspect for any damage in the combustion chamber... If the hole is bigger and the ground strap is bent, there's metal somewhere. Hopefully it's still in the CC, and hasn't been exhausted to the turbo.

Since you started it, and heard the clatter, I would think it's still in there. Additionally, if parts have been ejected, this would give you an opportunity to inspect for any damage to the valve seats.

I've always been very leary of helicoiling spark plugs for many reasons... The constant thermal cycling bothers me. It's not a part that you would put together one time only (intake mani bolt, exhaust mani bolt, etc) rather it's a every XX,XXX mile kind of thing. Finally, failure can drop more crap into the CC.

If it were my car, I'd yank the engine, put on a new head, and install the new clutch. You could also throw in a new after run pump, and some phenolic spacers, and......

IMHO of course.

[FixedWing]

I don't think you have a lot to lose. Mess it up and you need to pull the head which is where you started. Lots of others have done this job with the head in place and I haven't heard many problems.

Basically you are tapping a new thread and inserting a helicoil then snapping off the end turn tab. Most of the bits will be really fine. The only substantial bit is the helicoil end tab and I believe they have ways to make sure you can hang on to it. Maybe do it with the cylinder in a position where both valves are closed and then use compressed air to blow out as many bits as possible? I've also heard of people using grease when tapping the thread and withdrawing and wiping the tap frequently to try to keep a many bits out of the cylinder as possible.

If you do need to remove the head then then head is not junk. You should be able to have the hole built up by a shop and then a new hole tapped with the correct thread. No reason to discard the head.

By the way, I've also found spark plugs loose with low-by. The only thing holding it in place was the coil pack. I suspect that yours shattering is what allowed it to come out. I can only think that detonation is to blame. I now think it is a good idea to check the tightness of the plugs regularly.

Stephen

[ModifiedA4]

i wouldnt have any problems heli-coil'ing it with the head on.

i have some adapters for my shop vac which include a small wand and bristled brush which could get in the cylinder and vac out any chips.

also i believe a trick is to fill the cylinder with shaving cream which will tend to catch the chips and vac that out.

that being said, if time/effort/skill was no object, i'd pull the head and heli-coil it off the engine.

[FixedWing]

Would work nicely if done at BDC and then then engine was turned to TDC (with valves closed) then the cream and everything would be forced out of the cylinder.

Stephen

[reefer_bob]

I *personally* still wouldn't do it...

but then again, when it comes to my car and engines, i'm super conservative.

but you can probably tell that by my previous post.

[DAP@EPL]

[FixedWing]

[ModifiedA4]

• the article is a byproduct of me fubar'ing a kombi valve, lol.