Blew a spark plug out - how driveable is it?
 

I was having grand day driving in the mountains of West Virginia when early this evening the engine spit out the #6 plug. Threads in the head are screwed - the plug will seem to thread in but it never bottoms out and you can then just pull it out. So I have two questions while I figure out a game plan for tomorrow:

1) is the head permanently fixable - TimeSert or something else - or is any fix u,timately temporary and I'll have to replace the head?

2) is the car driveable long distances? Obviously it's not getting spark to #6 and I unplugged the injector so it's not getting fuel. The cylinder is still getting lubricated. So the fundamentals seem there. The engine is obviously imbalanced but this doesn't seem like a big issue. Not sure if the absence of heat on #6 only is an issue. I drove the car about 25 miles to my destination for the evening, and I'm ok driving it 90 miles to Pittsburgh tomorrow. in a perfect world, I'd nurse it home the 500 miles to Chicago. Sure it's slow and loud as hell, but all I'm concerned about is damaging the engine.

It's either get it home (renting a truck and trailer is going to cost a fortune, so I doubt I'll do that) myself or leave it in Pittsburgh, have someone fix it there (I've got a place to store the ar as long as needed), fly home and fly back later to get it.

Thoughts?

Drive it? No way. Fixing a head is one thing. A new motor is another....

What is driving it as-is going to do to the motor? I'm not saying it won't do anything, because I'm not sure. I'm one of those types that likes to understand everything :)

Do an Internet search on plug saver

https://www.toolsid.com/heli-coil/heli-coil-save-a-thread-spark-plug-repair-kits-22564871.html?gclid=Cj0KCQjwrpLoBRD_ARIsAJd0BIUmbV rvJi5TUDvdhZIw53UED_FiT_lG1CVXRlVgAF87OSc30eg7JfAa AvV0EALw_wcB

Any halfway decent auto supply will have one. Get a tub of grease to catch the chips, follow the instructions.

https://axleaddict.com/auto-repair/Blow-out-Spark-Plug-Repair-Using-the-Save-A-Thread-Heli-Coil-Repair-Kit-Ford-Crown-Victoria

. . . been there . . . Columbus to Albany . . .
Free advice - Uhaul truck and trailer - do not leave your car . . . unless you have very trustworthy friends in Pittsburg . . .

Also, if a plug blew out - what about the others ? It might be time for more engine work/maintenance ?

Wish you the best,
Regards,

I drove a VW bug from the middle of Mexico to Denver on 3 cylinders once. The tip of a valve pulled off, the valve fell part way in, got smacked back and the stem bent, which kept the valve up high enough that it didn't hit. I pulled the rocker, finished the Carrera Panamericana race, and drove home from the border. I don't recall if I pulled the spark plug, but upon disassembly I didn't find any additional damage.

I once, at an autocross, miswired my SC's distributor. Running on 4 cylinders wasn't super fast, but it ran. These engines have enough power on five for sure.

Is it possible to tap (is that all that is required for a plug hole saver, or do you need to drill first?) this in the car? #6 is just about as inconvenient as #4. I am dubious.

I would think driving without a plug in a cylinder would cause problems with the mixture - you have a path through the intake runner to the air box, and the air which gets up into the box that way is going to lean the mixture quite a lot, like any other air leak in the intake on the cylinder side of the air measuring system over on the right side of the intake. But maybe not?

One option is paying for some professional assistance, or at least opinion.

Having a shop help with repairs, temporary or permanent, may be the best approach. Sewickley in Pittsburg is the closest I can think of offhand, and Duane Smith knows these cars: dsmith@sewickleycars.com. Steinel's, a bit SE of Cleveland, is a good Porsche shop also. Someone may know of a better, closer, place. I just know these guys from race officiating.

Like you, I'd like something more specific than "just don't drive it any more." That may be exactly the right advice, but some explanation of what and how further harm is going to occur would be helpful.

All I can think of offhand is maybe a lean mixture, and you could do something about that by seeing if you could remove the intake runner for #6 and blocking its connection to the air box. Though perhaps removing the #6 intake rocker would be easier and maybe better - there is a whole lot of stuff over by #5 and 6 to get in your way getting to that runner.

As long as the engine compartment isn't very dusty, maybe you'd not suck much dusty air into that cylinder?

The engine is going to be out of balance, but you can keep the revs down to help with that. A chance of twisting the crank would not be on my list of worries.

You say you disconnected the injector. Good move, for sure, but where is the continuous (CIS injection) fuel flowing to? Did you find a way of plugging the line from the fuel distributor?

But you really should check out the U-Haul option, so you have some idea of the relative costs of things. I have trouble imagining repairing that particular spark plug hole without dropping the engine.

Checking the other plugs sounds like a good idea, considering. I can think of two potential reasons for this one being spit out: One is that it wasn't tightened on installation, but that would allow you to screw it back in (with maybe just the top few head threads broken off)and you say it just spins. The other is that someone along the line cross threaded things. When you have the engine out (at least eventually), pulling all the plugs to check for thread integrity might be in order.

Are you a PCA member? From time to time Porsche owners caught in a pickle get ahold of someone from the local PCA region to see what help can be had. You never know - maybe someone with a trailer might take your car at least to a local shop.

Holy Smoke! That dude in the video must have torqued that plug and insert to 200 ft. lbs. with a 1/2" ratchet setup!

Walt, thanks for that detailed note.

I forgot to mention that the car is running on a Megasquirt for fuel and ignition (Ford EDIS), so no CIS.

The engine compartment is a ton les crowded than a stock one, but I can't imagine tapping and threading anything with the engine in the car unless you had, I dunno, nanobots. Or ninja skills. Access is a PITA even though you can at least see the VC.

And I am very fortunate that I do have someone that I would 100% trust leaving the car with. It would sit with the owners Triumph TR4, Ferrari 456, old Packard and I don't remember what else. For working on it, the people from there recommended Charlie Hsu (sp?) first if I'm patient and then a shop named I think German Motor Works or soemthing like that (don't have it written down)

I think it might be cheaper or easier to have a transporter take it home than to rent a U haul.

As for why the plug blew out, that's the mystery. This actually happened to me once before either last summer or the fall before. I was in New Glarus, WI that time and didn't have tools with me but was within a short walk of a farm supply place so I just walked down, bought a few tools and screwed the plug back in. Thought it was bizarre but didn't think much of it again. At the time I figured it was loose and unscrewed itself, which doesn't make a lot of sense in retrospect but then again I screwed it back in and there it sat for 5-10k more miles....until last week when I put new plugs in. Felt OK when I threaded it in but obviously the threads were damaged and 800 miles later, boom. It's possible the threads were damaged when the top,end was rebuilt by the PO in 2013.

I would think the damage would be in just the top couple threads
You’re not going to blow a plug out of a dozen threads.
Grind done the first couple threads on the spark plug so to lead you past the damaged threads
You should get the plug in and working.
Bruce

Otter,

Sent you a PM with my contact info.

Let me know if I can help.

Dave

Put the plug and tool back in. Fashion a metal strap between valve cover studs to fit over spark pug tool to hold it all together. Drive home and repair correctly.

maybe you can use a longer plug with added washers to get a few more threads of engagement. I think id just wedge or strap it in there somehow.

Yeah, maybe a socket and extension that is just proud of v/c surface would be easier to hold down.

I'd like to thank in particular Walt Fricke for helpful posts and Dave Kost for offering another place to leave the car if I needed it.

After an uneventful drive from Davis, WV back to Pittsburgh and booking myself a one-way on Southwest for Sunday evening in case I needed it, I ultimately decided to drive it home. Leaving the car would have enforced a return for Grand Prix weekend :) (which I'll likely do anyway) and freed up a garage space at home for 4-5 weeks to allow me to do some maintenance on my normal cars without kicking something out of the garage, but in the end I concluded the only risk of driving it home was FOD in the cylinder and that that risk was very low, below my threshold for accepting it.

There was no way anything was getting threaded in that plug hole - yes, all 12 threads are stripped. I may not be able to see it, but I can feel it. The drive home was merely loud. I kept the revs down but otherwise drove normally.

In a perfect world I dream of being able to TimeSert (or whatever) the plug hole without taking the head off, but I'm not willing to bet on the odds that cutting lube will hold all of the shavings from cutting new threads and keep them out of the cylinder. So it looks like once the engine is out, the head's coming off and I'll be asking new questions :)

David

you might be surprised how well a smartphone can fit down near the spark plug holes and the quality of the imaging with the flash on. Could you take a video to see the condition of the threads?

500 miles on 5 cylinders, must be a recent record of some kind. Curious how much oil got spat out on the covers after 500 miles ?

Crud getting into the cylinder with the open plug hole is a good point. Hopefully the oil cooler area was relatively clean.

Good idea - I hadn't thought of that. May not have done me much good at the time as I only had my iPhone 5S on me and the camera isn't that great and there wasn't a lot of light. But my work Samsung has an excellent camera - I'll try it tonight.

I had a look under the engine lid in Pittsburgh, and it looked normal then in terms of oil. I'll look again when I get home, but I'm betting nothing significant. And it is pretty clean in there.

There must be some ways of adding suspenders to well greased cutting tools when preparing the hole for an insert.

One way guys change valve springs on an intact motor is to shove a bunch of string down the plug hole, and then bring the top of that piston up until it presses the string stuff against the valve heads. Of course, you leave an end of the string out so you can get it back out.

If you have a hemostat, or a grabber, you could probably reliably get the in through the plug hole to retrieve it. My notion is that you could grease the string liberally, and extracting it might get any chips which got in back out.

Nobody is going purposely to put aluminum chips into a combustion chamber. But a few small ones seem unlikely to cause any serious harm. I once decided to attach carburetor air horns through the air filter base with slot head screws rather than the studs and nuts which were usual for the purpose. The screws backed on the track eventually, the horns moved, and some small steel screws got sucked into various combustion chambers. I could hear when it happened as my wife was taking the final few laps of a race.

Some of the screws were spit out the exhaust. Some were embedded in the head or a piston. All this cleaned up reasonably well (no valve damage)though hardly perfect internal cosmetics.

While drilling/threading you might be able to blow air in the intake so it would come out the plug hole while you worked. Having a bore scope for use when done would be useful - you could use it to see what might have gotten into the combustion chamber. The grease on such chips might allow you to use the scope to fetch them out.

And someone who has done this on an intact engine may read of your problem and have better practical advice.

I'm assuming pulling the engine so you don't have to work while a pretzel is in order here. If you can put the engine up on a stand, you can rotate it so the plug hole faces straight down. A bit more awkward working on it, but you'd have gravity on your side relative to chips.

We are often cautioned not to put anti-seize on the plug threads, sometimes by guys with darn good credentials. But I'm more afraid of damaging the threads in the heads than I am of the plug not having good electrical connectivity to the engine, so I have always used anti-seize on the plugs for my VW and Porsche air cooled, aluminum head, motors.

Otter74. I also blew the plug in #6 a handful of years ago a 100 miles from home. I was able to thread it back in and made it home. My neighbor had a scope and the threads were about shot. Time for a top end at 161K. #6 was time serted. That was about 35K miles ago.

I figured somehow I missed torqueing that plug snugly. You can bet I double check them pups now. Good luck on yours.

I was looking through old forum posts a little bit ago looking for any historical reports on this and found one or two from years ago where the owner had to rethread the spark plug hole and did it with the engine intact. It doesn't seem so outlandish to me now that I read about it being done, and see photos. I have an outlandish hope that the threads are somehow OK but I am really doubtful. carreradpt, a comment of yours may have been on one of those old threads. The first time this happeend to be I did exactly that. Since my engine was completely rebuilt about 20k ago and the top end was done probably 17-18k ago there is no need for other work on the engine, just this. Maybe if I'd have left it with Charlie Hsu he'd have been able to do it with minimal invasion if his judgment allowed it, but I made my choice and it's my job now :) At least I'll be able to take care of some minor ToD leaks with the engine out.

I had the same thing happen in my 740 bimmer, while I had let a family member drive it for a couple of weeks. I didn't blame them for what happened but was pretty angry over the fact that they didn't tell me about it and kept driving the car. This thing sounded like a tractor at idle!
I did some research and decided to try to repair the plug threads. I rented a time-cert tool set from aircooled.net and bought some time-certs from amazon. The repair took me a couple of hours and was pretty straight forward. I put some vaseline on the tap to keep the shavings from falling into the engine, as much as possible. The plug torqued down nicely and has held fast now for 25k miles. My other option was to pull and replace the head; pretty major effort and $-wise.
I don't see any reason this wouldn't work on a flat-6. The access to the plugs is a little more difficult but I would give it a try.

Cheers, jt

is there room to get your tap and insert tool down the spark plug hole without a partial drop to get below the frame rails?

That freaked me out as his arm started shaking! That and where are all the metal bits from the cutting tool? I guess it's an American car so just blow them by the valves? :eek:

Glad to hear it worked out on your 740. I've seen enough that I'm confident that it's OK to do on my car. And thanks for the aircooled.net mention - I didn't know about the tools you can rent from them.

Not sure, as I'd have to see how much space whatever tool needs. Off the top of my head, without actually being at the car, I'd say I have about 6" clearance straight out from the surface of the valve cover with the engine in the car. My bigger concern, rather than merely space, is how hard it is too see in there. Even with my clutter-free engine compartment it's a lot harder to get access and to make sure you've got things lined up correctly compared to when you can look straight into the hole.

Speaking of which, this is the best photo I got this morning with my phone:



http://forums.pelicanparts.com/uploa...1561069440.jpg

Hard to tell any deeper, but the first few sure look buggered.

I still have a time believing all threads are wiped.must have used the Hulk to install
A loose plug is only going to wipe the threads that can no longer hold the plug under compression
Bruce

Otter:
The picture, as posted, is backward. If you flip it horizontally, it will look like what your eye would see if you were a rubber pinhead and could get in there and look directly (or had it on an engine stand). #6 is right next to the top of the oil cooler, which you can see in the snap shot.

The cylinder head has two drillings through the fins. The lower one, which is a straight shot in, is where the head stud is, with its round 10mm stud barrel nut - the things you tried to retorque/test and some confusion arose.

The second drilling is right above it, and is for the spark plug. The spark plug is not a straight shot. It angles up and to the rear some - that's the angle you have to set your spark plug wrench when R&Ring a plug on the right bank (up and forward on the left bank). If you pull the #1 plug and look in there (where you can stick your head), you will see the layout.

So my guess is that you have a fine photo of a head stud barrel nut.

Just spitballin here, if you did a partial engine drop and pulled the oil cooler can you get at the plughole? On a turn of the century vw beetle i screwed up a valve trying to install a helicoil type spark plug insert, hit the valve with the tap because i neglected to put that cyl at TDC. use grease on the tap to keep the shavings from dropping into the cylinder.

It can be hard enough just to get the plug threaded back there normally w/o crazy gyrations and extensions and swivels, I can't imagine helicoiling the plug threads. That is crazy talk. Sounds like the car is safely home. Take your time and do it right.

the idea is to grease the tap and slowly cut the threads a little and pull the tap out and clean it and repeat until all the new threads are cut and then install the insert

but if you got home I'd just drop the motor and pull the head and install the insert

It's really easy and basically foolproof if you will use about an 8" straight section of rubber heater hose or vacuum line that will fit over the tip/cap and snuggly onto the ceramic insulator of your new spark plug. You can then thread them in by hand and pull the hose off once the plugs are initially seated. Use the socket-extension-ratchet only to take the old plugs out and snug up the new ones you install.

Walt, I noticed that the photo got posted upside down but I couldn't tell the difference between the head stud hole and the plug hole without looking at it directly :) I know it by feel, though - i go straight down the hole in the VC and angle it towards the back of the motor slightly.

I wish I had thought of that when I was working on it last week. I knew that once, but had totally forgotten it. The people in the SJ Wagoneer that stopped to offer help and follow me back to dinner suggested that (and produced some hose) and indeed it makes it easy-peasy.

Given the above re: grease and doing it safely in the car, and that taking the head off is going to be, I dunno, triple the work, I'm probably just going to drop the motor onto a furniture pallet and do it there.

How do I do a partial drop? That is, what do I remove and what do I not touch?

Not sure if it was mentioned here, but isn’t there a tool or kit that includes a contraption that extends into the head to capture shavings from the tap / thread chaser? I think I’ve seen threads on Pelican about it. That’s what I’d want to use for a job like this.

I drove a five-cylinder 911 for a bit. It's a little like driving a diesel Yugo.

The re-tapping of the thread can be accomplished. You will definitely need mirrors and a light with the periscope + the exact length extensions. Ironically I had a local buddy break the spark plug in his 3.2 as he was removing it. The electrode + threads were still in the head. An extractor plus the light plus the mirrors plus magnets got it out.

PM me if you need to.

Walt is right, the picture is of the cylinder head barrel nut. But never fear, the repair is going to be the same.

Dropping the engine is pretty straightforward and, with proper tools, can be done in less than an hour. That will give you the best access and at least you could see what you're tackling.

Whether you pull the engine or leave it in, you'll need a deep thread repair kit like this. (The earlier version of this one is the one that I've personally used in the shop)

https://www.amazon.com/Lisle-65200-14mm-Plug-Repair/dp/B00RGNJ78A

Or this one. (Looks like you'll need to source the taps and inserts somewhere else though. More $$$)

https://www.stomskiracing.com/products/911-spark-plug-hole-repair-kit

Be careful, go slow, use grease on the tap, and it's a doable job without teardown. I've done the repair a few times with the engine in the car, and it's tight, but can be done. You might not have the luxury of years of experience though. The cause was that the spark plug was not tightened properly when installed. Over the miles, it loosened up and allowed combustion pressure to escape passed the threads. At some point the flame front acted as a torch and melted the threads on the plug, allowing it to blow out of the hole.

Do NOT attempt to do this without the piston down in the cylinder. If you have access to an air compressor, you can attach a piece of steel tubing to the end of a blow gun and stuff that down the hole to blow out any remaining chips.

Dannobee, thanks for those product links. Dropping the engine does seem straightforward - I've done engine swaps on other cars - though if one says it can be done in under an hour with all the tools, I budget for at least two. Still, that's not a lot. I appreciate those product links - I think I'd be willing to spend ~$300 on tools to avoid a drop, especially because I can fix my triangle of death oil leak with the engine in the car (thanks, Megasquirt). Thabsks for the reminder to put the piston at BDC.

I tend to go the simpler, more predictable route when faced with these dilemmas. I have found myself committed to projects that stopped making sense long ago. Case in point, I was fixing a barn door a while back. Thought I could do while it was still hung. Like you I did not think I needed to take her down... Three hours later, I took her down and did it the easier, and BTW, more enjoyable way.

Have fun. Don’t struggle. You know what to do with the engine out.

Edit - and if you have not dropped a 911 engine yet... it’s time you lose your virginity!! You will know and appreciate your car so much more.

DIY? If you're confident of your skill set, go for it. If not, don't make it worse. Sublet the repair to a good tech. Find one first and get an estimate. My WAG, $200 labor, but that's just a guesstimate.

There are techniques to gather aluminum drill shavings. However, al shavings can be vacuumed from the combustion chamber; ferrous materials with a magnet. Stainless steel Helicoil repair threads have a tang that is broken off to finish the installation. Make sure you account for that. In addition, position the piston at TDC with valves closed. A boroscope borrowed from your FLAPS will come in handy to inspect the chamber for other debris/damage.

S

You do NOT want to put the piston at TDC. The tap will bore right into the top of the piston. Turn the crank until the piston drops down in the bore. Removing the chips from the cylinder is easier by using the small pipe down the hole and blowing them out than by vacuuming them out. Vacuum simply doesn't work. Like I said, I've done a few of these. BTDT. The tool that I referenced comes with inserts that stay in place by deforming the last thread with a special tip that's included in the kit, along with using red loctite. There are no tangs to lose into the cylinder like with helicoils.