uberhahn

*** Update***
Over the past 48 hours I've been able to fix and drive the 4Runner with the stripped hole. I will post pictures of the tools and procedures used shortly, but in the mean time, a few lessons learned:

I was very afraid of cutting into the head with a tap. But, I figured either I spend $25 in tools and try to do it myself, and if I screw up, I'd have to pay $500 for head work anyway.

I purchased the Sav-A-Thread sparkplug kit from Murray's Discount Auto. It is manafactured by Heli-Coil and does not use a spring type adapter. Rather it uses a solid one that is held in place by small "teeth" (pics to follow). This kit is ment to be used without a socket (attaches directly to a 1/2" ratchet extension). I like this a lot more than the AutoZone version that fits into a 7/8 socket. It was a lot more stable, and allowed me to remove the tap without other tools. Again, pics will follow.

The whole tapping process took roughly 2 hours. Probably could have been quicker, but I went slowly. I greased the tap heavily and only went about 2 revolutions deep before removing, cleaning (with brake cleaner), and regreasing. I captured a LOT of aluminum this way in the sticky grease. Once fully tapped, I used a skinny funnel and poured some oil into the combustion chamber directly. WHY? I used my shop-vac with a 1/2" OD flexible hose to vacuum out any debris (and there was a lot). I did this multiple times (4 to be exact). I figured that the shopvac would suction better with a fluid. I had some frustration in that the hose came from a coil, therefore it wanted to stay curved. I had to let it sit in the sun for 10min or so in order to make it straight.

Installing the adapter was easy, as the threads were clean. I used anti-sieze on the sparkplug, threaded the adapter on the plug, then RTV on the adapter. It took a few tries before the adapter stayed in the hole. The first few times, it backed out with the sparkplug. I used copper RTV (rated for 700 deg F). I debated on the merits of using LocTite, but in the case I screwed up, RTV would be non-permanent.

To seat the adapter, a punch like device is used (included with the kit). It seats just inside the adapter (1st 2 threads). It is chamfered, so that when it is struck with a hammer ( I used a heavy plastic one), it expands the adapter, essentially wedging it into the head.

I let the whole thing sit for 24 hours. Picked it up today. 200miles with no problem.

Next steps: check all plugs and replace with Denso. Also, I will take off the ACDelco coil I got at AutoZone and keep it as a spare.

Overall lessons:
- must keep a fire-extinguisher in the vehicle. When the sparkplug blew off, the only thing keeping the engine compartment from flames was the fact that the coil pack was over the hole. I only would have lasted for a few more minutes, as it is now only a blob of molten plastic.
- the Save-A-Thread kit was top-notch, and I like it more than the AutoZone brand, due to the socket requirement.
- when tapping, I used a rag to support the ratchet extension. Why? I could still turn the ratchet, and it helped me keep the whole thing straight.

Look for a full write up soon with pics.

uberhahn




:pat: I was driving today, and heard a clicking noise, then what sounded like an air leak (loss of compression). Temperature never moved.

The passanger front ignition coil was melted. The spark-plug was loose and the two electrodes (bosch 2) were melted as well.

I got a new coil and sparkplug, but can't put the plug back in the hole...

Is it possible for the threads to have stripped somehow? The new plug turns and turns, but never bites. I'm trying to figure out if the hole is enlarged and of the threads are there. Is there an insert in the head for the threads, or is the head threaded itself?

Is there something I can do without taking the head off? How to check if the threads are stripped?

Any suggestions are welcome, urgently.

uberhahn

I purchased a repair kit. It consists of a solid insert, versus a spring coil type, though both are available. The instructions say to use hight temp RTV.
Question: RTV or Red Loc-Tite? RTV is 700deg resistant. Loc-Tite is 350, but seems more solid in it's application.
Again, opinions welcome.

rimpainter.com

Well, first of all, you (we) need to figure out what caused the ignition coil to melt. I mean, let's just say you get a new plug back in there; who's to say it doesn't happen again?

It sounds to me like someone stripped the original (Bosch +2) going in, and it worked itself loose. Who put that plug in? If it was a reputable shop, and you have receipts and a good case, they may be liable.

If you installed it and the threads are truly stripped, you could tap it and helicoil it I suppose. I have done this on a couple things before (other cars) and it worked just fine for a stripped exhaust stud hole in the head on a Nissan Maxima. The thing that worries me about this here is the shavings going on to the piston. They should melt, but that would really suck if they scored the sleeve somehow.

One step at a time though. First, identify if the threads are stripped (plumbing camera?). Then, figure out what caused this to happen. Also, I am not sure if Bosch +2's are ok for this engine. You might want to check that out also. I might be wrong on that though.

marko3xl3

You are right.

Brainfood: http://au.geocities.com/ozbrick850/e...boschplat.html

uberhahn

Sadly, I don't know who installed the plugs. Ironically, I have new Denso's waiting in my garage...

I have no experience with the Helicoil. However, that's probably the cheapest solution. I think the plug has been stripped for some time. I've only driven this vehicle for 4K miles.

Still, does anyone know if the threaded section is an insert, or is it actually a part of the head?

uberhahn

manofsteele2003

Didn't you buy that truck off ebay?

uberhahn

Actually, the truck never sold on ebay. I contacted the dealer about a month after the auction was over. Still had it. Flew out, drove 750 miles back.

uberhahn

Found the same symptomps discussed here last year...love that search button.

I'll get a quote on head removal, but in the meantime, I'll search for the right helicoil...

Previously Discussed

reggie 00

For what its worth.

I had the same problem in a honda (aluminum head) a while back.
I helicoiled the bad hole and installed the plug. Make sure you get it in the same orientation. I used a little gease to keep the shavings down. Ran that car for 4 years before wife seized the motor after the coolant pump went out.

hope it helps and good luck.

Elton

any thing bosch or fram is junk

MTL_4runner

That's the right thread for you (not sure why back then I was leaning so much toward having the guy put in a used engine?!). I'd definately pull the head to do the helicoil but beyond that, a headgasket and a new coil pack you should be back in business.

Ringmaster

Whenever I change plugs, especially with aluminum heads, I always coat the threads of the new plugs with anti-seize before putting them in.

Many cylinder heads by all manufacture'rs [sp] have been ruined by the threads galling while removing spark plugs.

Just my 2 cents worth....

uberhahn

bump for the update

khaug

Sounds like you did a meticulous job! I suggest you tighten the plug (and check all the others) with a torque wrench.

My guess is that combustion gasses leaked past the loose plug and melted the coil. I can't imagine this happening any other way. If it had been an electrical problem, a fuse would surely have opened before passing enough current to melt a coil!

Now, the next chance you get to look in the engine compartment of a mid-'80s Porsche 911, imagine doing the helicoil repair on it with the engine still in the car! A friend of mine did this while the car sat in the paddock of the road racing circuit he was at. This was some years ago, and the repair is still holding just fine.

Good luck.

uberhahn

Actually, the plug was all the way out of it's threads. When I removed it, there was no turning required. I simply applied a magnet to it to remove it. I think it was being held in only one revolution of thread. There was still aluminum on the sparkplug thread.

This weekend's activities will include a full ignition overhaul (new Denso coils, new plug wires for the other side, along with new wires). I will use the current setup to run a few Seafoam treatments first, change oil, blah, blah... Should be smooth.


Uber

mt_goat

Good work, glad you fixed it. Has anyone figured out what is causing all the thread failures on these heads?

Potomacduck

Just curious; when you were tapping the spark plug hole, how did you prevent any of the tiny metal shavings from falling through the sparkplug hole and into the combustion chamber?

mt_goat

See post #1

surf4runner

nice fix!

Bosch +2 have been in my 4runner for over 25K miles (learned they were not a good idea after the fact) w/o ANY issues. get good mileage and perfomance.
i have not seen any of these issues mentioned in the write-up. BUT i will replace them w/ NGK when its time
i have also used them in the 22re for over 150k mi.

uberhahn

Yah. I doubt that this is a spark plug issue directly. The PO was a POS and didn't use a torque wrench. There are other engines, though (like some Mercedes) that have a particular sparkplug in mind. Though there are others available that fit, the thread pattern may be just different. In any case, I don't think that's the issue.

Through my searches, Cyl 1 (Front Pass) seems to be the one most people have had issues with. Hmmm....

GrizzlyNC

I COMPLETELY agree!! I had put Bosch Platinum's in my 22RE and they only lasted ONE year.. And there were MAYBE 13K miles put on them before the engine started to randomly sputter while driving. I checked around a few places to see what they thought the issue was and one guy look at the truck.. looked at me and said.. Did you put Bosch's in that thing? I answered yes.. he shook his head and said "Why would you put a European plug in an Asian vehicle?" I replied with well I figured since they MAKE them for this application they would be fine... He insisted I go pick up NGK or Denso plugs and my sputtering issue would go away.. Sure enough!!! I put in NGK and have had VERY good results .. and as for Fram.. Just look at the test's done on them..