Spark plug repair kit tap will not grip existing threads in spark plug hole

Question

I have a 2005 Hyundai Elantra that recently blew out a spark plug. My understanding is that I need to re-tap the spark plug hole and insert a sleeve. I purchased the Lisle 65200 plug hole repair kit for the job.

The tap starts with original size threads, then has a taper for a short distance, followed by a wider size of threads to fit the sleeve.

Problem: The original threads are too stripped out to drive the tap downwards to the wider part. Because of this, I cannot get the threads to bite into the metal to begin tapping out the hole.The tap just spins at the tapered part (I can verify this by the pattern of the grease in the flutes of the tap). I need to get it deeper to start biting into the sleeve size threads.

I would greatly appreciate any advice someone might have in this. Thank you for your time.

Answer 1

Are you sure the piston isn't in the road? If it was at TDC, it could be keeping the tap from biting into the metal.

If that fails, you might need to try a little more of a drastic measure. That'd be to rap on the end of the tap using a hammer to get it started. If you try this route, you don't want to hit it hard, just hard enough. Tap on the end, then turn the tap a few degrees, then tap it again with the hammer ... keep doing this until you can start to feel it bite. You don't want to do this with the piston at TDC, because you could cause it damage. The method I describe will be nerve wracking.

Also, glad to hear you're using grease in the flutes of the tap. Make sure you are taking the tap out very often to clean and regrease. It'd be really easy to get the metal shavings down into the engine if you don't.

Answer 2

I have not used this system but from what I can see on their web site, it relies on the lower threads to engage and then pull the rest of the tool down into the material.

If there is not enough "meat" in the hole to allow the lower threads to bite, then I don't see how this can be used.

My advice at this point is to pull the head and take it to a machine shop and let them do it. Alternatively, get a replacement cylinder head from a local salvage yard.

Answer 3

I just did this on a 2005 Grand Voyager, and had the same problem.

Using the OEMTOOLS 14mm Spark Plug Rethreader Kit from Autozone, I just kept applying as much pressure as I could until the tap finally grabbed and started cutting the new thread.

Answer 4

spark plug threads are not the same as metric or ase threads or pipe. they are a unique taper. A quality parts store will likely have access to the hole chaser tap you need so long as you take your plug along to ensure you get the right one. A good one will have a seat surfacer as part of it that either cleans the bevel for a wedge type plug seat or a gasket seat (metal seal ring) They do make a Helicoil repair for spark plug holes but I don't advise even thinking of doing this with the head on the engine as stuff WILL drop into the cylinder hole and damage your engine badly.

Answer 5

In the end, hammering the tap and turning it did not work to produce a viable hole that would allow the tap to bite. I spent literally hours doing this.

The spark plug hole is 14mm. But the threaded hole for the helicoil would be 18mm.

The well shaft leading the the spark plug hole on the Hyundai is about 6-7" deep and just under 1 inch wide.

The Drill Bit:

I did an online search for a chart that listed hole sizes for various sizes of taps. For the 18mm insert, a traditional tap would require a 16mm (0.63 inches) hole. Since the main part of the Lisle tool is 16mm, I purchased a long 16mm metal drilling bit.

The bushing:

Given that hole was 0.37 inches wider than the drill bit, it required me to fabricate or find a bushing to keep the drill bit from going at an angle. To do this, I took a one inch section of metal pipe, slit it down the long way, and compressed it in a vice until it overlapped in the slit. Then I wrapped tape around it until it could slide into the spark plug whole without wiggling.

Preparing the drill bit:

The flutes of the drillbit were well greased in preparation for the procedure. This will produce a lot of shavings. Better to trap them in grease.

How to drill with a drill bit that big:

The drill bit is bigger than most chucks will accommodate. The bit I purchased also was a smooth circle at the top instead of a step down shank or a shank with flat sides. I did not have a chuck large enough, so I used a hammer to get the the drill bit to bite. Then I used a pipe wrench (very important you put a bushing in the hole before doing this) to turn the drill bit. After a while, I bored out the entire hole.

Be careful doing this. At the end of the procedure the drill bit will want to fall into the cylinder. Be prepared for that and have an extra set of hands be ready to grab the bit before it does so.

The success!

After boring out the hole. I was able to use the Lisle tool like a normal 18mm tap without any issue. I simply hammered it a couple taps to get it started, then threaded the hole (making sure to back up and go forward throughout the process to prevent binding).