Need to rethread a plug hole from a blown plug
Feb 12, 2019 | 01:58 AM
#1
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Trailblazer
Joined: Jun 2015
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Need to rethread a plug hole from a blown plug
Bought an '11 Vic with the 4.6L back in June and a few months back I tried to change out the plugs. All came out ok except for cyl 4 which only cranked out 1/4 turn. Had a shop take it out and they said they had to redo the threads. I've seen videos where you can remove a stuck plug by drilling into it somehow, but because this was in the 4 position and hard to get to I'm guessing they just power cranked it out. Not sure but I'm guessing those threads are compromised now.
Well, this past weekend that same plug blew out of cyl 4. Inspection reveals a coil and boot jammed up underneath the fuel rail and a plug that I fished out without any turning. When I go to install a new plug it just sits on top of the threads and turns without going in. So I guess what's happened is that the plug rotated most of the way out but when it got to the last couple threads the compression blew it out the rest of the way, and that it's just the top few threads in the hole that are damaged. Inspection of the plug reveals that most of the threads are intact except for the 2-3 that are closest to the element.
So my question is...should I try to fix this myself or just take it to a shop? Some kind of tap tool would probably fix it, but since it's the beginning threads that are boogered it'd probably have to start from the inside of the cylinder. I really don't have a clue as to how to approach this.
Well, this past weekend that same plug blew out of cyl 4. Inspection reveals a coil and boot jammed up underneath the fuel rail and a plug that I fished out without any turning. When I go to install a new plug it just sits on top of the threads and turns without going in. So I guess what's happened is that the plug rotated most of the way out but when it got to the last couple threads the compression blew it out the rest of the way, and that it's just the top few threads in the hole that are damaged. Inspection of the plug reveals that most of the threads are intact except for the 2-3 that are closest to the element.
So my question is...should I try to fix this myself or just take it to a shop? Some kind of tap tool would probably fix it, but since it's the beginning threads that are boogered it'd probably have to start from the inside of the cylinder. I really don't have a clue as to how to approach this.
Feb 12, 2019 | 11:40 PM
#2
THE BERMINATOR
Joined: Sep 2018
Posts: 1,200
Likes: 2
From: Michigan
The only thing I know of to fix a spark plug hole with is a Heli-Coil, but I don't know very much.
https://www.stanleyengineeredfasteni...thread-inserts
https://www.stanleyengineeredfasteni...thread-inserts
Feb 13, 2019 | 03:46 AM
#3
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Trailblazer
Joined: Jun 2015
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Yeah that's what someone else said I needed. Same guy said he's done a few and more often than not the helicoil itself comes out the next time you remove the plug. Also suggested just replacing the head with used or reconditioned. If the shop can just manage to redo the threads without a helicoil I could probably implement tightening that one plug into my weekly maintenance routine and just hope for the best.
I've heard of another system like helicoil called Time-Sert that has a solid sleve insert but I've not heard much about how successful it is.
I've heard of another system like helicoil called Time-Sert that has a solid sleve insert but I've not heard much about how successful it is.
Feb 13, 2019 | 06:47 AM
#4
Pro Rider
Joined: Jan 2016
Posts: 2,491
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From: Perrysburg Ohio
They do make taps for rethreading spark plug holes, the trick is getting them started correctly as it is the first few threads that are typically the problem. If the tap cant be started corrwctly then the head is removed so it can be tapped from the inside where threads are good and easy to start. Tricky job but very doable, I have had to do a few over the years.
Feb 13, 2019 | 11:57 PM
#5
THE BERMINATOR
Joined: Sep 2018
Posts: 1,200
Likes: 2
From: Michigan
I don't think I would even try tapping it from the outside. I know I'd screw it up.
The Heli-Coil has notches in it so you can stake it in. If you don't install them right they can come out. My dad used one on my brother's snowmobile and it lasted however many years it was until he sold it. It was better than new.
The Heli-Coil has notches in it so you can stake it in. If you don't install them right they can come out. My dad used one on my brother's snowmobile and it lasted however many years it was until he sold it. It was better than new.
Feb 14, 2019 | 03:45 AM
#6
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Trailblazer
Joined: Jun 2015
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Good hearing about that success with the heli coil because the shop doing the repair tomorrow says that what they use. Guy talked about using a green thread lock, which I've never seen or heard of, but said as long as you let it cure 24 hours or more it hasn't had one come back out. Sounds trustworthy anyway
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