Stripped spark plug hole

hu5ker555 · Post by **hu5ker555** » 02 May 2025, 07:12

2008 S60 2.5T 245k

I've been in the process of trying to replace my spark plugs. In doing so, I've found that the threads in cylinder #1 have become stripped and I'm having a hard time getting a new spark plug seated. I've tried various ways to try and lock the plug in place, but it seems the spark plug just keeps getting loose, working its way back out under load, eventually leading to misfires and then actually losing compression out the top.

Anyone tried a helicoil insert or something similar? I've seen some youtube videos on it.
https://www.youtube.com/watch?v=M8s-xcM ... =17&t=169s

One concern I have is how to make sure that the piston is at the bottom so that the thread cutter doesn't impact the piston?
Any other ideas/suggestions?

Post by **chrism** » 02 May 2025, 07:38

Use a plastic straw as a “depth gauge” to tell if the piston is near the bottom of the stroke. If you think the piston is near the top, pull out the straw and click the starter a smidge. Then insert the straw again and see if the piston rose or dropped. You may have to do this a few times in order to find something near the bottom of the stroke.

Post by **volvolugnut** » 02 May 2025, 07:53

I did not watch the video, but use lots of heavy grease on the cutting tools to hold the metal cuttings.
volvolugnut

dikidera · Post by **dikidera** » 02 May 2025, 09:01

Grease absolutely helps in cleaning up the cylinder/top of piston.

Post by **cn90** » 02 May 2025, 09:36

Timesert is the key.

Post by **BlackBart** » 02 May 2025, 14:00

volvolugnut wrote: 02 May 2025, 07:53 I did not watch the video, but use lots of heavy grease on the cutting tools to hold the metal cuttings.
volvolugnut

I was about to ask, how do you keep the shavings out of the cylinder??

Post by **matthew1** » 02 May 2025, 14:35

You could fashion a narrow vacuum tube to a shop vac and pull out shavings that drop onto the piston.

Post by **Blacklab467** » 02 May 2025, 15:55

I’ve used Heli coils lots, I’d say that is your best option at this point besides changing the head. Heli coils work well and are inexpensive. I’d want the piston closer to the top so you don’t lose any shavings down the ports. Not Close enough that you hit the top of the piston though. Vacuum out the shavings when you’re done.

Post by **volvolugnut** » 02 May 2025, 19:03

matthew1 wrote: 02 May 2025, 14:35 You could fashion a narrow vacuum tube to a shop vac and pull out shavings that drop onto the piston.

Tape makes a great vacuum hose adapter coupler.

volvolugnut

hu5ker555 · Post by **hu5ker555** » 05 May 2025, 08:12

When installing a new spark plug thread insert, how important is it to rotate the crank so that the piston is down?
From some cutaways of the engine head, it looks like the piston motion wouldn't ever get that close to the tapping tool (sav-a-thread).
And perhaps having the piston at the top might make cleanup/vacuuming of the cuttings easier?