Here's an interesting one for you guys...

In the process of completing ,my 4th plug replacement on a 2003 X Type. Ordered plugs for next day delivery and figured I'd get a jump on the project by removing everything to access plugs so when they arrive it would be go time. I removed old plugs to inspect and hand tightened back into head to prevent debris from entering cylinder. Plugs arrived yesterday and went to complete job, started with removing old plugs again. Went to install new plugs and was not able to get threads to bite. Tried all plugs in all cylinders, then went to get the old plugs and was unable to get them to bite either. Inspected old plug threads for signs of thread damage (there was none, just some carbon and anti-seize). Froze new plugs overnight hoping to lower tolerance and get a thread bite, No Luck... As of now, neither new or old plugs will thread back into any cylinder???

*I have checked for proper plug selection - All Good (14mm x 1.25 thread)
*No signs of thread damage in the head as I would suspect there would be evidence left in the threads of the old plugs - Appear to be all good (wire brushed threads and seem to be only carbon and old anti-seize)

Any thought???

THERMO?

 

And to clarify, not an issue of stripped threads where I cant get the plug to tighten. I simply cant even get the plug(s) to start threading...

 

When I am faced with this type of thread catching issue, ie when nothing has changed, I always seat the plug by first lightly turning it anti clockwise by hand and I usually
can feel it seat properly when I have the correct angle. Then I turn it clockwise.

When I cannot use my fingers I will use a socket with an extension so that I can see the angle I am applying and still pay attention to the "feel" of seating properly.

This happens to me on my boat engine a GM 5.7 liter where I cannot see the plugs easily unless I risk breaking my ribs.

 

Resolved... I guess sometimes if you over analyze the situation you miss the simplest of possibilities. After racking my brain to come up with a logical reason for plugs not threading, I threw the plug socket out of frustration. Turns out the "new" socket allowed the plug to sit to deep inside and not allow the threads to reach before bottoming out on head. Back to the old trusty!

 

I bet that was annoying!

It can be easier to get them threaded if you use some thin tubing attached to the thin end of the plug. Doesn't provide much torque but you don't need much to get the thread started.

 

zerochills, you got to the solution before I could post it. I was going to ask how deep the plug sits in the well. Doing the trick that jackra stated also helps sometimes as you can feel the thread drop off and then you know that a slight turn will start the thread engagement.