I recently got my leakdown tester adapter stuck in my spark plug hole when it disconnected from the tester as I was unscrewing it. I read people putting loctite on the hose threads, needle nose pliers, hammering screwdrivers, pulling the head, etc.

But I found something simple and easy: a new o- ring!

Put a new o-ring on the tester hose, and do not use any oil. Now screw that sucker into the stuck adapter and they should screw right back out!

My theory is that a new dry o-ring has more rotational grip than an old oily one, so that keeps the tester from detaching from the adapter.

I've seen this is a pretty common problem, and it worked for me so I figured I'd share. Good luck!

 

Good idea. Many adapters come with o-rings already installed for just that reason. This should be a sticky in the "good advice" section of the forum.