My # 5 sparkplug keeps backing out to where it is really loose and about to fall out it allreadyhas once. I have replaced the plug and when i put it in it goes in tight not cross threaded and does not keep spinning it is tight but over 2 months it will back out again. Can i use thread locker on it to stop it from backing out?

 

Spark plugs don't "back out".

You probably have stripped therads and it seems like it wil tighten up, but is actually barely holding on, a couple heat cold cycles and it has loosened up from the one remaining good thread.

Helicoil is your friend here.

 

+1, nothing that could allow a properly torqued plug to back out unless the threads are fubar. You could TRY some loc-tite, but....I def wouldnt recommend it

 

I just want a easy quick fix for now the einge has 242,000 miles on it. This is something i would like to address when it is time for a rebuild but if i have to use a heli coil i will. What about trying to clean the threads? Also when you use a heli coil how do you keep metel out of your cylinder?

 

Unfortunatly you don't, though putting some grease on the tap, in that low area, will help catch a lot of the shards.

 

Make sure your spark plug socket isn't hitting the cylinder head before the plug is fully tightened...you think the plug is tight, and its not fully seated so it backs out gradually. If the threads were that shot, it probably wouldn't go in at all, much less stay for two months. I have seen this issue on LT1s and 4.3s. Try another socket or a wrench if you can get to it.