|WYG|SS

i got a 93 f150 4.9l 5spd. well like 5 months ago i had taken my truck in to get some stuff fixed and i asked my mechanic to look at this exhause leak i thought it was, so he tells me that they looked at it and found no exhaust leak, instead they found out that some of the spark plugs were loose. so he tightened them and torqued them. so now i heard the noise agian and one of them was loose and so i tightened it and now i think it may have worked loose again. could i use lock-tight on the threads?

whitetrucks

I wouldnt reccommend it unless you never plan on changing the plugs again.

but I think there is a product on the market that will do the same thing but with out the absolute permanence of lock tight

|WYG|SS

well i can buy the different strength lock tight. i would get the wrench loose one.

wde3477

Perhaps try another set of plugs? IMO, lok-tite is a bad idea for use on plugs, even if it's the low-strength kind.

|WYG|SS

i can try that. well to when i pulled the loose one out the gap was pushed in and the center part of the plug was starting to melt.

Kattumaram

....can't for the life of me imagine spark plugs working loose, particularly in a cast iron head.

I'd recommend against a thread-locker unless you get some double-platinum plugs good for 100K so there's no need for a few years to replace the plugs.

Torque for those plugs in that engine is fairly typical: 10-15 lb/ft. Who knows whether or not the proper torque has actually been applied?

The scheme I've used for fifty-odd years is this: Clean up all threads and make certain the plug sealing surfaces are clean and free of carbon. Apply a bit of thread lube to the new plugs and torque them in to the maximum recommended torque value. The plugs should run into the bores smoothly with no sense of catching or jamming right down to the point where they are bottomed-out; snagging or dragging indicates some dirty or damaged threads. If the plugs are difficult to turn, but otherwise uniformly smooth turning, then do a "running" torque of that drag and add that value to the maximum torque value.

BTW: If the plugs were loose and leaking, then lots of carbon and crap has built up on the threads and seats. If the mechanic simply tightened the plugs up with a retorque, then the carbon was still in there and the plugs will not seat properly.

kifels

Don't use locktight you will never be able to change your plugs again, that stuff will get hard as a rock with the amount of heat the plugs are exposed to constantly. check the plug that came loose does it have a washer on the threads? is it squished? check the threads on the plug. are those stretched? or worn down? I would also say try a new set of plugs, and make sure you use the washer they come with.