99 ranger 4.0 v 6 replaced the thermostat and the housing , noticed the lower bolt when putting back would slip, friend gave a a time SERT kit installed but still drips feels like the time SERT or bolt backs out, can I apply loctite to the threads ??

 

No on the loctite, it won't help for the described issue, which is stripped threads so can't hold housing tight enough to seal it

Loctite is used to prevent bolts/nuts from vibrating loose after they are tightened, your bolt is not tightening

You will most likely have to redo the timesert or drill and retap the hole and use a larger bolt, may have to make the housing bolt hole larger

Common issue on these is OVER TIGHTENING the bolts so they strip
This type of thermostat housing usually has a rubber o-ring on or around the thermostat, it seals by using equal pressure on the 3 or 4 bolts that hold housing to the intake
These are just "snug" maybe 12-15ft/lb torque if that
Over tightening one bolt causes housing to warp slightly and you get a leak

So first thing is to get that bolt to "feel tight" if it doesn't seem to "get tight" then it's NOT, lol and can't seal the housing

Check the depth of that hole, use a smaller screw driver and insert it in the hole then compare that length to the length of the bolt
There may be a few threads left at the bottom of the hole that are in good condition
You could then use a stud with correct threads, that is long enough, and use Loctite on that one, then install housing and use a nut on the stud

Have also seen that done but using JB WELD to hold the stud in place since there were no threads, make sure to let it set up long enough or it will just spin

And DO NOT over tighten it