Thermostat
 

I have a 1997 f150 with the 4.6 . I was changing my thermostat and everything was going good in till I started putting the bolts back in to the housing . The bolt goes back in but won't screw in . It's like there is no threads there . Anyways if anybody has any advice I would greatly appreciate it.

Have you owned the vehicle since new?
The reason I ask is , we don't know if someone else messed up the threads or not.

You have a few choices though.
You could install a Heli-coil ,
There are some pretty good thread making compounds on the market,
If the threads are all gone and you have enough meat to thread a slightly larger hole with the next size bolt,

Are you sure the hole has no threads left? Could there be a problem with the bolt?

The threads was all gone . I had to retread it with a bigger bolt . Thanks for the advice .