Replaced T-stat, one stud won't stay in...

Replaced the t-stat on my 2001 T4R (319k)- the top stud and the PS bottom stud came out when I loosened the nuts. I tried to hand thread them back in then place the housing back over them... the top nut tightens to 14 ft lb, but as soon as the PS bottom nut starts to get tight the stud loosens up. I took both out to compare and they are the same length so I'm not sure why one will seat properly and the other won't. I had it all buttoned up and started adding coolant when it began to leak pretty bad, jumped under to ensure everything was snug when I noticed the issue with the PS bottom stud "floating".

Any ideas as to why this last stud won't seat and let me snug the nut against the housing so I can finish this job? Concerned the threads in the block might be stripped.

A buddy of mine suggested epoxying the stud in place... not sure how I feel about that and admit I'm out of my depth on that one.

Would a helicoil repair kit be a good solution?

 

Sounds stripped to me if you can't torque it down.

You could try to chase a tap down the same size and see if it cleans up and you are able to torque it down first.

I prefer timesert over helicoil but its only for this I think either would be fine.

 

Thank you. I grabbed a helicoil kit... any particular reason you prefer timesert? Going to grab new studs and nuts, too... figure it couldn't hurt.

 

Timeserts are soild while helicoils looked like wire coiled up.

I've always felt timeserts were stronger. Couple occasion I've had the helicoil fail on me when torquing down a bolt. Couldn't get it tight enough.

 

I literally just did a helicoil with a little loctite red. Perfect. Heli coil will work fine

 

Awesome- thanks for the responses. Going to try the least to the most invasive solutions- cleaning + new stud and nut, thread chaser (AZ has one I can borrow), helicoil. Will followup once I've got it up and running.

 

Replaced the original stud, I can now torque it down!! However, there is still a slow leak...steady trickle. Gasket not sealing? Dirty mating surface?

*just had to move the ground between the nut and housing