Stripped thermostat stud
 

Ah, the best laid plans of mice and sailors go often awry...

I started a big project on my A4 over the winter, replacing the water jacket side plate and stripping off most parts to clean and paint the old girl, all of which I will detail in a photo- and error-filled post sometime soon. It seems bad luck to post before I've actually got her running and floating again, and I've got a couple of issues to sort out first.

But on to my current issue- as I was reinstalling the thermostat and housing, I managed to strip the front stud. I can turn the nut a couple of times, after which it releases pressure and we start again. Does anyone have any thought on how to best remedy this?

My plan is to try to clean up the threads with a die and thread file and see if that will make it catch, but I'm not optimistic. If that doesn't work, the half-assed shade-tree mechanic in me says to add a bunch of gasket maker under the thermostat housing and rely on one full stud and the bit of pressure from the stripped stud to keep things together. The whole-assed shade-tree mechanic in me says to go down to a 5/16 die and move to a smaller nut on the existing stud. The over-engineer in me says to try to remove the stud with the head in place and replace it, although I suspect this will result in snapping it and having to go for a fancy new Moyer stud repair kit.

Any guidance would be appreciated. Launch is just a week away!

This is a common occurance. there are two approaches to fixing it:

1. Drill out the stripped hole and tap it larger. Install a special repair stud that has a larger diameter on the lower end. MMI sells a kit

2. Drill out the stripped hole and tap it larger. Install a threaded insert (not a helicoil, they can leak), and install a new standard stud.

This just happened to me a couple days ago. Got the rebuilt engine together, fired it up, then went back to retorque the head nuts after it was up to temp, and stripped one of the thermo studs out of the block. Got my stud repair kit on order, I'll let you know how it goes.

Yes they can! Don't ask :o

You don't say which end is stripped. From your description, I'd say the top end (nut to stud). If a new nut doesn't fix the issue, it's time for a new stud. Pull the old stud out of the block (leave head in place), run a tap into the block to clean the threads, then install a new stud with your sealant of choice (toss up whether I'd use Permatex brown stuff or JB Weld epoxy). Keep in mind that this isn't just a t'stat stud - it's also a head stud and has to be torqued to the same value as the other head studs.
Not a big deal.

Yes, it’s the top end that is stripped. I hadn’t thought about this also serving as a head stud (it’s obvious I know!), but that makes me reconsider my lazier approaches...

Oh... I assumed it was the bottom that pulled out, as the block gets thin from corrosion and there aren't many threads left hoiding the stud in. This is what usually happens.

So, forget what I said earlier. Just remove the stud and replace it with a new one.