Impossible Downpipe Bolt - Options? Topic is solved

[justanotherhumanoid]

Okay, so I successfully (more or less) swapped turbos from the 14T in my '06 2.5T AWD to a rebuilt junkyard 16T. It all went remarkably smooth, with the exception of a single downpipe-to-turbo bolt that would not go in. I'm not sure if the threads in the junkyard turbo were damaged, or what, but the bolt stops rotating about 2 turns in, and while I'm able to apply enough force to keep rotating it, this results in the bolt threads getting pretty much pressed flat or stripped as I rotate it in. It's obvious that something is wrong with the threads on the turbo exhaust flange in this one hole. The other two bolts went in smooth as silk.

First I tried swapping bolts around, tried a spare bolt, etc. I tried a couple, new and used. I'm confident they were the correct hardware. No joy there.

I took out the other bolts, moved the downpipe out of the way and tried running a bolt in without any interference. Same thing. Get stuck. Removed it.

I tried cleaning the hole/threads out with brake cleaner and a pick, which didn't really do anything. I ran a sacrificial bolt in pretty hard to see if that would do anything, but it didn't change anything. I was pressed for time and had to get everything back together, so... what I have in there now is a small clamp made specifically for this application, but I don't like it there and I want to clean up those threads and use the original hardware.

What would you all recommend? I've never tapped a hole or used a thread chaser before, but I'm guessing that's what I need to do here. Any tips/guidance would be greatly appreciated.

That said, this clamp thing is strong as hell and I'm pretty sure it will hold it forever. I just don't like it there and it interferes with the heat shield.

Pics:

[abscate]

You could try a tap to clean up the threads but the other option is to drill it through up size slowly , and then through bolt/nut it, in stainless fittings

[jonesg]

If you snap a tap in that hole you'll be opening a can of worms, research how to tap metal before doing it.
I would first try running a short bolt through from the back side to chase the threads.

[darylrobert]

cut a V in an old bolt, lube it up and work it very carefully. if your not comfortable running a tap, ask a shop to do it

[volvolugnut]

Cleaning up a damaged thread is generally safer than tapping a new hole. Much less metal is removed. A harder choice is determining the proper thread size and thread pitch (threads per mm).
When tapping, always use a good lubricant. Use a partial turn in followed by partial turn out to break the metal chip. Then turn inward a bit more than the previous cycle. This in and out motion also burnishes the threads. If the hole is deep or blind (not a through hole) then turn all the way out and clean chips form the hole and tap before restarting. Never force the tap. Thread cutting is not much more than light torque.
volvolugnut

[justanotherhumanoid]

I was able to clean up the threads and get the proper bolt back in there using a tap and y'all's advice. Picked up a tap & die set. Did a practice run on the old turbo to verify I had the right tap size and pitch and to get a feel for the technique. I happened to have the downpipe off which gave me some extra room to work. Used cutting oil liberally and took my time. Also used an adapter which let me use a ratchet to turn the tap, since space was still pretty limited. Backed it all the way out to clean it off a few times and spray debris out of the hole as I went. Slow process but it went smooth.

Now the clamp is off, a nice new bolt is installed, and my heat shield is back in place. Great success and pretty damn satisfying after the frustration of fighting it so much earlier.

This tap and die set is a game-changer...

[MoVolvos]

I was able to clean up the threads... Used cutting oil liberally and took my time.

This tap and die set is a game-changer...

The old timers used Anti-Seize, not the copper type, to clean up bolts and chase threads.

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