Another day, another Volvo gremlin...
So my Volvo has gotten more and more to sound like a tractor when I start it up in the morning, and I traced the noise to the junction between the exhaust manifold and the header. With the engine running, I can reach down there and feel the exhaust puff-puff-puff-puffing right there at the joint. I got myself a new gasket and a deep-well 15mm socket and went at it today, thinking it'll be an easier job than the cam seals I still have to do.

Then, this happened:


OK, so what's the standard procedure for dealing with this? Drill it out and get a new stud (pretty sure I don't have tools for that)? Something else?
And how do I get at the nut that's hidden behind the downpipe? From below the car, I can't get a good angle on it so the socket slips off. From above, there's no room for a wrench to swing, and now I'm paranoid I'll break that one too.
Makes me wish I had just sealed it with Heat-Wrap like I had a mind to in the first place...

 

I always used a shallow six point socket with a long extension to remove those nuts. With one stud twisted off, it may be easier to remove the exhaust manifold and take it to a machine shop to have a new stud installed. Drilling it out in-place will be a difficult job. Removing the exhaust manifold risks twisting off studs from head.

Its odd that yours twisted off. I live in the Chicago area and my '90 240 is so rusty that it will be going to the junkyard soon yet I've never had any problems removing the exhaust nuts. Did you soak them in penetrating oil prior to your attempt to remove them?

 

Is the stud into the metal of the header or just at the flange where the back side of the stud was welded on (leaving a place to put in a new through bolt? Studs that are pins (ie screwed into an engine block or other threaded port) can be drilled out and removed with an extractor tool, then the hole can be retapped for a new stud. It helps to have a lift to get access so this may be one job worth paying a shop with the right tools. I really doubt it would be more than an extra $100-200 at a local shop. If you want to try drilling out, make sure you use a high quality drill bit slightly undersized to the bolt. (ie a cobalt bit should work nicely)

 

EXACTLY what I want to avoid. I don't have the tools to do it myself, nor the money to take it to a shop. The socket I used was a six-point. I learned long ago not to trust a tough job to a multi-point.

Maybe the nuts on yours were properly dosed with anti-seize compound at some point? Dunno. For three days prior to attempting this, I would come home from work, let it cool down, then hit the nuts with WD-40, PB Blaster, and some off-brand silicone stuff. Not sure how well I covered them because that spot is damn awkward to fit a spray can into, triggering it with my thumb from above.
By way of experiment, I took the stud that twisted off with the nut still attached and soaked it overnight in PB Blaster, then gripped what was left of the stud in a Vice-Grips while cranking with a 15mm wrench. That baby is STUCK. The circle is complete, they are ONE. It would have twisted off no matter what I did to it.

By the way, how did you get off the nut that's behind the downpipes? I can't get at it from below, and from above, there's no room to swing the wrench.

 

I have no idea. It's a 1990 240DL 4-door, and I went through my Bentley AND Haynes books just to try and find out what size wrench to use. Neither of them had ANY specs about that particular spot on the vehicle. Looking up the parts at IPD and other places, it appears they are threaded pins, which encourages me a bit that it is possible to simply drill out and replace them.

LOL, it would cost me $65 just to have my guy open the hood and wink at it. He's a VERY good mechanic with a crack team backing him up and the only guy in town I'd trust, but his shop is admittedly a bit on the spendy side. I can afford a cobalt drill bit, I'll see what I can do with that.

 

OK, I figured I had nothing to lose, so I found an angle to hit the 3rd nut, and it came off with barely a whimper. Out came the culprit:



I went liberal with the anti-seize gunk and cranked down the nuts as best I could. Hopefully that'll hold until I can get the tools to drill out and replace the one that busted.
I'll need to get to that ASAP because now the side where the thing busted off is leaking, obviously. Maybe I should put some heat-wrap on there anyway...

 

you'd be surprised that you can use a regular hand drill with a carbide bit to drill out a stud. A trip to Lowes, Sears, Harbor Freight or a big box auto parts store and you should be able to find a stud extractor kit - check out the vid to see what one looks like