Exhaust Manifold Stud Question

[Twright]

I am doing some work to the back of my 1997 M3 and I needed to drop the exhaust. I chose to split the exhaust at the outlet of the exhaust manifold. I successfully removed the exhaust but, unfortunately, broke off 2 of the studs at the exhaust manifold outlet.
My initial try at pounding out the broken studs from below has been unsuccessful.

Am I better off dropping the whole manifold off from the head so I can get to the broken studs, or am I just going to break off MORE studs at the head?

[R Shaffner]

It's amazing how something so simple, like removing a couple of nuts, can be such a PITA. As I understand it, the steel in the studs gets real hard and brittle from all the hot/cold cycles. When I tried drilling them out, the studs would dull the best bits I could find (and it was impossible to keep oil on the bit while upside down). And when I pounded on the stud with a hammer I was worried about hurting the head side.

I finally found this solution that worked for me:
https://forum.e46fanatics.com/showth...=894389&page=2

I did it with the manifold on the car. I had to make some other cuts/grinds in the puller to get it to fit, but once it fit, the studs pushed right out.

I ordered new studs, which was an absurd waste -- they're too long to fit back into the holes from the top side. So I just bought high grade nuts and bolts, and put nuts with washers on the top side.

Good luck!

P.S. I might still have the ground-down puller, which fit my M62TU like the pics in the link above. I can send it to you for the cost of shipping, if you agree to return it when done. Just send a PM.

[pbonsalb]

There are aftermarket repair flanges that are hinges or two piece that might work. Would probably need a cobalt but to drill out, maybe a whole box, starting small and going up a few thousands at a time. I did thus once years ago on a 328i project car.

You can also buy an aftermarket midpipe. I forget who makes them. Maybe magnaflo? Maybe Bimmerworld sells one.

[NeilM]

I have no experience with getting the broken studs out, although a torch is usually your friend with such things. Hammering them with the manifolds on the car may not be effective because of flex in the manifold. That tool does look like a good approach though.

But a +1 one replacing them with nuts and bolts once you have. Many years ago when installing aftermarket headers I substituted stainless steel bolts (used with the stock copper-flashed nuts), and they've worked well for me ever since.

Neil

[Braymond141]

The studs are inconel. According to the machinist forums, you want to drill to size once with a high speed steel bit. If you drill small and work up in size, you work harden the metal.

Some are press fit, some are welded up top on the head of the stud. Sounds like you’re dealing with welded versions. Press fit you can get out with a C clamp.

[hc1001]

the studs on the head back out if the nut is seized. They shouldnt break. I would take the manifold out.

[Hova]

I wouldn't hammer them out. Hammering only puts the stress on the aluminum threads in the head, I would be afraid of the head stripping.

I pressed my broken stud out similar to the E46 post done. Just make a simple press tool like that, while doing so. I wouldn't drill this, it's going to be a pain to get a drill in that tight of a spot. If you choose to drill this, please wear a face shield.

I used a stainless steel bolt through the manifold as a substitute as well.

https://www.amazon.com/Nickson-17350.../dp/B000COX90M

This might work too, or hell even a big enough c-clamp might work. Use a cup or larger nut than the head on the top, and press from below.


Inconel has a similar expansion rate to stainless, but heat would still be your friend here.




Other option is to take out the manifold.

[hc1001]

Manifold outlet, not the head outlet. He’s referring to the 6 total studs that connect the mid to the manifolds.

He asked "Am I better off dropping the whole manifold off from the head so I can get to the broken studs, or am I just going to break off MORE studs at the head?"