Broken exhaust stud removal

[JHZR2]

I know I had a slight leak in my 1991 MB 300D. I could smell it when stopped, and my smoke machine confirmed it.

I took some time off today to remove the turbo and manifold. It was an ok job other than a few lousy bolt locations and a tight space.

Cylinder number five was all sooted up. This is where I had found the leak.

I thought there was mild seepage from the turbo gasket. I saw some signs of that too.

All the exhaust bolts were loose, or I should say, came out easily. One snapped, or was broken already. It was on the leaky cylinder.

It’s sunk in far enough that I don’t know how I’ll get it out. The engine is tilted to the side in all these euro cars with inline engines, so the hole is angled downwards, not sure I can even center punch it to get a drill to start. Need some kind of a drill guide I suspect.

Any recommendations on how to attack this??

 

[Trav]

Size is M8?

 

[JHZR2]

Size is M8?

Think so. Not home to measure now.

 

[Exhaustgases]

Head off job to do it right.

 

[JHZR2]

Head off job to do it right.

What’s to say I can’t drill and back it out?

 

[2strokeNorthstar]

Do you have a mobile bolt extractor guy? I got lucky and we do. Wasn't cheap but worth it. Alternative it watch YouTube. Welder seems to be the best approach

 

[JHZR2]

Do you have a mobile bolt extractor guy? I got lucky and we do. Wasn't cheap but worth it. Alternative it watch YouTube. Welder seems to be the best approach

I have never welded before. Seems like a skill I need to develop.

 

[spasm3]

I can't tell if its too far down to weld a nut on it. That works well, but i would not want to screw up the threads above it, if its too deep.

 

[JHZR2]

I can't tell if its too far down to weld a nut on it. That works well, but i would not want to screw up the threads above it, if its too deep.

I tried to thread a new stud in, as it seems like there is a thread there. I can just barely get the first portion of a thread in.

I don’t weld so I can’t do it diy…

Size is M8?

Yes.

Of course the studs I bought by part number are slightly longer…

All the studs came out very clean and dry.

It’s the second from rear so a bit less space. Just behind the stud I screwed in.

Not a lot of space. I doused some Gibbs penetrant in on the broken stud.

 

[Trav]

I can't tell if its too far down to weld a nut on it. That works well, but i would not want to screw up the threads above it, if its too deep.

You can do this one okay but need to guide the bit well, here is something that can be made at home depending on your equipment, these were done on a lathe, it is probably easier to just buy them.
Measure the depth of the stud hole using the new stud so you have a idea how much is left to drill. Use a cobalt drill at slow speed <500 rpm with cutting/ drilling oil that fits the hole without too much slop, once the hole is drilled move up the sizes in steps till you get to 6.5 - 7 mm then remove the thin remaining threads with an easy out, they will come out easy.

https://www.amazon.com/AUTOVIC-Stainless-Tensile-Drilling-Broken/dp/B0DB23N7HR

 

[JHZR2]

You can do this one okay but need to guide the bit well, here is something that can be made at home depending on your equipment, these were done on a lathe, it is probably easier to just buy them.
Measure the depth of the stud hole using the new stud so you have a idea how much is left to drill. Use a cobalt drill at slow speed <500 rpm with cutting/ drilling oil that fits the hole without too much slop, once the hole is drilled move up the sizes in steps till you get to 6.5 - 7 mm then remove the thin remaining threads with an easy out, they will come out easy.

https://www.amazon.com/AUTOVIC-Stainless-Tensile-Drilling-Broken/dp/B0DB23N7HR

I saw those. Issue is there isn’t enough exposed female threads to get one in.

I was thinking to either drill out a bolt to do just that, or re-Install the manifold and figure out some other bushing to guide it through the hole in the manifold as a heavier, more solid guide.

 

[Trav]

It only has to go in a few threads, no need to bottom it out, at least you can get the drill started straight.

 

[CleanSump]

You can also shorten it if there isn't room for the whole hollow bolt and get another 1/4"-1/2" for the drill.

 

[Opelman]

Left handed drill bits are a huge help in situations like this. Often times while drilling I've had the drag from the bit back the broken piece out. My cheap set was in stock at O'Reilly.

 

[JHZR2]

It only has to go in a few threads, no need to bottom it out, at least you can get the drill started straight.

I tried threading a new stud in. I couldn’t get a single thread in. If I do something like this, I’d probably lay the bolt head on the head to get the alignment.

 

[emmett442]

Not many special tricks here.

If the head is aluminum, welding will be the way to go here, given the tight space.

Else, you'll have to find a way to make room to extract with drill/tools.

 

[Cujet]

I am good with a TIG welder, that would be my first choice. If the head is off, getting a nice bead on top of the broken stud down that deep is not too difficult, just extend the electrode and use a thin welding rod. Could even use a tube and weld inside it. Then weld a nut to it.

However, that location is tough to work with. I could not easily do a good job without being able to see clearly. Also since the stud broke so deeply, it is likely seized in the aluminum. Drilling and EZ Out is less likely to work. And once you drill, welding becomes more difficult.

As you know, there are drill kits for this and they may work. I'd be more likely to use aviation tools and a bushing to center the drill.

 

[Pablo]

Left handed drill bits are a huge help in situations like this. Often times while drilling I've had the drag from the bit back the broken piece out. My cheap set was in stock at O'Reilly.

This.

 

[JHZR2]

I am good with a TIG welder, that would be my first choice. If the head is off, getting a nice bead on top of the broken stud down that deep is not too difficult, just extend the electrode and use a thin welding rod. Could even use a tube and weld inside it. Then weld a nut to it.

However, that location is tough to work with. I could not easily do a good job without being able to see clearly. Also since the stud broke so deeply, it is likely seized in the aluminum. Drilling and EZ Out is less likely to work. And once you drill, welding becomes more difficult.

As you know, there are drill kits for this and they may work. I'd be more likely to use aviation tools and a bushing to center the drill.

Yes, the bushing is really the key to getting started. Trying some options…

 

[JHZR2]

It only has to go in a few threads, no need to bottom it out, at least you can get the drill started straight.

Ok, I tried this out. Not sure why I couldn’t get a new stud to start to thread, but I was able to get a bolt set up.

Not perfect, looking for thoughts.

Went to my old time local hw store, got the shortest M8 bolt they had, and two small cobalt right hand bits, and an extractor (Cleveland brand USA made as I recall, so decent for $4).

I center punched, tap lubed, and tried to drill with the smallest bit - 3/32 iirc. It went a bit crooked.

Then to try to fix it, I went with the other slightly larger cobalt bit. These bits are great. It did help a bit I think.

As opposed to the stud, I got the bolt to go in, maybe a 1/4 turn(?).

So, now the question - do I do my pilot with a 3/32 right hand bits, or go find some left hand bits to use through this bushing?

And should I make a few more bushings like this, one cut big enough to fit the center punch, the others increasing in diameter?

Fortunately I am off for the Holiday, so I can go about this deliberately. Usually I have no time and squeeze projects between kids activities…