Broke a exhaust stud

[guage]

This is on an 87 300SDL that I was replacing the exhaust flex coupling.
I removed both exhaust manifolds. and all of the turbo charging air cross over piping.
On reassembling the manifold the stud nearest the firewall snapped off, leaving the remaining stud recessed about a 1/16" in the block.
My luck it’s the only one with limited access to it being near the firewall, wheel well housing and the tranny dip stick.

Looks like I need a trip to sears for a small 90 degree headed drill and counter clockwise drill bits & easy outs.

Any one ever dealt with this that may offer some helpful advice.
Thanks
Guage
I'll get one of those telescoping mirrors too.

[Johnhef]

I'm dealing with this currently on my 87 300D, albeit mine was the third stud from the front. My extractors suck. It's been 4 weekends on it now and I still haven't got the damn thing out.

[boneheaddoctor]

Originally Posted by Johnhef

I'm dealing with this currently on my 87 300D, albeit mine was the third stud from the front. My extractors suck. It's been 4 weekends on it now and I still haven't got the damn thing out.

And like the thread on OD right now this is exactly why Mechanics charge book rate even if many can do it faster......the law of averages dictates overy once in a while a nightmare like this pops up.....I keep m fingers crossed...I have to pull exhaust manifolds off my 6.2 diesel in my truck as I am putting turbo manifold on it and a 6.5 turbo setup. And thats even more awkward than what you have to deal with.

You engine must not be leaking enough oil from the valve cover...otherwise you would be able to take that bolt no questions asked..

You might inspect all the other ones as well and see if any need replacing while they are still in 1 piece.

Good luck...

[guage]

I'd feel a whole lot better about doing this if I could just get
that stud center punched before try'n to drill it out.

[billrei]

Originally Posted by guage

I'd feel a whole lot better about doing this if I could just get
that stud center punched before try'n to drill it out.

I just removed 3 studs from M117 aluminum heads I am working on. Drilling into the exact center of the stud is absolutely critical especially in aluminum heads. If the drill goes off center it will break through the stud and take the path of least resistance into the aluminum at which point its pretty much FUBAR. I have also found that stud removers are pretty much useless and usually break and leave a hardened piece of metal in the center of the stud, once again a FUBAR deal.

Fortunately I have the heads off my car. To aid in drilling I made a drill guide out of a steel block. For 8mm studs I find a 1/4" drill bit works good. I drilled a 1/4" hole in the steel and another 5/16" hole that aligns with the opposite stud hole. I bolt the plate to the head and align the 1/4" hole over the broken stud. I apply a little superglue to the edge of the plate to help keep it from moving. I then drill out the stud using a sharp 1/4" drill. Once the stud is drilled I go in and remove whats left of the threads. Sometimes I can pick out a strand of thread and pull and it spirals out of the hole leaving nice clean threads. I finsh up by chasing the thread with a tap which removes any remaining thread material.

In the case were you still have the heads on the car I wonder if there is any way you could use the exhaust manifold as a drill guide. Go to a hobbly shop and buy some 5/16" OD brass tube with a 1/4" ID. You can use a short piece of tube to center the drill in the manifold. I don't know if you can get the clearance to do something like this. One thing I do know, trying to just drill out a stud unguided with a drill will 90% of the time result in bad news... You feeling lucky???

[P.E.Haiges]

billrei,

I noticed you used the term "chasing" the thread when using a tap to clean up the threads in a threaded hole. This is not an appropriate use of that term.

FYI: Chasing a thread is done on a lathe where the gears and screw drive of the lathe determine the pitch of the thread.

P E H

[billrei]

Ah no, for using geared lathe the term is "cutting" a thread. The art of thread chasing for fine optical threads were usually "chased", in the classical meaning of the term. In other words, they were cut with a multi-point, freehand tool. They didn't make taps or dies for large-diameter, super-fine-pitch threads. Chasing a thread is quite an interesting skill, but it's not hard to learn from what I hear.

But your point is taken. I cleaned the threads with a tap.

[aklim]

If you get out of this one intact, I would say that in future, you need to chase the threads with a chaser and then use some anti-sieze

[Brian Carlton]

Originally Posted by billrei

One thing I do know, trying to just drill out a stud unguided with a drill will 90% of the time result in bad news... You feeling lucky???

Reminds me of a project replacing the tankless coil on my furnace. Now, these bolts (no studs) have been in the cast iron for over 30 years. What's the chance that they come out without breaking them?

Well, I heated every one of the heads red hot and then went to town. No possibility of getting any penetrating oil in there because the heads are in the way. There are 14 bolts holding the plate in place.

With extreme patience, I removed 11 of them and broke 3.

With extreme patience, I drilled carefully on center and slowly increased the size of the drill up to the minor diameter of the thread. Bolts still would not release. Then, I managed to start the tap on the existing cast threads and cleaned out the remaining bolt threads.

What's my odds of doing all three? Managed to do it. No damage to the cast iron.

I cannot imaging trying this with an aluminum head, especially in the situation where you cannot position yourself directly in front of the hole. The odds of success are probably less than 10%.

[WANT '71 280SEL]

Do I absolutely HAVE to remove the rear manifold portion to replace that exhaust pipe? Mine is leaking as well and I'm afraid of breaking something.

Thanks
David

[Jim Anderson]

I had a piece of road debris hit my header pipe hard enough to dent it and break an exhaust stud. I borrowed a 90 degree drill from work but I saw a 90 degree adapter, from Harbor Freight I think, for a lot less. I also kept pieces of a broken mirror that helped. I got real good working backwards. The stud is probably just sitting there and will probably come out real easy, probably, mine was. But I did have a bracket bolt in my iron block break, then break the ez-out too. I got that out with a Dremel and a thin chain sharpening stone. I got real good working through a mirror.

The hardest and most important thing is to get perfectly centered.

[billrei]

Originally Posted by Jim Anderson

I had a piece of road debris hit my header pipe hard enough to dent it and break an exhaust stud. I borrowed a 90 degree drill from work but I saw a 90 degree adapter, from Harbor Freight I think, for a lot less. I also kept pieces of a broken mirror that helped. I got real good working backwards. The stud is probably just sitting there and will probably come out real easy, probably, mine was. But I did have a bracket bolt in my iron block break, then break the ez-out too. I got that out with a Dremel and a thin chain sharpening stone. I got real good working through a mirror.

The hardest and most important thing is to get perfectly centered.

Jim,

I think your stud came out easy because it broke because of impact not because it is corroded in place. In fact the impact might have helped loosen the threads up. It does not help that these studs seem to me made out of recycled Trabants with no Cad plating to prevent seizing.

[barry123400]

Really like ideal of using exhaust manifold as guide with sleeve but you may have to remove head unfortunatly. Was toying around with how i would handel your problem and to be absolutly truthful that approach did not occur but seems the best to minumize additional damage if you are careful. Really did not like the sound of your first post as thought trying to get it may work with head on engine but required just too much good fortune.(win any lotos this week?) Have done a lot of broken fasteners in past myself. The only other thought i had was you may be able to rotate complete engine somewhat in bay to get better access. If shank of stud was not rusted thin there is too good a chance that the threads are really seized hard in my opinion. Normal approaches may strip aluminium threads out to boot. Last thought was heli coil repair if you mess up threads. Should be enough material in area. But then again an easy out may do it although questionable. But if you break easy out off it may become a real mess.

[WANT '71 280SEL]

So removing the stud wasn't the hard part? Did you just over-tighten the stud so it broke?

Thanks
David