Broken Bolt Repair

Extracting Broken Bolts and Studs


You suddenly find yourself with a wrench in one hand with part of the bolt or stud you were trying to extract, and the rest of it still in the manifold/head/block/suspension bit? Contratulations - you're about to have an adventure.

I've been there. After you've worked on old cars for long enough, it's inevitable. The most recent occasion was on my TR4A, where someone had used a piece of threaded carbon steel rod to replace an exhaust manifold stud. You *can* get the remains of the stud out without removing the head.

You will need:

  1. patience
  2. dremel tool with small grinder bit (carbide is best)
  3. patience
  4. heat wrench (propane, MAPP or oxy-acetelene torch)
  5. patience
  6. reversible drill
  7. patience
  8. collection of ez-outs and left handed drill bits to match, plus drill stops
  9. patience
  10. a drilling template
  11. patience
  12. sharp punch and hammer
  13. patience
  14. penetrating oil (I think Kroil is best)
  15. patience
  16. a properly sized tap
  17. patience
  18. a little luck

A scribe and a small round file may help. You might want some extra patience, too. If you get frustrated in the middle, take a break and come back to it the next day.

The starting trick is to get a hole drilled into the center of the stud. This is the point of the drill template - I made mine by copying the holes in a manifold gasket. Make the hole you're going to drill just larger than your starting drill bit size - I usually start at 1/8 and work up, but it will depend on what left handed bits you can find. You can make the template out of plywood; aluminum plate is better. You want adequate thickness to make sure that the drill bit is at an exact right angle to the manifold face.

Drill. Use the drill stops! You don't want to drill deeper than the broken piece. Make a good center punch to try to keep the bit from wandering (especially if you don't have a drill template). Chances are that you won't get the hole dead center, because gaskets aren't made perfectly; do the best you can. Go up in size until you are in danger of cutting into the threads in the head; inspect often with a mirror and flashlight (tip: point the flashlight into the mirror).

Use the EZ out. There are two sorts - straight fluted and twist fluted. I prefer the straight ones, because all the force is used to turn the broken stud, rather than twisting the EZout in farther. But the twist ones are more amenable to weird hole sizes. Chances are that you won't get anywhere with the EZ out, but try it anyway. Don't break it off, whatver you do.

Heat the area with the heat wrench, spray on some Kroil or WD-40, and wait. Repeat several times. This might help, it might not. Try the EZout again. Repeat until you're frustrated and ready to go on to the next step, or, if you're terribly lucky, the blasted thing comes out. (It may take several days of this cycle to succeed. If you're not in a hurry, this is the safest way. The hotter the torch the better - try to get the part red hot.)

There is a new generation of tools that combine left handed drill bit and ezout and even claim to center themselves. They're very expensive, so I haven't tried them yet. They just might make this job a little easier.

I will usually try a small impact wrench at this point: find an 8-point socket that fits over the square end of the ezout and blast away. This sometimes works. Don't be surprised if it doesn't. And, again, try not to break the ezout.

If you're now to the point where the next larger drill bit will start removing threads, you have to proceed carefully. Using mirror, flashlight and dremel tool, grind outward from the hole you've drilled. Eventually, you will start to see the ridges of the thread cut into the head poke through the stud material. You can get away with removing a smallamount of the crest of the thread - this will make the stud fit a bit poorer, but probably won't matter much. At this point, you can try using the hammer and punch to rotate the fractional piece of the stud in the threads.

You can also take the file to the hole and enlarge it, and then try the two above methods.

Finally, you can use the file (or a small grinding point on a Dremel) to remove the first couple of threads of the stud (using the scribe to pick the pieces out of the troughs of the manifold thread).

When you have achieved this state, you can start using the tap to remove the remaining metal. Best is a tap with a tapered start, so you can get some purchase in the hole you've drilled; once you've removed a bunch of the metal, you can switch to a plug-style or bottoming tap to clean out the deeper grooves. Chances are that the trapped material will break off in complete rings, which you want to remove - pull the tap and use a sharp object to try to clear these out before tapping more. You want to reverse the tap often in order to clear the shards. Use the tap to essentially tap a new hole - you want to go about 1/8 turn at a time, cleaning the tap every time. You'll probably lose the first couple of threads in the manifold, but that shouldn't matter much.

I spent three or four evenings in the process of removing a broken stud from Sarah's head. It was not pleasant, but it beat the hassle and expense of removing the head.

I have spent weeks getting a stuck tapered plug out of a cylinder head. Like it says in the list above, patience is important.

Oops again...

So you broke off the EZ out? Now you're in bad shape. Take the part in question to a machine that has a plasma cutter or an EDM (Electrical Discharge Machining) machine and get them to remove the remains. They'll cut that sucker out in nothing flat, very precisely. It probably won't even cost much, but you *will* have to remove the part in question.

If you're good with a welder and brave, you can try welding a piece of stock to the broken bit to give yourself some purchase to turn it all.

How to avoid this

When you get it all done: make sure you use anti-seize on the new studs before you install them, so you (or the person you sell the car to!) won't have to go through this the next time. On an exhaust parts, use brass or stainless steel nuts and lock washers, so they don't corrode in place (TRF sells the brass nuts, as do most auto parts stores; go to a marine supply for the stainless kit). ARP is starting to manufacture stainless studs for British applications, but I don't think they have any for Triumph yet.
Copyright © 1989-1996 Team.Net

This page brought to you by Chris Kantarjiev of The Dimebank Garage.

Last updated 28 February 1996 by cak

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