Topic

Unfortunately, as anyone who works on cars in general, and MGs especially, will tell you, a 20 minute job on your car can easily change to a daylong job simply due to a snapped bolt.

I recently fitted a modified alternator adjuster, which was a 20 minute job, until this happened when I removed a bolt.

Probably one of the worst scenarios possible. You cannot get the new bolt in as the remainder of the bolt is still in place. The bolt has snapped below the neck of the hole, so that you cannot use grips to try and turn the remaining stud. Also, in this case, it is in a blind hole, in the engine casing, with suspension parts in the way.

Sometimes it is possible to use heat to try and loosen the grip of the broken bolt, but in this case, the aluminium has a low melting point so isn’t really an option.

First thing to do in this case is spray some release oil in and leave to soak. This should help loosen the grip.

Next, using a centre punch, place a pop mark in the centre of the broken bolt shaft. There are two reasons for this. First, it gives the drill bit an accurate place to start the drilling process. Without this the drill will just skid around and you will probably end up with an off centre hole. Secondly, the shock of the hammer blow will transfer though the bolt and help break any corrosion and weaken the grip.

What you will need for this is a drill, some suitable drill bits and a set of easy outs.

Easy outs are hardened tools, a bit like thread taps, but they have a course thread which rotates in the opposite direction to the bolt you are extracting.

Using the drill, start off with a pilot drill and drill to the depth you need. Try and keep the hole central and in line with the direction of the snapped bolt. Use plenty of oil to lubricate the drill bit and increase the size of the drill bits and the hole until you achieve a hole size that will let you use the largest easy out without encroaching on the existing threads, as this could damage the threads you need to keep.

Once you have the correct size hole, you should insert the easy out into the hole, applying pressure and turning it anti clockwise.

The easy out will start digging in and grip the remainder of the bolt.

If you are lucky the damaged bolt will start turning and you will be able to carefully extract the remains. If you find that the easy out isn’t gripping enough and just turning in the hole then you need to apply more pressure or, give a sharp tap with a hammer to help it dig in.

You may also find that the easy out grips well, but the damaged bolt won’t turn. Only apply as much turning effort that you feel comfortable with. The easy outs have been known to snap off if too much force is applied. You will then have a nightmare as the bolt will still be stuck in place but the hardened steel easy out will also be stuck, and that will not be easy to drill out.

If you have succeeded then this will be the result

If you kept the hole smaller than the threads and didn’t go off at an angle, the threads will be undamaged and ready for the new bolt.

If all else fails, you can drill out the existing bolt and threads and use a thread repair system, such as Helicoil or Recoil. http://www.the-t-bar.com/forum/22-cjj-s-guides/90584-how-to-fix-a-damaged-subframe-thread

Great advice as always from cjj

I have to laugh. Haha!
That same bolt snapped on me when I was doing the same job!
Amazing that a steel bolt will snap even though it's threaded into alloy.

I attempted to do the same as Clive. Unfortunately, my easy out snapped in the bolt.

I ended up drilling and tapping a new hole in the engine casing.

I was pretty surprised it worked to be honest. I always think if a bolt is that seized that it wont move using the bolt head, what chance do you have with an easy out.

David Aiketgate wrote: wrote:

Amazing that a steel bolt will snap even though it's threaded into alloy.

I think thats the problem, especially where the alternator is, prone to a spraying of salt mist from winter roads.
Rather than getting a coating of oxidation we get galvanic corrosion - https://en.wikipedia.org/wiki/Galvanic_corrosion

I am now really looking forward to fitting my alternator adjuster !!!!!!!

CJJ another great 'how-to' and I really appreciate the time you take to take photos in the middle of a job - especially one that is not going well! You must get through a lot of nitrile gloves. I'm using copper grease on most bolts I replace in the hope that I'll avoid future issues although I'm not sure what galvanic action this might promote with steel, alloy and road salt.

Richard

bryan young wrote: wrote:

I am now really looking forward to fitting my alternator adjuster !!!!!!!

It'll be fine Bryan....Just be very careful extracting the offending bolt.

cjj wrote: wrote:

I was pretty surprised it worked to be honest. I always think if a bolt is that seized that it wont move using the bolt head, what chance do you have with an easy out.

And looking at the bolt stub, the thread looks perfect... Go figure!

I wondered if the bolt had been fatigued by the forces from the alternator.

What do you do, when your easy out tool, snaps off in the bolt.

I can't drill it out, snapped off flush and using a cold chisel gotten no where.

This is the Manual tension allen bolt I'm trying to remove.

Personally, I'd give up and fit the bottle screw alternator adjuster which removes the need for the stupid adjustment bolt that always rusts solid.

Richard