When you run across this problem, you are faced with a major hurdle to overcome and many will suggest you beat the snot out of the center pin with a big hammer to break what's left of the bolt off.... and this usually ends up leaving you with a broken center pin or a useless carrier. Some will suggest to plunge grind into the pin to get at the bolt, but this is no easy task because of the tight space and at the very least, you'll need a new center pin.
However, I will describe in clear detail the CORRECT and EASY way to tackle this situation.
Here is a pic of the rear with an arrow where the bolt in question is located:
Here is a pic showing what a new bolt looks like (top) and what the broken bolt looks like (bottom) so you can see exactly what the broken piece you are about to deal with looks like:
Now here's the secret... a pic of the Extraction Kit you will need to order. It comes with a long drill bit, 2 threaded drill bit guides that thread into the hole the bolt came out of and 2 different easy outs. More information on where to get this kit later.
- First start by masking off the area to keep metal shavings from getting into the housing.
- Determine which threaded drill bit guide to use. This depends on how much of the bolt is left inside the carrier. Usually the shorter of the two is the one you'll need.
- After the guide is hand tightened into the bolt hole, mark your drill bit with tape so you'll know when you've drilled into the end of the bolt about a 1/4". Spray some WD-40 into the hole to extend the life of the bit.... and start drilling, taking care to go in as straight as possible.
After you get the hole drilled in the end of the broken bolt piece and remove the drill bit guide and rinse away any shavings by spraying some more WD-40 in the hole, you are now ready to use a small hammer to gently tap the square easy out into the hole you've just drilled. Most times you can turn the broken bolt out with just your hand, but sometimes you need to use a pair of pliers if it's a little tight.
Finally, here's a pic of the extracted broken piece:
The kit is made by a company called Fabbri Associates and here's the link http://fabbriassociates.com/
These kits can also be found on Ebay for around $30... best money you'll ever spend.
Hope this write up has been helpful.