how do you take a broken bolt out of a aluminun threaded area of a car?

Answer 1

if there is enough bolt sticking out you can use vise grips and clamp on and back it out, if not they make a bolt extractor kit for the drill that drills in and removes the bolt.
check your local parts store for that.

Answer 2

Having worked as a licensed mechanic for the last 30 years there is nothing more frustrating then broken bolts. Here are the things that I do to remove broken bolts:
First if you have access to a mig welder then you could try to weld a nut to the broken end. The heat generated by welding helps to free-up the bolt and then by gently twisting back and forth work the broken bolt free.

If you don't have a mig welder or the above action will not remove the bolt then it will have to be drilled. Use a left handed twisted drill (drill will have to be set on reverse) and drill a hole down through the centre that is of a size that a tool known as an easy out can be inserted into the drill hole. These tools are available at your local auto supply stores.

If an easy out cannot remove the broken bolt then you will have to drill the hole larger and re-tap the hole using a tap set. If the thread becomes damaged while trying to remove this broken bolt then a Helli-coil will have to be installed to replace the damaged thread. Helli-coil kits should also be available from your local automotive tool supplier.

Answer 3

U will need a tool, called Easy Out. It is designed for that purpose. You can find that at your auto parts dealer.