What you’ll need to remove the broken bolt
Electric or air drill
Drill bushing.. something like this Drill Bushings | MSCDirect.com
This centers the drill bit in the housing bolt hole so you don’t get off center and damage the water pump, timing cover housing or engine block
5/32” Cobalt coated bit
EZY-OUT Screw Extractor Bolt Extractors | MSCDirect.com
Long shank 5/16-18 tap .. a T handle tap wrench will make things easier when turning the tap
Removing the broken bolt
1.) Remove the water pump, fan, fan shroud & radiator – you’ll need lots of room to get the drill positioned straight.
2.) Test fit the drill bushing in the timing cover housing – this assumes that the bolt broke off below the surface of the housing. If it is too loose, use some scotch tape wrapped around it to make a snug fit. The drill bushing helps center the drill bit up on the broken bolt so that it does not get off into the timing cover or engine block. If the bushing does not fit at least 3/8” into the timing cover, you may want to consider removing the timing cover and attacking the remnant of the bolt shank with a propane torch and Vise grips. If not, then find a drill bit big enough to drill off some of the remnant of the bolt shank until you can get the drill bushing in the required 3/8” or deeper into the timing cover housing. You will end up using the timing cover housing to center the large drill bit on the broken bolt shank. This is not the best plan, since the aluminum timing cover is soft and it would be easy to get the bit off center and damage the timing cover.
3.) Once you have the drill bushing in place, chuck up the drill bit and drill the broken bolt. Use lots of WD40 to cool the drill bit. If you break the drill bit off in the bolt, it is time for a tow trip the automotive machine shop. Drill bits and easy outs are extremely hard and cannot be removed by ordinary means. It takes a solid carbide bit and extreme care to remove a broken drill bit or broken easy out.
4.) When you have drilled about ½” into the broken bolt, then remove the drill bushing and use a hammer to tap the easy out into place. Then chuck up the easy out in a T handle tap wrench. Turn the tap wrench slowly counter clockwise and you will feel it dig into the broken bolt. If it starts to slip, tap on the tap wrench with the hammer to reseat the easy out into the bolt.
5.) Keep turning and one of three things will happen:
a.) The bolt will come out and your efforts will be rewarded.
b.) Or the easy out will continue to slip and more efforts will not make it grip. This means you get to remove the timing cover and attack the bolt remnant head on. That means you get to drill the bolt out to a thin shell & either re-tap the hole or install a helicoil threaded insert.
c.) Or worst of all, the easy out will break off it the bolt shank. Then it is tow time to the automotive machine shop and pain in the wallet.