To get it off you could TRY some waterweld or J.B. weld (waterweld is a lot more solid)
J-B Weld Company - WATER WELD Product Information
This is what I would do first, it might save you a big headache of tap & easyouting the bolt.
Take the pump back off, and if you have to take off the grill and accessories then so be it if you need the room. Look at the broken bolt and align it with the broken one in the block (so the pieces fit together) mix up some waterweld and put a small amount (so it doesn't ooze out and get on the block, but stays in between the two bolts) You might want to experiment with a different bolt so you get the amount down. Once you get the amount down mix a new batch (hardens in about 10 min.) line the bolts up and put the waterweld on the bolt in your hand then line it up and stick it in the hole, keep some pressure on it so you know it's contacting the inner bolt.
Here is the hardest part. You will have to wait (I'd wait 24hrs) then go out and see if you can back it out with a ratchet and socket. Chances are you will. I used waterweld to hold in a sparkplug in an old subaru and it lasted TWO YEARS until I sold the car.
Good luck,
Take it SLOW!
You can also use some sort of lubricant on the outside of the bolt going in (just don't get it on the weld spot) in order to help the waterweld to not adhere to the block if some should ooze out.
Last edited by sevenmalards : 03-21-2008 at 01:03 PM.