Tom

Dear    Tom,

Q I have a problem of my own making. I was trying to change the

thermostat on my ‘97 Dodge Caravan, and I snapped the first bolt while
trying to loosen it. About a half-inch of the bolt came off, but the other inch
remained in the engine. I am a novice home mechanic and have never drilled
out and re-tapped a threaded hole. I called a local shop for a price and they
told me it would cost $78 an hour to do the job. He said it could take 15
minutes or 2 hours, which would be $156 in labor costs for a $1 bolt! I know
the alternator will need to be loosened and moved (to get clearance to the
right housing bolt hole). Can you give me some advice?

John—Springfield,   Ohio

John,

A Make sure the area you are working on is clear of obstruction. Any

component that is in the way should be cleared of the work area, alternators
included. Next, make sure you center punch the broken bolt so you can drill
in the center of the broken bolt. Use a drill that has variable speed control,
and drill slowly and deliberately holding even, steady downward pressure on
the drill. I suggest you get a titanium drill bit set and start with a small bit,
working up one size at a time until you are one size away from drilling out
the threads. Once you have gotten to this point, take a tap that fits the hole
and thread size and start running the tap into the bolt hole. Slowly and
deliberately turn a half turn, then back out and turn a little deeper, then back
out, and so on. The tap will cut the old bolt out and find the original threads.
Use lubricant and air (if available) to clear the hole of metal as you work.
This job can be done if you take it slowly and meticulously.