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How to Drill Out a Broken Exhaust Stud

The bolts and studs used to assemble a vehicles exhaust system and connect it to the manifold are exposed to extreme temperatures while the engine runs. Because theyre on the underside of the body, theyre also constantly exposed to rain, ice and road salt. Given this operating environment, its sometimes a wonder exhaust studs dont always break while being removed.



When an exhaust stud does snap, however, there are a number of approaches to removing the broken shaft. Start with the first, and keep trying until the stud finally comes out.

Instructions

Heat Method

1

Expose the shaft of the broken stud. Check to see whether there is enough length for a secure grip with a pair of vise grips; if not, go to the next method.

2

Heat the surrounding metal with an oxy-acetylene, propane or MAPP torch. Play the flame over the metal all around the stud, but do not heat the stud itself; you want to expand the metal holding the stud to make the bolt hole larger while leaving the stud its original size.

3

Clamp a set of vise grips securely on the exposed end of the stud, and turn the stud counterclockwise. Do not apply excessive force, which might damage the stud further. If the stud moves slightly, apply more heat; if not, move to the next method.

Left-Hand Drill Method

4

Grind the exposed head of the stud flat with a grinder. This will help prevent the drill bits from slipping off center. Liberally apply penetrating lubricant to the broken stud.

5

Punch a dimple at the center of the bolts surface with a hammer and metal punch. Drill a pilot hole into the center of the bolt with a 1/8-inch bit. Keep the hole centered and straight.

6

Reverse the drill, and load a left-hand drill bit 3/16 to 1/8 inch smaller than the diameter of the stud. Drill straight into the pilot hole with the left-handed bit to avoid accidentally cutting the metal surrounding the threads.

7

Allow the left-hand bit to loosen the stud by its own rotation. Repeat the process with a larger left-hand bit or bits until the stud comes free. Once free, lubricate the hole, and clean out rust. If the stud still will not come out, move to the next method.

Drill-Out Method

8

Choose a drill bit with a diameter slightly larger than that of the original stud, including its threads. The purpose of drilling a new hole is to remove all traces of the old, stuck stud.

9

Drill straight down the center of the stud, following the previous holes, to the full depth. This method will remove the old, broken stud entirely while leaving a straight-sided hole larger than the original. Clean all rust and shavings from the new hole.

10

Insert a thread repair kit such as a Helicoil in the drilled hole, following the instructions packaged with the kit. Use a replacement stud of the original size when reassembling the exhaust system.

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