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Servicing a blowing exhaust manifold gasket or repairing a snapped mounting bolt on a Cummins ISX15 highway tractor? Learn the step-by-step professional workshop sequence to mount the M20195 template, drill out broken stud centers, and chase threads without pulling the cylinder head.

Why Freehand Drilling Destroys Cylinder Head Threads

Exhaust manifold mounting studs on Cummins ISX engines snap due to severe thermal stress, leaving behind jagged, hardened steel remnants recessed inside the cylinder head mounting holes. When a technician attempts to drill out these broken studs freehand, the drill bit naturally seeks the path of least resistance. The drill bit tip walks off the jagged center of the steel stud and bites into the softer surrounding metal of the cylinder head casting. Within seconds, the factory threads are destroyed, requiring costly Heli-Coil or thread insert repairs—or complete head removal and replacement. Utilizing a dedicated guided template system like the M20195 fixes the drilling axis permanently. By bolting a rigid alignment plate to the cylinder head using adjacent good bolt holes, the hardened steel drill bushing forces the drill bit to enter dead-center every single pass, preserving internal threads and allowing clean stud extraction in minutes.

The 5-Step Manifold Bolt Extraction Protocol

1. Teardown & Surface Prep: Unbolt and remove the exhaust manifold assembly from the Cummins ISX engine. Clean old gasket scale, soot, and rust off the cylinder head deck face around the broken bolt location using a wire brush and solvent.
2. Mount the M20195 Alignment Template: Position the M20195 template plate against the cylinder head. Secure the template tightly using the kit's mounting bolts anchored into adjacent intact manifold bolt holes. Verify that the guide hole aligns dead-center over the broken bolt fragment.
3. Spot-Center the Broken Stud: Insert the initial spot-centering drill bit and matching hardened bushing into the M20195 template hole. Apply cutting fluid and drill a smooth, perfectly centered pilot dimple into the face of the broken stud.
4. Core-Drill the Stud Shaft: Switch to the pilot core drill bit and matching guide bushing. Drill smoothly through the center of the broken stud shaft, periodically backing out the bit to clear metal chips and reapply cutting lube. *CRITICAL: Do NOT exceed recommended drill speeds; allow the cutting fluid and bit geometry to core out the steel cleanly.*
5. Extract Fragment & Chase Threads: Insert the extraction tool or left-hand extractor bit through the guide bushing to back out the remaining thin steel shell of the broken stud. Remove the template plate and use the thread tap provided in the M20195 kit to chase and clean the original internal threads. Inspect the threads, install a fresh stud, and reassemble the exhaust manifold with a new gasket set.

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