How to remove broken bolts from an engine block

Written by kennedi rose
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How to remove broken bolts from an engine block
Broken bolts should be removed from your engine block. (engine image by goce risteski from

A broken bolt can cause the other, non-broken bolts to weaken by exposing the non-broken bolts to excessive pressure as the non-broken bolts try to compensate for the broken bolt. For this reason, it is important to remove and replace broken bolts from your engine block as quickly as you can.

Skill level:

Things you need

  • Wrench
  • Bolt remover
  • Metal-cutting drill bits
  • Drill

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  1. 1

    Punch the centre of the broken bolt with a hardened steel centring punch and a hammer. Ensure you create a visible indentation. This will guide the tip of your drill bit. Ensure, also, that the punch is perfectly centred on the thread of the broken bolt.

  2. 2

    Drill into the bolt using a metal-cutting drill bit, approximately 1/8th of an inch or smaller. This will be your starter hole. Drill it as straight as possible in line with the bolt thread.

  3. 3

    Measure the width of the bolt threads and buy an appropriately sized bolt remover at your local hardware store.

    A bolt remover is a tapered screw that is threaded in the reverse direction (counterclockwise). This allows it to screw in counterclockwise and, once it reaches the taper, unscrew the bolt.

  4. 4

    Enlarge the hole in the centre of the bolt to the size recommended by the bolt remover directions, which are found on the bolt remover packaging.

  5. 5

    Screw the bolt remover into the hole in the bolt in the counterclockwise direction.

  6. 6

    Nudge the bolt out of the hole by applying pressure with a wrench in the counterclockwise direction.

Tips and warnings

  • Only work on or near your engine when the engine is cool.

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