How to remove a broken bolt from a thermostat housing

Written by zyon silket
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How to remove a broken bolt from a thermostat housing
As the bolts heat up and cool down, they weaken and can break. (radiator humour image by John Sfondilias from

If the thermostat in your vehicle has stopped working, you have to remove the thermostat housing in order to replace the faulty component. However, this task can be made more difficult then expected when dealing with a broken bolt on the housing. As the bolts constantly go through a heating and cooling cycle, they can weaken; as a result, you can very easily snap the head of a bolt when trying to remove it from the thermostat housing. If the shaft of the bolt is stuck in the intake manifold, it must be removed before you can reattach the thermostat housing to the intake manifold.

Skill level:

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Things you need

  • Electric or cordless hand drill
  • Drill bit
  • Spiral flute screw extractor
  • Tap wrench

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  1. 1

    Drill a hole into the top of the bolt using an electric or cordless drill. The most common bolt for a thermostat housing is the 10-millimeter bolt. According to My Tool, the correct drill for extracting a 10-millimeter bolt is the ¼-inch drill.

  2. 2

    Place the spiral flute drill extractor into the tap wrench and secure the extractor by turning the knurled handle on the wrench. This tightens the extractor and prevents it from falling out during the extraction process.

  3. 3

    Place the drill extractor into the hole drilled into the bolt and turn the wrench counter-clockwise. The extractor will thread into the bolt. With subsequent turning, the bolt will back out of the intake manifold.

Tips and warnings

  • Spiral flute screw extractors come in a kit, and they are labelled for use with the correct drill bit. The most common bolt is the 10-millimeter bolt. Measure the head of the bolt to be sure you are using the right extractor.
  • Extractor kits are available from most popular hardware stores, home improvement stores and automotive supply stores, and they range in quality. Many extractor kits will also supply the tape wrench.
  • You can substitute the box wrench for a wrench with an adjustable end. However, it is important to have a secure grip on the screw extractor to prevent damaging anything around the thermostat housing.

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