How to Clean Inside an Engine Block

Written by amelia allonsy
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How to Clean Inside an Engine Block
The inside of an engine block may need to be cleaned if it has accumulated dirt and grease. (Auto Engine image by Andrew Breeden from

If your car's engine has accumulated dirt, sludge and grease over the years, you may need to clean the inside of the engine block. Without proper cleaning, this accumulation can damage cam shaft bearings, crank shaft bearings and lifters. It can also block the oil galleries, restricting oil access to the vital parts of your engine. Cleaning the inside of an engine block is a difficult job that must be performed with the engine out of the car and mounted on an engine stand. After cleaning and reinstalling the engine in your car, you will notice an improvement in your engine's performance.

Skill level:

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Things you need

  • Engine stand
  • Power washer or garden hose with spray nozzle
  • Engine degreaser
  • Stiff-bristled brush
  • Brake parts cleaner
  • Laundry soap
  • Cleaning rags
  • Lubricating oil spray
  • Air compressor
  • Automatic transmission fluid
  • Motor oil
  • Plastic bag

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  1. 1

    Mount the engine to an engine stand and connect the power washer or garden hose to a hot water source.

  2. 2

    Spray the engine block down with engine degreaser allowing it to soak in for the amount of time designated on the product label.

  3. 3

    Loosen built-up dirt and grime on the engine block with a stiff-bristled brush. Spray brake parts cleaner into the oil galleys, freeze plug holes, lifter bores and cylinder bores to loosen the accumulated grease.

  4. 4

    Scrub the engine block with the stiff-bristled brush, laundry soap and hot water while maintaining a constant flow of water over the engine to prevent rust. Use soft rags to clean the cylinder bores and smaller brushes to clean out the lifter bores and oil galleries.

  5. 5

    Rinse all soap from the engine block and immediately coat all interior and exterior surfaces of the engine block with a lubricating oil spray to prevent the rusting process. Spray the inside of the block, cylinder bores, lifter bores, oil galleries, bearing journals and saddles.

  6. 6

    Dry the inside and outside of the block by spraying with the air compressor. Add another coat of lubricating oil spray.

  7. 7

    Apply automatic transmission fluid to paper towels and wipe the cylinder bores to clean them. Repeat until all dirt and grime is removed. Coat the cylinder bores with clean motor oil and cover the engine block with a plastic bag until you are ready for paint and assembly.

Tips and warnings

  • The cleaning process may need to be repeated two or three times until all built-up grease and grime are removed.
  • A power washer may be more effective at spraying away dirt and may reduce the number of attempts necessary to clean the engine.
  • This job may require two people.
  • Avoid using harsh abrasives like scouring pads and steel wool, which can damage machine surfaces.
  • Always wear safety goggles and rubber gloves to avoid contact with chemicals.

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