Never wash with walnut sand.

Never use walnut sand to clean engine carbon deposit. As the name implies, it is to grind walnut shells into powder and use high-pressure air to make walnut sand produce impact force to remove carbon deposits. Because the hardness of walnut sand is relatively low, it will not cause damage to the engine. But old drivers must be careful not to use walnut sand to clean up carbon deposits, because high-pressure air guns blow walnut sand into the combustion chamber, which is difficult to remove. If it accumulates on the valve, it may also cause the valve to close loosely. I think BMW first uses walnut sand cleaning technology to eliminate carbon deposits, which is very effective for cleaning engines. In addition, there are dry ice blasting, hanging bottles to remove carbon deposits, special cleaning solution for carbon deposits and peach sand cleaning method to remove carbon deposits. Tip: Cleaning up carbon deposits is like cleaning up a range hood with serious oil accumulation. When cleaning, you can clean the air inlet first (avoid entering other items), and then clean the air inlet valve carefully. When using sandblasting pipe/gun, keep running to ensure thorough cleaning. Patience and carefulness are the keys to this method.