Can hot car brake pads be cooled with water?
2 Answers
Brake pads should not be cooled with water when they are hot. Here is some relevant information about brake pads: 1. Indicator: Generally, there is a protruding indicator on both sides of the brake pad, with a thickness of about 2-3 millimeters. This is the minimum allowable thickness for the brake pad. If the brake pad thickness is parallel to or below this indicator, it must be replaced. 2. Warning system: Some brake pads are equipped with wear limit warning systems, which can be mechanical or electronic. The mechanical type involves installing a small metal piece at the wear limit thickness of the brake pad. When the brake pad wears down to this point, stepping on the brakes will produce a harsh metal friction sound. The electronic type has a built-in circuit in the brake pad. When the brake pad wears down to the limit, a warning will appear on the dashboard, prompting the driver to replace the brake pads promptly. 3. Increased braking distance: If the brake pads are contaminated with oil or soaked with grease over a large area, the grease can penetrate the brake pads, altering their molecular structure and reducing their strength or even causing them to become brittle. This can lead to slipping, cracking, or other issues during braking, resulting in a longer braking distance. Therefore, brake pads contaminated with grease must be replaced.
Once after a long downhill drive, my brake pads were so hot they were smoking. Thinking to cool them down quickly, I poured some water on them. Later during inspection, I found a crack in the brake disc. The mechanic explained that this happened because the sudden cooling of the overheated metal parts caused excessive internal stress from thermal expansion and contraction, leading to the crack. This not only damages the disc but can also impair braking performance. Such thermal shock is especially dangerous after high-speed driving or heavy loads, potentially causing anything from brake shudder and reduced efficiency to complete failure on the road. So I learned my lesson: never douse overheated brakes with water. The right approach is to pull over safely and let them cool down naturally. Regular maintenance is also crucial—checking brake system thickness and condition to prevent issues before they arise. Even in emergencies like pulling over near a wildfire, it's essential to first park safely and wait a few minutes for natural cooling rather than rushing to intervene and risking worse consequences.
