ASE Gasoline Engines (T1) Practice Test 2025 - Free ASE T1 Practice Questions and Study Guide

White exhaust smoke is an indicator of potential internal coolant leaks in an engine. When coolant enters the combustion chamber, it undergoes combustion, which produces white smoke as a byproduct. This is particularly evident during engine startup or when the engine is under heavy load. The presence of the coolant in the combustion process creates steam, which is responsible for the white coloration of the exhaust smoke.

In contrast, blue smoke typically indicates burning oil, which could point to issues such as worn piston rings or valve seals, whereas black smoke suggests a rich fuel mixture, pointing towards problems such as a malfunctioning fuel injector or air filter. Gray smoke can indicate a variety of conditions, including issues with transmission fluid, but it does not specifically indicate coolant leaks like white smoke does.