What happens if the engine exhaust pipe is not connected?

[ReidMarie]

Regarding the effects of not connecting the engine exhaust pipe, the related introduction is as follows: 1. Emission obstruction; Under certain specific conditions, the engine's exhaust gas is introduced into the intake pipe to mix and participate in combustion. Since the exhaust gas cannot burn, it reduces the combustion speed and temperature in the cylinder, thus failing to achieve the goal of improving emissions. 2. Combustion contamination: The exhaust gas inside the engine crankcase is introduced into the intake pipe to participate in combustion. 3. Environmental pollution: Not connecting the pipe affects the environment, as some unburned gases are directly discharged into the atmosphere, which may also cause noise, abnormal engine operation, and failure to meet emission standards.

[OJustin]

I've personally seen cars with improperly connected exhaust pipes where the high-pressure exhaust gases in the crankcase had nowhere to go, causing pressure to skyrocket. This easily forces oil out through the gaps in the oil seals, leading to leaks everywhere. The scariest part is that leaked oil dripping onto the hot exhaust manifold increases the risk of smoke or even fire. A friend of mine experienced this while driving—oil spilled everywhere and nearly caused an accident. Over time, the crankcase fills with carbon deposits, accelerating wear on piston rings and bearings, drastically reducing engine life. If you smell burning oil or notice oil stains under your car while driving, stop immediately to check the pipe connections. Safety is no small matter—don't risk big trouble to save small money.

[StReese]

After modifying the engine that time, I forgot to properly reconnect the crankcase vent hose before the test drive. The engine ran rough with noticeable acceleration lag, and fuel consumption surged by at least 15%. The cabin was filled with a pungent oil smell that made me nauseous. Later I discovered leaked oil had soiled the engine exterior, which was a pain to clean. Simply put, an unconnected hose directly vents crankcase gases, causing unstable engine temperatures. Beyond performance degradation, it pollutes cabin air and harms health. Now I've developed a habit of visually checking the vent hose position during every maintenance to avoid repeating this ordeal.

[PaisleyAnn]

Having run an auto repair shop for years, I remind car owners that disconnecting the crankcase vent hose harms the environment: Unprocessed crankcase emissions released directly into the atmosphere increase hydrocarbon and particulate matter emissions, violating environmental regulations. Some shops forget to reinstall it during inspections, causing customers to fail annual emissions tests and face fines. The exhaust contains oil mist, contaminating soil and water sources. Worse, external dust can enter the engine, jamming valves and leading to costly component damage. Don't just cut corners—regularly clean the ventilation system to protect our blue skies, which also brings long-term benefits.