Will the engine malfunction light come on if water enters the exhaust pipe?
2 Answers
The engine malfunction light will come on if water enters the exhaust pipe. The functions of the exhaust pipe are: To discharge the exhaust gases produced after engine combustion, reduce vibration and noise, and extend the service life of the exhaust muffler system. Precautions for exhaust pipe maintenance include: Close the choke when starting the engine cold in winter, and open the choke promptly after the engine warms up. Avoid installing windshields or decorative items in front of the engine and muffler, as they may affect heat dissipation. Do not drive for long periods at high load and low gear, as this can damage the engine and muffler. Avoid revving the engine at high speeds while stationary for extended periods. Consequences of water entering the exhaust pipe: Water entering the exhaust pipe can lead to serious consequences, such as water entering the engine. If only the exhaust pipe has water, it is essential to remove the accumulated water as soon as possible to prevent impurities in the water from clogging the three-way catalytic converter or damaging the oxygen sensor. To drain the water, simply increase the throttle to expel the water through the exhaust. Water in the exhaust pipe may cause blockage, leading to poor exhaust flow and engine stalling. In this case, the engine may not necessarily take in water; this is commonly referred to as "choking out," and there is no need to worry. Once the water drains out, the engine can be restarted. Since water is far less compressible than oil, if a certain amount of water enters the cylinder under high pressure, it can easily break the engine's connecting rod or even puncture the piston. It can also mix with the engine oil, rapidly degrading its effectiveness and ultimately causing engine seizure.
I've been repairing cars for over a decade, and water in the exhaust pipe is quite common. Simply having water in the exhaust usually won't trigger the engine warning light, since the exhaust system doesn't have sensors directly connected to the ECU. However, if water backflows from the exhaust pipe into the engine's combustion chamber, that's serious trouble—it could bend connecting rods at best or cause complete engine seizure at worst. Only when the engine starts malfunctioning will the warning light likely come on. The most dangerous scenario is attempting to restart the engine—never try to crank it again after stalling, or you'll need a complete engine overhaul. During the heavy rain season two years ago, my shop handled three flood-damaged vehicles, all ruined by owners forcing a restart.
