Noisy When Wet

Hi Guys-

I have a 2003 Pontiac Vibe GT - same car as a Toyota Matrix. It’s a 6 speed standard. When driving in heavy rain where the street is flooded by an inch or more of water the car makes a noise like the bottom is going to drop out. It comes from underneath and makes a womp-a-womp-a-wompa sound that shakes the car. I initially thought it was one of the plastic panels below the car that was loose and catching water that would make it slap back and forth. But my mechanic couldn’t find any loose panels. Someone told me they had something similar with a Dodge Caravan and it was the timing belt getting wet - only I have a timing chain. I can’t tell if it is related to the revs of the engine - it might be. It’s such a scary sound I take my foot off the gas and it does seem to go away as the car slows. Seems like keeping under 30mph and out of the puddles helps. This is only in heavy rain, street flooded conditions. Help!


Instead of, “timing” belt, I suspect that the other person meant serpentine belt. Timing belts are cogged in such a way that they don’t normally slip, and if they do, they don’t self-correct afterwards–with disastrous results for many engines.

A serpentine belt can definitely be affected by a lot of rain, but…I can’t connect a wompa-wompa sound with a belt.

I would be more likely to suspect a problem with a loose exhaust system (including the exhaust manifold), based on the description.

Thx - will have my mechanic inspect exhaust system.

& Make sure all of the tires are in good condition and properly inflated. And CV boots are ok.