Hey! New Guy here!
Having a concern about my 2009 Chevy Impala.
Sometimes I here waters sloshing around under my dashboard.
Before I go and pull averything out, I wanted to get a little information.

Read that there might be a clog in AC drain. I cannot find the drain. Through other sites it says the drain should come out through the firewall from the passenger side. I found the hole (I think), but do not see any tube. Can I look for it from inside the car, or from the top after I remove the filter?

Another suggestion was to change the filter. I found the steps to replace the filter. Can I purchase the filter at any auto parts store?

Someone else suggested checking the coolant.

There is no water entering my car, yet! I am trying to avoid this.
It's raining here tonight, and I am working all day Wed, Thur and Friday. I am going to try to find the tube this weekend, and will also perform the other suggestions.

This does not happen all the time. Just once in a while.

Any help would be appreciated.

Thanks

 

It's possible you have water built up from a clogged drain, but I would think the sloshing would be consistent if that were the problem. The Impala/Monte Carlo/Grand Prix are also known for allowing water to leak under the cowl at the base of the windshield. There's a fix for it that has been posted on a few different forums. Here's a link to one of those forums:

Grand Prixs Of North America • View topic - my next mod literally costs $4 from gm dealer

If you're going to change the cabin air filter you may as well take a look at the above thread and see if it applies to the problem you've been having. And yes, you can pick up the filter at an auto parts store.

 

If you recently changed the cabin air filter be careful how you mounted back the housing cover on windscreen. I have the same problem with one Ford Mondeo...when is rain i have water on the passenger side. Here you can see with picture how to change your cabin air filter to not have problems.
Cabin air filter location Chevrolet Impala, locate car filters | Car filters location, air filter, oil filter, pollen filter
I hope is useful!
Thanks!