Most Likely Culprits:
* Door seals: Inspect the rubber seals around all passenger-side doors (front and rear). Look for cracks, tears, or areas where the seal is compressed or worn. Water can easily seep in through even small gaps. Try running a bead of silicone-based sealant along the seals (after cleaning them thoroughly). *However, this is a temporary solution; replacing the seals themselves is best for a permanent fix.*
* Window seals: Similar to door seals, check the seals around the passenger-side windows. Ensure they're properly seated and free of damage.
* A/C drain: The A/C system has a drain tube that typically exits under the car. If this tube is clogged, water from condensation can back up and potentially leak inside the car during heavy rain or a car wash (high-pressure water can force water through). Locate the drain tube (often near the firewall) and clear any obstructions. A small amount of compressed air or a wire hanger might do the trick.
* Sunroof drains (if equipped): Even if the sunroof isn't open, the drains can become clogged with debris. Clogged drains can lead to water buildup and leakage into the cabin. Check for these drains and clear them if necessary.
* Weatherstripping around the windshield: While less likely to only appear during a wash/heavy rain, a compromised seal around the base of the windshield can be a culprit. This is a more involved repair.
Troubleshooting Steps:
1. Visual Inspection: Thoroughly inspect the passenger-side doors, windows, and surrounding areas for any signs of water ingress. Look for water stains, rust, or dampness. Do this after it's rained heavily or after a car wash.
2. Water Test (if possible): If you can carefully recreate the conditions (a gentle hose down, focused on suspect areas), you might be able to pinpoint the leak's source more easily. Use low-pressure water to avoid further damage. Have someone inside the car to report where the water is entering.
3. Professional Inspection: If you can't locate the leak, it's best to take your Impala to a reputable mechanic or auto body shop. They have the experience and tools to diagnose and repair the leak effectively.
Important Note: Ignoring a leak can lead to more significant problems, including mold growth, rust, and electrical shorts. Addressing it promptly is crucial.
