* Sunroof Drain Tubes: Clogged sunroof drain tubes are a very common cause of interior leaks. Water backs up and overflows, often finding its way to the rear floorboard.
* Rear Window Seal: A leak around the rear window seal is another frequent problem. Over time, the seal can degrade, crack, or become improperly seated, allowing water to seep inside.
* Tail Light Assemblies: Cracks or improperly sealed tail light assemblies can let water into the car.
* Weatherstripping: Worn or damaged weatherstripping around doors, particularly the rear doors, can allow water to enter and run towards the back.
* Trunk Seal: Similar to the rear window and doors, a faulty trunk seal can allow water entry, especially if the trunk is frequently exposed to rain or car washes.
* AC Condenser Drain Line: While less likely to directly affect the rear floorboard, a clogged AC condenser drain line can overflow and potentially contribute to a leak depending on the car's drainage system.
* Holes in the body: Less common, but possible, are rust holes or damage to the body that allows water intrusion.
To diagnose the leak:
1. Visual Inspection: Carefully examine the areas listed above, looking for any signs of water damage, rust, cracks, or loose seals. Pay close attention after a rain shower or deliberately hose down the suspect areas while observing the interior.
2. Water Test: If you can't visually identify the source, carefully pour water onto suspect areas (sunroof, windows, etc.) to simulate rain and see where the water enters. Have a helper inside watching for leaks.
3. Professional Inspection: If you can't find the source after a thorough inspection, it's best to take your Malibu to a qualified mechanic or body shop for a professional diagnosis and repair. They have tools and experience to pinpoint leaks that are difficult to identify.
Remember safety first when conducting any water tests. Don't use excessive amounts of water and avoid getting electrical components wet.
