For years, the car leaks under the passenger side dash into the carpet when it rains. We had asked the Buick dealer to look into it & were told it would be impossible to locate the leak. Now, several years later we have obvious mildew in the carpets. Car has low mileage, but I want to keep it several more years but cant tolerate the mildew. I dont want to replace carpets w/o being able to fix the leak. Was the dealer just lazy or is it really impossible to locate a body leak like that.
I suspect they should be able to find the leak. Either a windshield needs to be reseated, a drain hose is pluged, a crack or lack of sealer in the couling, etc. If you can show where it ends up, they should be able to trace it back-may not be easy but what is? The body service manuals have procedures for finding leaks.
I suppose the dealer probably checked it, but…
The cabin air filter is on the firewall, just above the passenger foot well. You get to it by removing the passenger side wiper and then the windshield cowling at the base of the windshield. There is a rubber window gasket that acts as a water diverter at the bottom edge of the windshield and directly above the cabin air filter. If it is not seated correctly, water will get into the filter, then it will fill up the heater/AC blower. After the blower housing is filled, the water leaks onto the floor. It’s a long shot, but it might be your problem.