I have a 2001 Monte Carlo LS with just over 18K original miles. After a heavy rain, it is not uncommon to find a small puddle of water on both the left and right rear floorboards. Despite this, there is no evidence of moisture intrusion at the door weatherstripping or the door sills. The puddles are on top of the floor mats and the carpeting remains completely dry. The front floorboards are dry. All seating is dry. All glass surfaces are dry. The headliner is dry. I can find no trace of moisture anywhere else in the vehicle. Just a small puddle, on top of the mats, on both the left and right rear floorboards. Where this water is entering is an absolute mystery to me. It only appears after a moderately heavy rain. Has anyone here ever experienced this particular problem? Thanks in advance for any feedback.

 

I would check a few things:

!. Clogged disconnected and/or leaking sunroof drain hoses. Drain openings are at each corner of the sunroof.
*Freezing can cause ice to form in the hoses causing blockage and/or disconnection.

2.Leaking windshield seal. This might show up as condensation on the top inside of the windshield.

Hope this helps.
Keep us posted

 

I had that same problem, and I live way up north so it would rain and then it would freeze. So I'd have a block of ice for my floor mats. I found out the weather stripping for my sunroof wasn't sealed all the way. So I resealed it and it went away.

 

This car doesn't have a sunroof.

 

Well next thing I'd suggest , would be to sit in your car when it's raining and wait to see where the water is coming from.

 

I think that may be the only thing I haven't tried.

 

Hope you find it 👍🏻

 

Hope you find it!

 

here an idea, look at the rubber seal around rear window and side windows just an idea

 

My money is on door seals even though they look right.


Get someone with a garden hose or go to the manual spray car wash with you inside and have someone spray the car.