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adamfeather, Technician
Category: Cadillac
Satisfied Customers: 86
Experience:  Master automotive technician ,ASE master certified,associates degree in automotive technology
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I have a water leak in my cadillac sts. I cannot figure out

Customer Question

I have a water leak in my cadillac sts. I cannot figure out where it is coming from. It settles in floor in the back passenger floor board. I can get the water out and it comes right back without moving the car. What do you think?
JA: What part of the car is the leak coming from? And are you sure it's water?
Customer: I don't know when it is coming from and I am pretty sure it is water.
JA: What year is your STS?
Customer: 2006
JA: Are you fixing your STS yourself? What have you tried so far?
Customer: I have been under the dash board looking for drain pipes but have not seen any. That is why I am not sure where the water is coming from. Yes I am trying to fix it myself.
JA: Anything else you want the mechanic to know before I connect you?
Customer: no
Submitted: 11 months ago.
Category: Cadillac
Expert:  adamfeather replied 11 months ago.

Hello, my name is ***** ***** I'll be happy to assist you! I have an associates degree in automotive technology, I’m ASE certified with 15 total years in the field. Let me gather some information to help.

Sorry to hear you have a water leak!

So I fully understand can you tell if the water is leaking in from the outside when it rains or going through a carwash?

Or is it coming from the inside? Like the drain water from using the Air conditioner isn't draining and backing up into your heater box?

For instance there is a few inches of foam padding under the carpet that can be very hard to dry out once it is saturated. In the shop we usually have to partially lift the carpets up and blow fans in for hours until it is dry. My fear is that as soon as you sop up the water on the top the foam is still saturated and seems like the water just keeps getting in.

If you push on the carpet and its a puddle then its soaked into the foam pretty good.

the most common cause of a soaked floor near a door, especially in the rear is the vapor barrier inside the door panel is not sealed.

The vapor barrier is a seal of plastic separating the interior door panel from the water that runs down the window on the outside. Usually the barrier loses it's seal and allows water to leak.

Before I speculate to much let me know your thoughts so far?



Expert:  adamfeather replied 11 months ago.


I just wanted to follow up to ask if you're satisfied with your experience and whether I adequately answered your question? If not I will be glad to provide further information.

If you feel I adequately answered your question please click “accept” and rate my services if you wish. Positive feedback is what I strive for. Because I am a private expert for Just Answer I only get paid for accepted answered. Rest assured even after accepting I will always respond back ASAP to any further questions.

Thanks again and I hope I was helpful!


Customer: replied 11 months ago.
The water is definitely coming from the inside. Seems like the most water is under the front passenger seat. I'm not sure if it can be coming from the heater in the seat or not. Even if I do not use my air conditioner, the puddle still appears.
Expert:  adamfeather replied 11 months ago.

Ok good. If your sure it's coming from the inside then it can only be a few things. The only things that can produce water in the interior is the water produced by the air conditioning, note the ac will still be on when your using defrost to help dehumidify the air and if the vehicle has automatic climate control it may be on even when heat is used to help dehumidify the air. The heater core has coolant that may leak but it wouldn't be clear like water and should smell similar to maple syrup or pancakes if it was leaking inside. The other possibility is if you have a sunroof the drain pipe may be disconnected inside the pillar somewhere and running down. But this would only be during rainfall.

I'm also still concerned the foam is saturated making the puddle never really go away. You may have to partially remove the carpet to see if you can see where the trail of water originates. Let me know your thoughts and how else I might be able to help. I likely won't be back until this evening. Sorry for any delay!



Expert:  adamfeather replied 11 months ago.
Here is a picture of the evaporator drain tube. It shows it in the driver side next to the gas pedal. You should be able to peel the carpet back far enough to see it and pull it out to inspect for blockage. It seems to be a common issue but tough without being there to see it. Let me know what else may help.