You should deal with water leaks in your car as soon as you can. If it remains too long in a car's interior, it will grow mold and possibly corrode electronic connectors and parts. In this article, we will look at the 6 most common sources of water leaks that occur in automobiles.

Do I actually have a leak?

The first sign of a leak into a car or truck is usually a soaked carpet. You will likely see the water pooling somewhere but in some cases, you might actually smell mold growing. In many cases, finding the source of the leak isn't exactly obvious and requires some determined detective work.

Two categories

Water that leaks into the passenger compartment of a car can be lumped into two categories: that which comes from external sources and that which comes from internal sources. In first case, the general troubleshooting technique is to allow the car to dry out completely, close all the windows and pour water on the car for a few minutes. With a little luck, when you go back inside the car, you will see a few drops of water dripping from somewhere; that will reveal where it's getting in. Internal sources can be trickier to locate but there are just a couple of sources to consider. We will discuss these below.

Inside of the Car

Leaking Heater Core - Another possible cause of wet carpet, especially in the front of the car, when it hasn't been raining, is a leak from the heater core. Car heaters circulate coolant through the dashboard area to heat the car, and if they spring a leak, coolant can drip onto the floor. Unfortunately, this is the worst kind of leak to repair because heating cores are typically very difficult to get at and thus cost a lot of money to repair. Consulting on this article was Monroeville Chrysler, a local Chrysler, Dodge, Jeep, Ram dealer located in Monroeville, PA. They also wanted to issue a warning that leaking heater cores are leaking antifreeze. Antifreeze is a highly toxic substance. Do not let family pets in your car, or children that can crawl around. It doesn't take much antifreeze ingestion to cause death.

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Clogged AC Drains - When car air conditioners cool down humid air they take the humidity out and let it drain through rubber tubes that exit under the car. If you haven't had any rain lately, and you have water leaking onto the passenger's floor, check your air conditioner drain or evaporator drain. It may be clogged or disconnected.

Outside the Car

Leaking Windshield - The number one cause of a water leak in a car is the poor installation of a windshield. If you have had a windshield replaced recently, this is a strong possibility. Unfortunately, some companies perform quick work and their windshield leak. If a professional company recently replaced the windshield, it is far less likely to leak.

Trunk Leaks - A foul, moldy smell in the trunk may result from water getting in around the trunk lid. In many cases, it is the rubber seal along the edge of the trunk lid that has become unglued so rain can leak in.

Leaking Body Seams - Body seams are the second major cause of water leaking in your car. Seams that weren't properly sealed at the factory, or seams that were broken open by an accident, can cause a mystery water leak.

Leaking Sunroof: Sunroofs are notorious for leaking. There are two mechanisms that can cause this. First, if the rubber perimeter seal is rotted or damaged, water is going to leak into your car. Sunroofs almost always have a perimeter tray with four drains installed too. Locate the drains and check that they aren't clogged with leaves and gunk.


Sometimes finding the source of a water leak inside your car is very difficult. If you have one of these mystery leaks, take it to your local dealer and have a professional mechanic take care of it before your carpets and other interior components become destroyed.