Why is my car wet inside?

If you’ve noticed the interior of your vehicle getting inexplicably damp, no doubt you’ll be wondering what the culprit is. We’re all familiar with wet on the outside of our car, but what about inside? 

To help you solve this puzzle, we’ve put together this article exploring the most common causes of moisture in a car and how to address them. 

6 signs of car moisture

If you’ve spotted any of the following telltale signs, you could have a car moisture problem that needs looking at. 

• Damp floors: Car upholstery is generally dark, so you might need to have a feel around to identify any wet patches. Other times, dampness can be more obvious and have a clear visual tell, like water droplets or darker patches. 
• Discolouration: If there’s a leak, this could lead to discolouration of interiors as dirt accumulates inside. 
• Misting windows: When temperatures change and shift, any excess moisture within a car can lead to condensation gathering on the windows. If this is a repeated problem, it may indicate a leak or faulty weatherstripping. 
• Musty smell: Don’t ignore a musty, earthy or stale scent, as it could be a warning sign that mould is starting to develop. 
• Electrical faults: In severe cases, moisture penetration problems in a vehicle can cause electrical faults and damage to components.
• Corrosion and rust: If the issue has been left to linger, eventually rust can form and parts of the car can start to corrode. 
• Sloshing noises: When water is trapped in certain spaces, it may make a sloshing sound as the vehicle moves.

Catching these signs and taking action is essential to stop the damp problem from worsening, which can potentially cause further interior damage to your vehicle.

Common causes of car moisture

Now you know what to look for, you’ll want an explanation. Here are the most common causes of moisture build-up inside a vehicle.

• Obvious but overlooked: First, establish if windows and sunroofs have been left open for any length of time, or if someone using the car has driven through deep water recently. 
• Damaged seals: Door, window and sunroof seals are there to keep moisture out and the car dry, so if weatherstripping is damaged, shrunken or worn in any way, this could be the reason for the excessive moisture. Regularly conditioning these seals to keep them flexible is a good preventative tip to remember. 
• Clogged sunroof drains: Most sunroofs have small holes in them to allow for effective drainage of roof rain to the ground. If these holes or passages become clogged with leaves or debris, they can struggle to do their job. Check these and unclog any obstructions you find. 
• Missing or damaged trim pieces: If there are any absent or defective components of the car trim, such as screws or panels, then water can leak through these vulnerable areas and into the interiors of your vehicle. 
• Heat or AC problems: If the heating or air conditioning system is damaged, this can cause coolant to leak into the footwells, which may also have a distinctive sweet smell. 

The cause of your car’s moisture may not be any of the above, which is why it’s important to get a professional on the case if you’re unsure. 

How to fix interior car moisture

First, you need to clear away the moisture with a cloth and a vacuum that has a water-suction nozzle or function. Then you need to ventilate the car by leaving doors and windows open for a period of time. If you have a dehumidifier you may want to run it inside the car to help speed up the drying process. 

Once the dry-up is complete, check for all of the above potential causes suggested in the previous section, identifying the source and making DIY corrections if that’s feasible for you. Only make fixes that you can comfortably accomplish, or else you risk making things worse. 

The surest way to get moisture problems fixed is with the help of a professional. Damaged seals and trim often need the skill of a car expert who can identify the vulnerable areas and administer a swift solution. Likewise, any issues with heating and cooling systems need expert input. 

Whatever your car problem – from a slow puncture or unbalanced wheels to diagnostic issues, get a resolution from Mr Tyre, the leading chain of autocentres for Central England. Established in 1971, we’ve helped thousands of motorists get their cars back in roadworthy condition, and we’ll be happy to help you, too.