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Water leaks in a car are more than a nuisance; they can cause damage to the vehicle itself. Most of the time, water causes mildew and mold to form on and under carpets and cause rust to the floor pan and other metal components. If water leaks into the electrical system, it can cause serious short-circuits and other damage that is difficult to find and repair. Electrical issues can be very costly to repair and diagnose.

Unfortunately, water leaks can be very hard to find. Often, the place where the water shows up inside of the car is not close to the place where the water is entering from. Sometimes, the two locations can be a couple of feet apart. Water can enter the vehicle and travel through a channel in the body or interior trim before reaching the place where it shows up.

This guide discusses the major types of water leaks and how to repair them. Some of these repairs can be done by the owner, while others require the assistance of a professional.

First Step: Diagnosis

As with any sort of troubleshooting, a lot of the process for finding a leak is mind set. It is necessary to start by looking at where the leak is and when it shows up. Determine whether the water is only there when it rains and whether it only occurs if it rains hard or if light rain can cause leakage as well. Figure out if the car has to be moving or making a turn for it to leak, as well as when the car started leaking.

Water leaks typically leave some sort of telltale marks. Wet carpeting or upholstery is an obvious one but not all leaks are that obvious. Many leaks cause water stains which are mineral deposits left behind by the water when it evaporates. Another key indicator is rust on the inside of the vehicle. Rust will not form unless the inside of the vehicle has been getting wet.

The more information one has about when the car is leaking and under what conditions it is leaking, the easier it is to determine exactly what is causing the leak.

Common Causes of Leaks

Many different factors can cause a leak in a car. Some of them involve normal wear and tear of the vehicle, while others are caused by poor collision repairs, a poorly installed aftermarket windshield or the addition of aftermarket accessories.

Windshield

If the car’s windshield was just recently replaced, chances are that it is the culprit. A proper windshield replacement requires complete removal and replacement of all of the old urethane.

If not enough of the urethane is used or the old urethane was not fully removed, the windshield may not seal properly. Since the urethane takes some time to dry, the vehicle should not be driven for several hours after the new windshield is installed. If it is driven, it can cause the seal to fail or worse cause your air bags not to function properly in case of an accident.

Never use silicone to seal a leaky windshield, as this will prevent the correct sealant from adhering properly, should the windshield be replaced in the future.

Weather Strips

The second most likely area for a car to leak is at the door seals especially in older cars. While the style of door seals can vary considerably, they are all foam rubber, which has a sealed surface. When the door is closed, this seal is compressed between the door and the door frame, making a secure seal.

Any rubber part is affected by age and heat accelerates this process. Thus, in hot climates, the deterioration of door seals is quicker than in cooler climates. As the rubber ages, it dries, shrinks and can crack. Additionally, it is not uncommon for door seals to become torn when putting large objects into the car.

Another problem that can affect door sealing is accidents. Some accidents cause the vehicle’s body and frame to warp. Body shops try to make the car look like new again but in doing so, they may not deal with this warping. Instead of straightening parts (which may be impossible), they may shim them to look right. However, this can leave a gap in the door seal that is not visible.

Door seals can be replaced. It is essential that the seal be properly aligned.

Body Seams

Any place where two body panels come together is a prime place for leaks. When these seams are low down on the vehicle, they usually are not a cause for concern. However, when they are on the roof or near the rear trunk, they can cause major leaks. When these seams leak, the entry point for the water can be as far as a couple of feet away from the where you notice the water.

Body seams can leak if they were not properly sealed at the factory. They can also open up from an accident or hitting potholes due to colder temperatures thus breaking their original seal. This would typically be a small leak that is very hard to find. The biggest problem with finding these leaks, besides the fact that the water exits at a different place from where it enters, is that the sealant in the seam makes it look like there should not be a leak.

This type of leak requires that the old sealant be removed and new sealant be put in its place. Silicone sealant should not be used; as it will prevent paint from sticking, it can also cause rust as silicone contains acetic acid. There is a special body seam sealer available in caulking tubes that is designed specifically for this purpose.

Sunroofs

Sunroofs are a common area for leaks. If the seal around the sunroof becomes damaged, water will enter, especially when driving through rain or car washes. OEM sunroofs are designed and manufactured with a “pan” all the way around the perimeter of the sunroof to catch any water that tries to enter. There are drain tubes in the four corners of this pan that allow excess water to drain out of the vehicle usually behind the dash or out by the wheel wells.

It is possible for these tubes to become disconnected or blocked with debris. Should a tube become disconnected or blocked, it is fairly easy to repair it. Blockage can be cleared out by shoving a piece of weed eater line through it. Care must be taken to avoid puncturing the tubing when doing so. Tubes that have slipped off the fitting can be reinstalled. If this is the case, be sure to attach the tube with a small hose clamp to help prevent it from falling off again.

Accessories

If the leak begins shortly after the installation of an aftermarket accessory on the exterior of the vehicle, there is a high probability that the installation caused the leak. Aftermarket sunroofs, moonroofs and luggage racks all require drilling holes in the roof of the vehicle. If these holes are not properly sealed, water can seep in through them.

Sunroofs and moonroofs should come with rubber gaskets to put under their flange during installation. The operable part should have an adequate rubber seal to seal it against the frame. However, some lower-cost units may not have sufficiently well designed seals. In these cases, the addition of self-adhesive foam weather stripping may help.

Roof racks do not always come with any sort of rubber seal to go under them. However, the mounting holes must be sealed. If there is no seal provided, they can be sealed with caulking. A pure silicone caulk should not be used, but a silicone mix can be. An alternative way to seal them is to cut a rubber seal out of sheet rubber or an old inner tube.

Aftermarket remote start or wiring could also be an issue if not done properly. Sometimes holes are drilled to run wires and the hole is not properly sealed or a drip loop not installed in the wire.

Corrosion

Some models of cars have a tendency to rust above the windshield and back window. Even if the roof is not visibly rusted all the way through, it is possible that it has rusted enough to allow water to seep through.

To accomodate this type of repair, the glass will have to be removed. It is necessary to remove as much of the rust as possible and then stabilize the remaining metal so that it will not rust. A phosphating solution is good for stabilizing rusted steel. Once that is done, body filler can be used to fill in the rust and skim over the area. The area must then be sanded smooth and repainted. This is a job for a body repair professional.

AC Leaks

It is possible that what appears to be a leak is not a leak at all. The air conditioning evaporator is located under the dashboard of the car, either in the middle or on the passenger side. Moisture typically condensates on the outside of the evaporator whenever the air conditioner is in use. If the drain tube comes loose or is blocked by debris, this condensation will drip on the inside of the vehicle floor causing a wet floor.

This is a simple problem to repair, requiring only the cleaning out and reattachment of the drain hose. To clean any debris out of the hose, run a piece of weed eater line through it.

Another possible cause of leaking inside the vehicle, besides water, is coolant from the car’s engine. The air conditioning evaporator is part of the vehicle’s heater (it looks like a small car radiator). This uses engine coolant to bring heat from the engine into the vehicle. Just as a radiator can have a hole in it, this coil can as well. It will cause coolant, which is sweet smelling and slightly sticky to come into the vehicle, under the dashboard.

Repairing a heating core requires removing it from the vehicle and replacing it. Depending on the design of the vehicle, it may be necessary to remove the dashboard or part of the dashboard to access the heater core. This is a time consuming and expensive repair and should be performed by your local service repair professional.

Conclusion

Troubleshooting water leaks in a vehicle can be challenging, as the entry point for the water may not be where the water is appearing on the inside of the vehicle. It may be necessary to remove interior trim panels to gain access to the vehicle’s body and see where the leak is originating from.

At LEAKPRO® we know the issues and have the training, tools, products to repair the leak(s) in a fast and efficient manner. Our highly skilled technicians have the means to repair the water leak and remediate it’s aftermath of mold, mildew and wet carpets. The OEM’s trust LEAKPRO® so does your dealership, you should too. Give us a call today.

What People Are Saying About Us

I had a great experience working with Mike and his team at LEAKPRO. They provided great quality work and excellent customer service, for a reasonable price. Mike and his team are very well-versed in this specialized area of car maintenance and they stand behind their work. Highly recommended!

Calvin J, SurreyBC

After having my 2016 Buick Lucerne repaired unsuccessfully 6 times by my GM dealer I heard of LEAKPRO. I called LEAKPRO, John came out and had my car fixed in 1 hour. The front sunroof drain tubes from the factory were actually trapped at the dashboard. John installed two new drains and I have never had another leak!

D. Barlow OttawaOntario

My LEAKPRO representative Jesse did a great job fixing an intermittent water leak that would wet the back seat of my new truck. Jesse quickly pinpointed the problem and fixed it. No leaks now! Great service!

K. Peters VancouverBC

I had an ongoing issue with a leak in my 2017 F150 from under the left side dash. My Ford dealer could not pinpoint it after 4 times. The dealer finally called in LEAKPRO and the leak was resolved within a couple of hours. We have had a lot of rain, and no more leaks! LEAKPRO knows what they are doing!

D. Wiley HamiltonOntario

I had a musty smell in my used car I had recently purchased. MY dealer called in LEAKPRO, and it was determined that the smell was due to a water leak. LEAKPRO fixed the leak, replaced all l the under pad and disinfected the flooring. My car smells great and no more leaks!

A. Stayrer TorontoOntario

I had a big water leak in my brand new truck on the right side. I was so upset, my carpet was soaked! My Service Advisor said not to worry we use LEAKPRO. I received my vehicle back at the end of the day as promised, I felt the carpet it was dry! I lifted the carpet to check underneath and it was dry, all new under pad and fresh smelling. My service advisor informed me it was a skip in the sealer from the factory. I am so happy I had to write!

B. Slater WindsorOntario

I had a wind noise on my brand new Charger that my dealer after two attempts could not figure out, it was driving me crazy. I went to another dealer and they said no worries we bring in an outside specialty company. I arrived at the dealership for my appointment as I wanted to drive my car with the technician so he could hear what I was experiencing. Steve from LEAKPRO said he knew what the issue was and had it fixed within an hour!!! THANK YOU LEAKPRO!

J. Stanwich KitchenerOntario
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