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Find And Fix Car Water Leaks

Inside VW Beetle with no carpet and tatty interior
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Find And Fix Car Water Leaks

Water getting inside your classic car or campervan is a surefire way to take the joy out of ownership. Not only does dampness ruin an otherwise smart interior, but if left for too long will inadvertently rot out floors and sills. On top, there is the annoyance of internal condensation, plus moisture and car electrics aren't friends; if circuit boards and crucial electrical connections corrode, you'll be faced with all manner of spurious faults which can be tricky to trace.

Stop water leaks before they happen

As always, prevention is better than cure so do try to stop water ingress before it happens. Even if your car is dry, take a closer look at any grommets or blanking plugs you may have fitted, as these may encourage water to slip inside when the weather turns. If the situation is more urgent and puddles have arrived already you can still do something about it. Watch out for rust bubbles like this around Mk2 Golf rear screen seal, and look for signs of water drops on interior metalwork as they can often lead to the source of your problem. 

Fixing door seal leaks

There's a good chance water could be getting in via an aged or damaged body seal. As rubber seals age, they dry out and crack creating gaps in their sealing surface that water can exploit. If this is the case, carefully remove the old rubber and replace it. Your door rubbers (or another aperture seal) will either be pressed into place, or secured with glue (like Evo stick) and are available for virtually every model. A good tip here is to warm the new rubber first with a hairdryer to make it more flexible and easier to fit. Oh, and if the water is still getting in check the fit of the door itself and adjust the latch mechanism and hinge alignment if necessary. 

Water appearing at the bottom of the door might not be due to a failure in the perimeter seal. Almost all vehicles have windows that go up and down, and the 'scraper seals' that these run against shrink in the sun and also crack with age. Whilst they are designed with this in mind, they also rely on the fitment of a plastic membrane inside the car door to stop any water from going beyond that point. A missing or damaged membrane can let the water in and this might show up as damp or deformed door card bottoms, or water droplets along the tops of the sill carpet. 

To complete the job, make sure the door drain holes are clear of any debris or waxoyl to allow water to escape outside as the manufacturer intended. 

Why do my car window seals leak?

As soon as rubber ages and begins to perish there's a risk of it letting in water, and the bottom corners of the windscreen rubbers are where you will probably notice it first. It is also possible that your window rubbers and seals could leak if they don't fit the profile of the bodywork properly. This might be because they are of lesser quality, have been fitted incorrectly or the metal aperture is now the wrong shape following a poorly executed repair. If this is the case, have it done properly and fit a top-quality windscreen rubber to create the perfect seal.

Do also watch out for rust and holes hidden underneath a rubber seal which could lead to you needing a specific repair panel. Whilst it may be an inconvenience to fix the issue now, your efforts elsewhere will be quickly undone if moisture still has easy access to your interior. 

Keep all drain holes clear

Lots of cars have what's called a plenum chamber which sits between the windscreen and the engine compartment, typically where the bonnet hinges are and quite often where the battery is located. The problem here is leaf debris collects in the bottom and, if the drain holes get blocked, water can spill into the car's cabin (wet leaves also encourage rust too). The solution is simple; keep the chamber squeaky clean and the drains clear so the water can get out. Be aware of perished or split grommets that carry wiring through to the cabin. If these have been compromised you'll have a footwell water feature in no time.

Why is my carpet wet?

Wondered why your Porsche or VW carpets are always wet? As the lowest point in your car, water will naturally run down and gather here, regardless of where it is coming from. Remember, your car doesn't remain still, so each time you negotiate a roundabout or summit a steep slope you are adjusting the angles and helping the water flow to the floor pan. 

What is great for cabin comfort isn't so great for water leak hunting. Thick sound deadening and underlay will absorb a lot of moisture under the carpet which will keep an issue hidden for quite some time before you discover it. The 'sponge-like' property of underlay also encourages the rust to come out and play - so time is of the essence. 

If you're late to the party it could be that rust has eaten away at the metal beneath and inconveniently created a hole, allowing dampness to attack from above and below. Lift the carpets to see if this is the case and pull all that soggy sound deadening out immediately, as not only is it wet, it will smell terrible too. 

Use your detective skills to narrow down the reason for wet carpets. Is it only happening on one side, just in the front, or the back as well? Is there a route for water to pass between these areas, or can you take your discovery as the real scene of the crime?

Why is my car boot wet?

In a similar way to the cabin carpet, the boot and the spare wheel well will collect and hold water leaks from a number of places that are higher up. There are a few places to check but first start by removing everything, including the carpet and spare wheel tools.

Run your hands along the metalwork of the boot floor and inner arches/pillars and work upwards feeling for dampness, but also dryness too. If you go from wet to dry, you can assume that point is higher than the water leak. 

Popular places for the water to get in are on the tailgate itself, including high-level brake lights, wiper motors, and washer jets. Number plate lamps and boot handle plinths are also potential water sources, and then on the vehicle body itself the tail lamps. 

The tail light to body seals are a common failure point and rear lamp units often trap moisture due to their complicated shapes. If you are unable to source the correct replacement seals, you could look to fix the issue with silicone sealant, but ensure the area is nice and clean and dry first or it won't stick. 

Why does my car sunroof leak?

Cutting a big hole in the top of a car to fit a sunroof is certainly inviting water trouble, and it all depends on how well it has been done, as to how dry you will remain! Factory-fitted sunroofs (metal or glass) tend to be fairly well-considered and will have drain holes in place to direct any sneaky water drops that may get past the sunroof seal

A retrofitted sunroof, supplied either by a dealer or a specialist in the period, may be less well supported for spares and could leave you with a conundrum: seal it shut for good or persevere fighting the leaks. If you chose the latter you could find the rubber seal between the glass and the frame has lost its spring. Sliding something under this can help to boost it back up again in the absence of a brand-new replacement. 

Fabric sunroofs, much like cabriolet roofs below, have a few extra issues of their own, read on...

Dealing with cabriolet roof leaks

There is a good reason why Cabriolet models are cheaper to purchase in the winter - they have a tendency to let water in! Not something you think about on a hot summer's day when you hand over your money, slip on your shades and drive down the road with a huge smile across your face.

It's fairly obvious in hindsight, that if you have a classic car 'without a proper roof' and plan to use it all year round, there will be some damp patches after a downpour. Older models like the Beetle Cabriolet and Mk1 Golf cabriolet are likely to be the wettest of the lot. Newer cabriolet models such as the 986 Boxster, Mk3 Golf, and later Porsche 911 models will benefit from more complex sealing arrangements. 

Once more you have to become a detective to solve Cabriolet water leaks. If the tops of your seats are getting wet, you can rule out anything below that - boot seal, missing grommets in the engine bay, etc. If however, it is the carpet that is drenched, it could be anything above that.

Take a few minutes to inspect the condition of the roof and the rubber seals from the outside. If you were a water drop, where would you try and sneak in? Are there any rips or tears in the hood material? Is it clear that some rubber seals don't quite meet up correctly?

If you have a garden hose and a second pair of hands available, get inside the car and ask your friend or partner to slowly rinse the top of the roof and work their way down each side. Simulating a rain shower, you are looking and feeling for water getting inside, whilst it is happening. If the problem is wet carpets, strip these out first so you can see the path that the water is running from. This diagnosis method will save you a whole lot of time and towels in the long run, and don't rule anything out - water will travel through components to get in if it has to. 

Find new Golf Cabriolet and Beetle Cabriolet roof seals online here.

I've had my fair share of damp cars, and know it isn't nice, especially in the colder months. Hopefully, this guide will give you the confidence and guidance to address your water ingress issues now help and prevent future leak-related problems too. Best of luck!

Andy 

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