VW Touareg Fogging Up? This One Had a Hidden Leak That Could’ve Gotten Ugly

By Northcap – Roadside Rescue Mechanic

It’s not often I get a call-out for foggy windows, but this one popped up on the system as a VW Touareg with interior misting. The member reported a weird build-up of condensation after rain—more than just the usual fog. The kind where the windows looked like they were dripping on the inside. No other symptoms, but he wanted a mechanic’s opinion before things got worse.

Smart move.

The Setup

When I arrived, the Touareg was parked on a sloped driveway out front. Not my favourite place to work—especially when you’re crawling around trim and wiring. So I asked the member if I could move the car to a flat area around the back of his property. He had a solid level patch of hardcore—ideal for both my van and the job at hand.

Before I hopped in, I asked the usual questions.

He told me he’d only owned the car a couple of months. First noticed the fogging issue about a month ago, and it seemed to be getting worse. After rain, the windows were misting heavily on the inside—not just a little foggy, but dripping. He had checked under the mats but said everything felt dry. I asked about coolant levels and heater performance—both were fine. So at first glance, a heater core leak seemed unlikely.

I also considered a blocked A/C evaporator drain, which can cause moisture buildup if condensation has nowhere to go. Still on the list, but something didn’t quite add up.

First Clue: Water Where It Shouldn’t Be

I started the Touareg and reversed it around the back. That’s when I heard it—a faint sloshing sound, like water trapped somewhere. Sounded like it was coming from the passenger side front.

That was my first real clue.

Sunroof Inspection

I opened the sunroof and checked the tray and seals. No debris inside—looked pretty clean—but I noticed green staining around the drain holes. That suggested there had definitely been water movement, and potentially a slow leak.

I asked the member if he’d used the sunroof. “No, not yet,” he said, “but I tested it before I bought the car, and it worked fine.”

The property was set in a wooded mountain area, so pine needles and debris clogging a drain was a possibility. But since the member hadn’t used the sunroof, I didn’t expect a full-on blockage. Still, it was worth checking further.

Finding the Leak

The carpets felt dry to the touch, just like the member said. But I’ve been here before—carpet underlay can hold water like a sponge, and by the time it seeps through, the damage is usually already done.

I removed the kick panel on the passenger side and slipped a blue paper towel under the carpet edge.

Pulled it out soaked. Properly wet.

Okay—leak confirmed. Now to find the source.

Jackpot

Since the sloshing sound came from the passenger side, I removed the windscreen A-pillar trim to inspect the sunroof drain tube. You can’t see much from inside the sunroof opening—it’s all hidden. But once I got the trim off…

Splash. Water poured out.

The drain hose wasn’t even connected. Just hanging there.

Best I could tell, this wasn’t a recent DIY job. The hose looked like it had never been fitted properly at the factory. These tubes are snug-fitting and tough—they don’t fall off on their own. Unless someone had been in there doing bodywork, this was likely a rare factory fault.

I showed the member before I connected it.

The Aftermath

With the leak stopped, the next issue was the interior water damage. The member asked if he could just run a dehumidifier inside the car.

“Sure,” I said, “it’ll help. But me? I’d pull the interior apart.”

That underlay holds a lot of moisture, and modern vehicles hide a mountain of control modules under there. These systems aren’t waterproof—they’re not meant to be wet. Leave them soaked, and you’re asking for trouble: warning lights, electrical faults, mystery issues down the line.

Still, it was his call. I gave the advice, showed him where to check, and left him to decide.

Takeaway for VW (and Sunroof) Owners

• If your car mists heavily after rain, especially with dripping windows, don’t ignore it.
• A dry-feeling carpet doesn’t mean the underlay’s dry—check deeper.
• Sunroof drains can clog—or worse, disconnect completely.
• Listen for sloshing—it’s often your only early clue.
• If you find a leak, don’t stop at fixing it—inspect the interior for hidden water damage.

Sometimes it’s the simplest things that cause the biggest headaches. A hose not clipped in. A little water in the wrong place. And if you don’t catch it early, it’ll cost you more than just foggy windows.

Stay dry out there.

– Northcap