During peak summertime, a sunroof can make all the difference to family outings and long commutes, helping to keep occupants cool while allowing fresh air and sunshine to flood in.

But when cooler weather arrives sunroofs get closed, and have to contend with more regular precipitation - which is when a leak can become apparent.

If you do spot a leak, it's important to fix it and minimise any damage - to the cosmetic look, or even to the electric window components or infotainment system. In doing so you'll help protect the resale value of your vehicle.

 

Signs your sunroof is leaking

If the leak is serious, you'll be able to spot water ingress easily. But a minor leak might show up as:

  • Barely noticeable trickles or drips around the sunroof
  • Water-stained headliner
  • Musty smell in the cabin
  • Mould spores on seats and carpet
  • Water marks on seats and carpet

 

The two most common culprits:
  • Block drainage holes
  • A damaged seal

 

Block drainage holes

This is probably the most likely of the two issues. Many people attempt to clear blocked drainage holes with a wire, a coat hanger, or by trying to force out debris with an aerosol. However, these approaches could easily damage the rubber drainage tubes which run down the car’s front "A" pillars. Damaging these tubes may result in an even bigger repair job.

 

The vacuum approach

For this technique you'll need a vacuum, a trap adapter that forces the air through a small hole, a vinyl hose and a hose plug.

Attach the trap adaptor to the end of the vacuum hose, then using the hose plug attach this to the vinyl hose. This set-up should be all you need to clear the dirt and debris from the tubes.

Check the tube has been cleared by pouring a little water down the hole. if it has been successfully cleared, the water should disappear relatively swiftly.

 

Clear the hole with a section of thin, bendy wire

Use a very pliable length of wire - such as a bicycle brake cable - and carefully insert it into the drainage hole. Wiggle the wire to clear the debris, taking extra care not to damage the internal tube.

Once you think the tube is clear, introduce some water to the hole and see if it clears promptly.

 

Trombone cleaners

Trombone cleaners - sections of wire with small brush heads - are also effective for cleaning such drainage holes without causing damage, and cost as little as £7 online.

 

How to fix a leaking seal

If your drainage holes are clear, the seal is almost certainly the culprit. You'll probably notice droplets around the seal if this is the case.

Examine the seal for cracks - ideally using a magnifying glass. Look for water marks and mould.

Having located an area of damage, find some black liquid electrical tape and let it dry. Check to see if the fix has worked by pouring a little water over the affected area.

 

No luck?

If the above steps do not work, consider taking your car to a sunroof repair specialist. It's probably not a good idea to take apart the sunroof system yourself unless you have substantial experience in the area.

 

Good maintenance

Although few motorists do so, it's a good idea to vacuum your sunroof's drainage holes once or twice a year - especially at the end of summer when rain is more likely. Lubricating your tracks and bearings with silicone grease will also help prevent damage to your sunroof's opening mechanism.