How to Repair Your Car's Sunroof

salesman explaining sunroof function on new car
Sunroofs are a great option on many cars, but only as long as they work.

The sunroof (or moonroof) of your car is a prime place for leaks to appear. However, before you mar your paint with duct tape or gunk up the whole works with silicone sealer, it's important to understand how the sunroof works. Then, we'll discuss several DIY ways to keep the rain outside your car, without sacrificing the convenience and comfort a sunroof provides. 

How Sunroofs Work

Vehicles with sunroofs allow for extra light and ventilation on nice days. Or are they called moonroofs? The first “sunroof," a retractable metal panel in the roof of a classic Nash, appeared in 1937. A little over three decades later, Lincoln introduced the “moonroof,” which was made of glass instead of metal. This meant that, even when closed, the ’73 Continental Mark IV’s moonroof allowed a little light into the cabin.

Today, though, it doesn’t seem like there are any rules regarding what they should be called. “Click” and “Clack” of Car Talk fame say sunroofs are metal and moonroofs are glass, but the industry still hasn’t reached a consensus. All glass panels in the roof, whether fixed, retracting, or tilting, are interchangeably referred to as moonroofs or sunroofs, as are vehicles with retractable textile panels. For the sake of clarity, we'll use the term sunroof from now on.

Most sunroofs fall into two categories: internal and external. Internal sunroofs fit between the metal skin of the roof and the headliner, retracting into a hidden pocket. External sunroofs, which are less common than internal sunroofs, sit on top of the roof of the vehicle. Most are glass, but some are textile, and they retract on tracks built into the roof. A third category includes fixed sunroofs, non-moving glass panels designed to let in more light.

Common Sunroof Problems

These basic problems are the sunroof issues most commonly encountered by vehicle owners:

  1. Mechanical problems. Most mechanical problems, such as breakage or loose glass, can be replaced or repaired with a few hand tools. Fixed-glass sunroofs can often be fixed with nuts and bolts. Urethane-adhesive sunroofs, however, might best be left to the professionals.
  2. Sticking, popping, or twisting sunroofs. These issues can be tricky to address. Sometimes, it’s a simple lubrication problem, and greasing the tracks with heavy silicone grease can free up sticky sunroofs and prevent wear. Unfortunately, this maintenance step is often overlooked until it’s too late. Sticking and binding may also be caused by worn or broken cables. The flexible cables mesh with a gear on the motor, but can quickly be ruined if the track is sticking. This is a big repair, and probably not in the realm of DIY auto repair.
  3. Inoperable sunroof. If your sunroof is inoperable, there could be an electrical problem at work, such as a blown fuse (possibly related to lack of lubrication), broken wire, or dead switch or motor. Always check fuses first, then whatever you can access easily. The sunroof motor may be difficult to access, but some automakers place them behind overhead consoles, which can be easily removed. As a DIYer, you might want to leave it to the professionals if repairs require removing the headliner.

How to Repair a Leaking Sunroof

CAD diagram of a typical internal sunroof
This image depicts the location of the sunroof drain at the front of the sunroof water tray.

When considering retractable sunroofs and the problems their owners face, there is one problem that comes up again and again: leaking sunroofs, particularly internal sunroofs. Hearing water sloshing around in your roof can be disconcerting, at best, but water dripping on your head in the rain or a car wash is much worse. Fortunately, fixing a leaky sunroof is usually simple and requires just a couple of tools.

First, check the seal around the glass. On some sunroofs, it will be obvious that the leak is coming from the seal around the sunroof glass. A cracked sunroof seal can be patched up with RTV (room temperature vulcanizing) silicone, which is commonly used in bathrooms. Clear silicone sealer is usually the best choice, because black or any other color might not match exactly. A thin bead of clear silicone will practically disappear.

If the seal isn't the problem, it's time to check whether the drains are clogged. This issue exists because sunroofs, which are built to be able to tilt up and down, are not perfectly sealed. Automakers expect water to drip past the glass, so there is a water tray to catch and divert the water outside the vehicle. 

At each corner of the tray, there are drain tubes that run inside the car, typically behind the A- and C-pillars, through a port near the ground. These drain tubes can get clogged with dirt, insects, and other debris. When the drains are clogged, they stop functioning, and water backs up into the water tray — sometimes right onto your head! 

You can fix this problem with just a few tools from your favorite auto parts and home improvement store. We do not suggest using an air gun to blow out the drains, because this might just blow the drain tubes right off the water tray, setting you up for a more complicated repair. Here are two different methods to consider:

  1. Shop-Vac Method. From the home improvement section, purchase a foot of thin plastic tubing that's flexible and small enough to fit in the sunroof drain. Then, in the plumbing section, you’ll need to find fittings to adapt your shop-vac to the small tube. You probably don’t have to worry about glue, but you might want a clamp to hold the tube to the fitting. Finally, use your shop-vac to suck the drains clean. Be sure to vacuum any other debris from the tray to prevent it from happening again.
  2. Fish-Tape Method – At the auto parts store, ask for a “universal” speedometer cable, usually less than $10. This coiled cable is flexible enough to bend in the sunroof drain tubes, but stiff enough to push through any debris. Uncoil the speedometer cable and fish it down through the drain tube, gently twisting and poking and prodding until you loosen the debris.

These DIY tips will save you time and money. However, the best way to maintain your sunroof to prevent problems from occurring in the first place. To that end, it’s a good idea to clean the water tray and vacuum the sunroof drains at least twice a year. Then, lubricate the sunroof slides to keep them free and prevent wear and binding. Remember, if the problem has gone so far or the repair is too big, there’s no shame in turning to a trusted professional auto repair technician for assistance.