Fixing Sunroof Drain Leaks on the Infiniti G37 and Q50 Before Electrical Damage Strikes
There’s a moment of dread that every G37 and Q50 owner knows—you step into your car after a heavy rain and feel that squish under your feet, and your heart sinks.
That sound? That’s water. And it’s not just water. It’s the beginning of a nightmare that can fry your car’s brain. The Body Control Module (BCM), the computer that controls everything from your windows to your ignition, sits right in the path of these leaks on many models . When water hits it, you’re looking at a car that won’t start, won’t turn off, or throws a million codes .
Here’s the thing about the Infiniti sunroof design—the drain tubes exit through the firewall with little plastic “baffles” or “grommets” that are notorious for clogging or disconnecting . This isn’t a new problem. It plagued the G35, carried over to the G37, and Infiniti still didn’t fix it in time for the Q50 .
Let’s walk through exactly how to fix this before your BCM becomes a paperweight.
TL;DR
The G37 and Q50 sunroof drains are prone to clogging, causing water to leak into the cabin and potentially destroy the Body Control Module (BCM). The front drains are most common, accessible through the A-pillars, while rear drains require accessing the trunk or removing the rear bumper. A DIY fix involves removing the clogged plastic drain end, cleaning the line, and sometimes rerouting the drain through the firewall or trunk. If water has already reached the BCM, drying it might help, but replacement is often necessary. Dealers quote $1,200+ for the fix, but DIY can be as cheap as $5 and a few hours of your time .
Key Takeaways
- The BCM is the real casualty: Water that reaches the front passenger footwell can destroy the BCM, resulting in a repair costing over $1,500 .
- The plastic baffle is the culprit: A small plastic disc at the end of the drain tube blocks debris but easily clogs. Removing it is a common, effective fix .
- Front drains are DIY-friendly: Remove the A-pillar trim and glovebox side panel to access the drain hoses .
- Clearing the line is easy: Use a snake, compressed air, or a flexible weed whacker filament to clear blockages .
- The ultimate fix? Reroute the hose: Some owners run a new hose through the firewall and out the A/C drain hole, bypassing the problematic factory grommet entirely .
- Prevention is key: Regularly test your drains by pouring water into each sunroof corner and watching for proper drainage .
The Anatomy of the Problem: Why These Drains Fail
The sunroof on your G37 or Q50 has four drains, one in each corner . Water runs from the sunroof channel through rubber hoses that exit the car. The front drains go through the firewall in the footwell area. The rear drains exit behind the rear bumper .
The fatal flaw? The plastic drain caps at the ends of these hoses . They have a small opening designed to let water out while keeping bugs and debris out. But in reality, they’re too small. They collect dirt, pollen, and leaves, clogging up completely.
Once clogged, water backs up in the hose, finds the weakest point—usually where the hose connects to the sunroof nipple—and flows straight into your cabin .
Where does the water go?
- Front drains: Water runs down the A-pillar, behind the dashboard, and into the front footwells .
- Passenger side: This is the most dangerous location because the BCM sits right there .
- Rear drains: Water collects in the rear footwells, often going unnoticed until the carpet is soaked .
The Front Drain Fix: A Step-by-Step DIY Guide
Tools You’ll Need
- Needle-nose pliers
- Trim removal tool (a plastic pry bar)
- Phillips head screwdriver
- Flexible drain snake or weed whacker filament
- Compressed air can (optional but helpful)
- Replacement drain caps (optional) or a 5/8″ hose for rerouting
- Dehumidifier or shop vac for drying the interior
Step 1: Access the Drain
- Remove the A-pillar trim. Pry it gently from the top. It’s held in by clips .
- Remove the glovebox side panel on the passenger side (or the equivalent panel on the driver side) .
- Remove the side air vent if needed. On some models, you can see the drain connection through the AC vent hole .
Step 2: Identify the Drain
The drain hose is a rubber tube connecting the sunroof to the plastic drain cap in the firewall . You might need a flashlight to see it clearly.
Step 3: Remove the Clogged Cap
Use your needle-nose pliers to grip and pull out the plastic drain cap . Be careful—it’s easy to drop it into the abyss behind the dashboard .
Step 4: Clear the Blockage
- Use a snake or weed whacker filament to gently push debris down the hose from the sunroof end .
- Follow with compressed air if available . But be careful not to blow the hose off the sunroof nipple—that creates a bigger problem .
- Test by pouring water down the sunroof drain corner. It should flow freely out the bottom of the car .
Step 5: The Fix
Option A: Reinstall with Modification
Some owners remove the plastic disc inside the drain cap before reinstalling it . This allows more flow and prevents future clogs.
Option B: Install Updated Drains
Infiniti reportedly updated the drain design. Some owners purchase replacement drains and install them with a small zip tie to ensure the hose doesn’t disconnect .
Option C: Reroute Through the Firewall (The Permanent Fix)
This is the heavy-duty solution :
- Take a 5/8″ hose and connect it to the original sunroof drain hose.
- Run the new hose through the firewall, behind the glovebox, and down to the car’s floor.
- Route it to the A/C drain hole under the passenger carpet.
- The water now exits the car through the A/C drain—a much more reliable path.
This is more work but guarantees you’ll never deal with this again.
Step 6: Dry Everything
This is non-negotiable.
- Pull up all carpets in the affected area. Water will be waiting underneath .
- Use a shop vac to remove standing water.
- Run a dehumidifier inside the car for at least 24 hours .
- If it’s warm, park the car in the sun with the windows cracked.
Pro tip: If your carpets have a mildew smell, spray a mold-killing solution (like Tilex) on the area before drying .
The Rear Drain Fix
Rear drains are trickier to access but follow the same principle.
Location: The rear drain connectors are behind the rear bumper . You can also access them by removing the side panels in the trunk .
The Problem: These drains have the same clog-prone caps as the front drains .
The Fix:
- Remove the rear bumper or trunk side panels.
- Locate the white plastic drain connector .
- Remove it, clear the blockage, and consider removing the plastic disc that causes clogs .
- Reinstall and test with water.
Test from the top: Pour water into the rear corners of the sunroof channel (carefully, as the rear drains are harder to reach). You should see water exit behind the rear wheels .
What to Do If Water Has Already Hit the BCM
If you’ve already had a flood and the car is acting up, you need to act fast.
Immediate steps:
- Disconnect the battery to prevent electrical shorts.
- Remove the BCM if you’re comfortable. It’s typically under the dash on the passenger side .
- Dry the BCM with compressed air or rice. Some owners have succeeded with this.
- Reinstall and pray.
The bad news: If the BCM is dead, it’s dead. Drying won’t revive it . Replacement costs can be substantial (some owners reported $1,500+ for parts and labor) .
Insurance coverage: Some owners have had the repair covered under their auto insurance’s comprehensive coverage . It’s worth checking your policy.
Prevention: The Best Medicine
The smartest owners don’t wait for a leak.
- Test your drains every few months. Pour water into each sunroof corner and verify it drains quickly to the ground .
- Keep the sunroof channel clean. Use a wet paper towel to remove debris from the channel during every car wash .
- Park under cover if possible—especially during heavy rain.
- Consider the “no sunroof” life. One owner, tired of repeated leaks, simply sealed their sunroof shut with silicone caulk . It’s a drastic move, but it works.
Common Pitfalls
Don’t use a pressure washer near the sunroof. You’ll force water past seals that are designed to handle only light rain.
Don’t ignore the leaks. Even a small wet spot under the carpet is a sign of a bigger problem. The “water will evaporate” approach will eventually cost you a BCM.
Don’t rely solely on the “water bottle test.” A small bottle of water doesn’t replicate the volume and pressure of heavy rain. Some owners found their drains passed a bottle test but failed during a Florida downpour .
Don’t forget the rear drains. It’s easy to focus on the front leaks, but rear drains can flood your back footwells just as badly .
Frequently Asked Questions
How do I know if my G37 or Q50 sunroof drains are clogged?
Pour water into each corner of the sunroof channel. If it doesn’t drain quickly onto the ground, your drains are blocked .
Where is the BCM located?
The Body Control Module is typically located under the dash on the passenger side, right where water from a clogged front drain will pool .
Is this a common problem?
Yes. It’s one of the most well-documented issues on G37 and Q50 forums. Even the QX50 suffers from this design flaw .
Can a clogged sunroof drain cause electrical problems?
Absolutely. Water can damage the BCM, causing issues with starting, windows, lights, and the key fob .
How much does a dealership charge to fix this?
Quotes range from $1,200 to $2,200 . The parts are cheap—it’s the labor to access the drains that’s expensive.
Can I fix this myself?
Yes, if you’re comfortable with basic interior trim removal. Many forum members have completed the fix in a driveway or garage .
What’s the best permanent fix?
Either rerouting the front drain hose through the A/C drain hole or removing the plastic disc from the drain cap to prevent future clogs .
References:
- Infiniti Q50 Forum – Sunroof Drain Flood Discussion
- Infiniti Q50 Forum – Rear Carpet Wet Discussion
- G35Driver – Passenger Sunroof Drain Final Solution
- G35Driver – G35/G37 Water Leaks Solution
- RepairPal – G35 Water Leak Electrical Problems
- Edmunds – QX50 Sunroof Drain Review
What’s your experience with Infiniti sunroof leaks—have you had to fix one yourself? Drop a comment below and share your story!
