Can't find that sunroof leak? Check the four-hole
03-07-2016, 04:26 PM
#1
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Thread Starter
Can't find that sunroof leak? Check the four-hole
Just informational...
Sunroof leaks primarily happen due to some or all of the drain holes not evacuating water quickly enough. There is an inner sunroof seal (which applies to the car itself), and the sunroof seal, which wraps around the sunroof. If water is not evacuating quickly enough, and your seal(s) are compromised, water will find its way in.
There are four drain holes under the sunroof. Two of which exit into the hood compartment (and find their way out through the batter drain hole) and two which exit via hoses that route through the rear wheels wells.
You can easily check the front two with a snake (large gauge wire or etc), and make sure it easily exits out the under the hood. You also need to make sure your battery compartment drain is clear.
For the rear driver side you can run the snake and should also take a turkey baster and pump water though - it should exit very quickly under the car.
The passenger side rear is what I call the four-hole and where I think most of the problems are. Don't try to snake this from the sunroof because there is a very small plastic T you won't get past.
Like the driver side, the four-hole routes down to/through your rear wheel well.... but... there is also a small drain hose coming from where your gas cap compartment is. The sunroof hose and gas cap drain hose join into a very small T-fitting and then to the drain pipe which dumps outside of the wheel well.
The first problem is the drain rate - the diameter of the T is perhaps half the size of the sunroof drain diameter. Take your turkey baster and force the same amount of water down the four hole, and it quickly backs up and exits through the gas cap drain hole and ultimately will back up to the sunroof with sustained flow.
The hose that the sunroof and gas compartment T into is the same diameter as the sunroof hose, but it's simply bottlenecked at the T.
The second problem is debris buildup at and below the T fitting. Because the T-fitting has half the diameter, things big enough to get down the sunroof drain can be easily stopped here. Second, the drain pipe below the T is a little like the J-pipe in your bathroom sink. Things settle here when there is not enough pressure to force them out. As they settle, they accumulate (which was my problem) and lots of goo can build up. You need to pull this last section and clean it out.
If your 944 sees rain and you can't solve the sunroof leak, my suggestion would be to first focus on the drains before giving up in frustration and trying to JB Weld your whole sunroof closed. I believe you could solve most of the persistent leak problems by deleting the T connector and running both the sunroof hose and gas compartment hose independently through the wheel well. For the sunroof hose, you could just join it to the existing drain hose with a 1-2" slightly larger hose and zip ties (so that there is no bottleneck). For the gas compartment hose, just get a longer one and route it to the exit independently.
You can get to all of this by pulling back the carpet on the side of the wheel well. You'll break all of those little plastic buttons, not a big deal.
Sunroof leaks primarily happen due to some or all of the drain holes not evacuating water quickly enough. There is an inner sunroof seal (which applies to the car itself), and the sunroof seal, which wraps around the sunroof. If water is not evacuating quickly enough, and your seal(s) are compromised, water will find its way in.
There are four drain holes under the sunroof. Two of which exit into the hood compartment (and find their way out through the batter drain hole) and two which exit via hoses that route through the rear wheels wells.
You can easily check the front two with a snake (large gauge wire or etc), and make sure it easily exits out the under the hood. You also need to make sure your battery compartment drain is clear.
For the rear driver side you can run the snake and should also take a turkey baster and pump water though - it should exit very quickly under the car.
The passenger side rear is what I call the four-hole and where I think most of the problems are. Don't try to snake this from the sunroof because there is a very small plastic T you won't get past.
Like the driver side, the four-hole routes down to/through your rear wheel well.... but... there is also a small drain hose coming from where your gas cap compartment is. The sunroof hose and gas cap drain hose join into a very small T-fitting and then to the drain pipe which dumps outside of the wheel well.
The first problem is the drain rate - the diameter of the T is perhaps half the size of the sunroof drain diameter. Take your turkey baster and force the same amount of water down the four hole, and it quickly backs up and exits through the gas cap drain hole and ultimately will back up to the sunroof with sustained flow.
The hose that the sunroof and gas compartment T into is the same diameter as the sunroof hose, but it's simply bottlenecked at the T.
The second problem is debris buildup at and below the T fitting. Because the T-fitting has half the diameter, things big enough to get down the sunroof drain can be easily stopped here. Second, the drain pipe below the T is a little like the J-pipe in your bathroom sink. Things settle here when there is not enough pressure to force them out. As they settle, they accumulate (which was my problem) and lots of goo can build up. You need to pull this last section and clean it out.
If your 944 sees rain and you can't solve the sunroof leak, my suggestion would be to first focus on the drains before giving up in frustration and trying to JB Weld your whole sunroof closed. I believe you could solve most of the persistent leak problems by deleting the T connector and running both the sunroof hose and gas compartment hose independently through the wheel well. For the sunroof hose, you could just join it to the existing drain hose with a 1-2" slightly larger hose and zip ties (so that there is no bottleneck). For the gas compartment hose, just get a longer one and route it to the exit independently.
You can get to all of this by pulling back the carpet on the side of the wheel well. You'll break all of those little plastic buttons, not a big deal.
Last edited by raleighBahn; 03-07-2016 at 05:50 PM. Reason: Editing for clarity
The following 2 users liked this post by raleighBahn:
mazdaverx7 (04-16-2022),
SeaCay (04-16-2022)
04-16-2022, 06:14 PM
#2
I have searched and read many sunroof drain leak posts. My '04 Eddie Bauer sunroof drains fine on the driver's side front water passage hole. The passenger side hole is not flowing at all. The soft hose is firmly connected to the plastic nipple discharge from the sunroof tray. That drain is clogged and I'm convinced the clog is where the tube discharges under the vehicle. I removed front wheel well and was happy to find a lot of leaves, pine straw, and wet muddy goop. Thinking this was the cause of my no-flow drain, I cleaned out all the crud collected for a long time behind the wheel well and above my running boards.
Then, I poured some water in the passenger side hole, and still no flow. Trying to find where the tube exits the vehicle to drain. If I can find the end of the tube, I'll suck it out with vacuum.
Does anyone know where the drain tube exits on the passenger side of the vehicle? Or, does the passenger side drain tube route over to the driver's side?
Thank you!
Then, I poured some water in the passenger side hole, and still no flow. Trying to find where the tube exits the vehicle to drain. If I can find the end of the tube, I'll suck it out with vacuum.
Does anyone know where the drain tube exits on the passenger side of the vehicle? Or, does the passenger side drain tube route over to the driver's side?
Thank you!
04-17-2022, 10:22 AM
#3
Rennlist Member
Im glad that I stumbled on this thread. I think this is something to focus on when dealing with water leaks. Just one more solid area to check to ensure that water isn't backing up and entering the car. I've been dealing with water leaks from the sunroof area and I think this is the next thing to check and ensure is clean.
04-17-2022, 06:04 PM
#5
Addict
Rennlist
Lifetime Member
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The rubber drain grommet in the gas filler area of my S2 somehow got pushed to the inside. In the photo above it appears this attaches to the black drain line, or does that black drain line attach to body structure underneath the filler area? I bought a new grommet but it doesn't look like it attaches to another hose, it just routes the water or gas to the inside somewhere. My RR cubby tends to accumulate water. Guess this might be the issue; I'll check it out.