997.1 Coupe Sunroof Water Ingress When Stationary - Usual culprits confirmed as not the issue, thoughts?

u05harrisb · 6 Mar 2024

Hey Folks,

I have a 997.1 Sunroof Coupe and am currently finding water in the interior of the car whether it's left stationary outside or being driven in the rain. The water is isolated only to the footwell of the rear passenger seat. At times with the recent heavy rainfall I can be pulling a litre or more every few days which is obviously non-ideal.

Usual culprits have been checked:

Friends Green Porsche fixed any sunroof drainage issues, and I've reconfirmed that they're draining fine and also done the weed wacker trick too
The bulkhead bungs have been removed in the front of the car
I'd adjusted the rear three-quarter window and found no correlation here either
The carpet isn't wet in the vicinity of the door cards itself which seems to therefore exclude the known door card membrane issues some folks have, it manifests only in the rear footwell being wet

I'm not finding anything else wet and I've even pulled the rear three-quarter interior panel off to see if I could find water dripping down the internal body skin of the car, and it all appeared dry despite the recent rain at the time of investigating. It is worth noting that the car is parked on a diagonally slanted driveway meaning that the rear left tyre is the lowest most point of the car, naturally therefore water would drain to this area of the car, but I must confirm that I'm not finding residual damp anywhere else which leads me to believe the footwell is where this leak is naturally draining too and not just because it's where it stops once it's in the car!

Currently, the best guess is that it has something to do with the roof strip gasket as the weather stripping at the end of the car shrinks over time exposing a little gap, or potentially it's as "simple" as the rear window needs resealing, perhaps. What do you think might be a related factor here based upon the knowledge you've got, and what would you consider best actions-on to get closer to resolving the issue?

Thanks in advance!

andrews7889 · 6 Mar 2024

Do you have a rear wiper - they can come loose / or the rubber degrade and leak there - just a thought.
My old 997.1 leaked there until I fixed it.

Good luck and hope you fix it soon.

u05harrisb · 6 Mar 2024

Thanks so much for the swift response! Good thinking - I actually don't have a rear wiper, so fortunately that removes that as a possibility at least!

andrews7889 · 6 Mar 2024

It's probably not that then

spinnaker · 7 Mar 2024

I have something similar that I am trying to pin down at the mo. I get a wet driver's side rear seat after very heavy rain. I have cleaned all the drains out recently. The back shelf is always dry and I have had the door membranes done in the past too. No wetness in the footwell. I haven't checked the rear window seal as yet but will do that in the next day or so. I also checked the rear wiper seal and it looks fine. I'll continue the research. I do wonder if I haven't managed to put a hole in the drain while cleaning it out a few months back.

For reference I did see someone who stripped out their interior carpeting in the same area and sprinkled talcum powder all over to see where the water was pooling from. Bit extreme but seemed to work out in the end.

Chumbaside · 27 Mar 2024

spinnaker said:
I have something similar that I am trying to pin down at the mo. I get a wet driver's side rear seat after very heavy rain. I have cleaned all the drains out recently. The back shelf is always dry and I have had the door membranes done in the past too. No wetness in the footwell. I haven't checked the rear window seal as yet but will do that in the next day or so. I also checked the rear wiper seal and it looks fine. I'll continue the research. I do wonder if I haven't managed to put a hole in the drain while cleaning it out a few months back.

For reference I did see someone who stripped out their interior carpeting in the same area and sprinkled talcum powder all over to see where the water was pooling from. Bit extreme but seemed to work out in the end.

Hey Spinnaker,

Did you ever get anywhere with this? I have a similar issue and have tried all of the obvious stuff. I'm convinced the water gets in between the outer and inner sheet metal skins somewhere, which is why it runs under the rear seat / rear footwell without soaking the headlining etc. I suspect the rear quarter window still and wonder if there's a seal / grommet / bung missing somewhere where the window fittings pass through?

So frustrating!

spinnaker · 27 Mar 2024

So it is still an issue after days of rain but lessening now better weather is coming. I snow foamed and rinsed the car the other day and I saw a few drips of water coming down the inside of the rear driver's side window so I am now wondering if it is actually the rubber window seal rather than the drains or rear wiper seal. I was hoping for a couple of days of dry weather (please god!) so I can pour a few buckets of water over the window and see if I get any wetness in the seat base. It would be a good start to just localise it.

u05harrisb said:
I'm not finding anything else wet and I've even pulled the rear three-quarter interior panel off to see if I could find water dripping down the internal body skin of the car, and it all appeared dry despite the recent rain at the time of investigating.

How does the rear three quarter panel come off? I don't want to destroy it by just pulling at it. You are talking about the inside of the pillar between the rear side window and rear windscreen, right?

drmark · 27 Mar 2024

I had the same issue - albeit with a 911 3.2. Sunroof drains were checked and clear - and strimmer cable went through them - but the n/s had come off a "spigot" and was leaking right at the back and water dripping down rear quarter and soaking passenger rear footwell. Took us a year to find it. Not sure if same set up in 997s bit wouldn't be surprised. Looking here it appears so...

Drain location and cleaning - Rennlist - Porsche Discussion Forums

997 Forum - Drain location and cleaning - I have a 997.2 and I am due 40,000 miles/4 year major maintenance. I have been talking to dealer service departments for estimates. One recommended cleaning the body drains and of course they are wanting an outrageous fee to perform this task. Does...

rennlist.com

spinnaker · 27 Mar 2024

Thanks for that drmark, that is another potential issue. I want to make sure the cleaning of the drains hasn't holed the tube or pushed it off the connection somewhere.

drmark · 27 Mar 2024

The classic error is blowing compressed air through them - that'll blow a joint.

KarlRS · 27 Mar 2024

drmark, that is a very good call. Different car altogether, but my cousin in Germany has a Tiguan with a Panoramic roof. Seals were replaced and the leak still occurred, it was the connection with one of the drain tubes. Can the original poster access a minature optic camera and check the drain channels and connectors?

Chumbaside · 28 Mar 2024

drmark said:
I had the same issue - albeit with a 911 3.2. Sunroof drains were checked and clear - and strimmer cable went through them - but the n/s had come off a "spigot" and was leaking right at the back and water dripping down rear quarter and soaking passenger rear footwell. Took us a year to find it. Not sure if same set up in 997s bit wouldn't be surprised. Looking here it appears so...

Drain location and cleaning - Rennlist - Porsche Discussion Forums

997 Forum - Drain location and cleaning - I have a 997.2 and I am due 40,000 miles/4 year major maintenance. I have been talking to dealer service departments for estimates. One recommended cleaning the body drains and of course they are wanting an outrageous fee to perform this task. Does...

rennlist.com

Hey drmark,

The setup is similar on the 997, in that each corner of the sunroof frame has a plastic corner with a spigot that connects to the corrugated tube. I think the difference is that if the tube is disconnected in a 997 the headliner also gets wet very obviously - ask me how I know

In my case I think the leak is in the b-pillar area, hence suspecting the quarter window leading seal or fitment of the window itself, resulting in water travelling through the quarter and onto the rear seat / floor. Always soaks up through the carpet; has never pooled from the top.

The joy of old cars!

u05harrisb · 16 Jul 2024

Hi everyone,

Thank you all for your patience. I've been troubleshooting a series of potential fixes and encountered some distractions along the way, but I believe I've reached a point where I can confidently share my findings. Hopefully, this will help anyone else experiencing similar issues.

To recap, I was finding water in the rear footwell on the passenger side of the car. Since I don't have a rear wiper, I initially suspected the rear 3/4 window, which turned out to be a red herring. In fact, I ended up introducing a leak in an otherwise un-leaking window—lesson learned there. As mentioned at the beginning of the thread, all sunroof drains were clear and tested multiple times. I also checked the weather stripping on the doors and rear window, which seemed fine when tested in isolation.

Now for the good and bad news. I believe the issue is unique to how my car is parked on a hill, where the rear points downhill and the passenger side sits lower than the driver's side. This causes water to collect in the rear passenger side of the felt weatherstripping/sunroof gasket. The water doesn't just fall into the drain traps but also makes its way into the C-Section where the sunroof rails run.

There are two main reasons for this conclusion. First, when I park the car elsewhere in the rain, it doesn't get wet inside. Second, I pulled part of the headliner back and saw water collecting at the back of the C-Section where the sunroof slides. I believe the water travels down the external part of the sunroof drain hoseline and follows gravity into the footwell.

A simple solution is to avoid parking on an incline that is also canted to one side. I haven't tested a forward-facing incline, but I'm hesitant to risk pooling water in the dash. Regardless, I bought a new sunroof gasket, which is the felt weatherstripping that attaches to the edge of the sunroof opening. It's relatively cost-effective from Design911 and can be installed yourself—just take your time and be careful not to scratch the sunroof while it's semi-retracted. I've noticed a reduction in water ingress, though the gaskets are never truly waterproof.

I hope the above is helpful for those in the thread and anyone searching for answers in the future. If anyone has ideas for resolving the C-Section issue, I'd love to hear them. However, I'm hesitant to modify the open channel's end, as it might create new problems elsewhere unless resolved at its core. Food for thought, nonetheless.

All the best,
Ben

Hertsdriver · 17 Jul 2024

I had similar in mine, took the headlining off and carpets out then tested watching inside with a hose spraying onto the sunroof. in my case the clear issue was the drains becoming overloaded by water so that it leaked from the push fit join of the hose onto the sunroof drain tube. a couple of zip ties stopped it, but nothing can stop a complete overload of water (think really heavy rain like we have had recently) where a large volume of water then escapes over the side of the sunroof channel and down finding its way to the footwells in the rear.

KarlRS · 17 Jul 2024

Could a resolution be to install drain pipes made from a material of a larger diameter? That way, you may not get the backing up
And subsequent ingress. I am not talking hosepipe diameter and of course you will need to find or modify the fittings that go into the pipe from the sunroof?

997.1 Coupe Sunroof Water Ingress When Stationary - Usual culprits confirmed as not the issue, thoughts?

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