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Mystery staining / mould on rear right seat
Posted: Tue Dec 09, 2025 1:38 pm
by bag o humbugs
The rear right seat of my car has always been stained. Finally flipped it up and saw this black patch in the padding. The internal roof looks clean so I think the water is coming from underneath rather than on top. There is a hole in the metal you can see in the pictures. I have no idea if that's supposed to be there or where it goes but I feel like it must be related to the hole. When I lean the back of that seat forwards, the bottom of the back of the seat (the bit that faces into the boot) is also damp.
I don't want to replace the seat without addressing the root cause so looking for some help from the experts here.
Re: Mystery staining / mould on rear right seat
Posted: Tue Dec 09, 2025 2:00 pm
by SRGTD
I’d also check the boot floor and spare wheel well for dampness / water.
With the mk7 Golf, there are a number of potential water ingress points** at the rear of the car that can result in a wet boot floor, wet rear seat and water in the spare wheel well. It possible that these might also be common to the 6R / 6C Polo;
** potential water ingress points; rear of car (mk7 Golf)
- failed seals around rear light clusters,
- failed seals around the air pressure equalisation flaps (in lower rear quarter panels, hidden behind the rear bumper cover.
- perished grommet on the exit end of the rear hatch handle drain tube, allowing water to drain into the tailgate and then into the boot.
Re: Mystery staining / mould on rear right seat
Posted: Tue Dec 09, 2025 9:39 pm
by bag o humbugs
SRGTD wrote: Tue Dec 09, 2025 2:00 pm
I’d also check the boot floor and spare wheel well for dampness / water.
With the mk7 Golf, there are a number of potential water ingress points** at the rear of the car that can result in a wet boot floor, wet rear seat and water in the spare wheel well. It possible that these might also be common to the 6R / 6C Polo;
** potential water ingress points; rear of car (mk7 Golf)
- failed seals around rear light clusters,
- failed seals around the air pressure equalisation flaps (in lower rear quarter panels, hidden behind the rear bumper cover.
- perished grommet on the exit end of the rear hatch handle drain tube, allowing water to drain into the tailgate and then into the boot.
Thank you. I'll check those. Any idea if that round hole is supposed to be there or not?
Re: Mystery staining / mould on rear right seat
Posted: Wed Dec 10, 2025 7:04 am
by SRGTD
I don’t think it should be but don’t know for certain; I don’t have a 6R / 6C Polo so can’t check my car for you. However, in the YouTube videos at the links below where you can see the same area under the rear seat cushion of the 6R / 6C Polo, the cars in the videos don’t appear to have that hole.
https://m.youtube.com/watch?v=7_4DEKe0hKA
https://m.youtube.com/watch?v=KwFRnSDNv1w
https://m.youtube.com/watch?v=ZDcE3AkYZo8
Hopefully some forum members who do own the same model Polo as yours will check their cars and respond to your original post - easy to check and only takes a couple of minutes. The fuel tank is under that section of the rear seat, so to some degree ought to provide a shield against water ingress through that hole. However, it’s always possible for water to find a way into a car’s interior through something such as a small hole if it’s not meant to be there. Is the recessed channel that the hole is in wet after a) periods of heavy rain b) after you’ve driven in rainy conditions or c) after you’ve washed your car?
Re: Mystery staining / mould on rear right seat
Posted: Fri Dec 12, 2025 7:30 pm
by bag o humbugs
SRGTD wrote: Wed Dec 10, 2025 7:04 am
I don’t think it should be but don’t know for certain; I don’t have a 6R / 6C Polo so can’t check my car for you. However, in the YouTube videos at the links below where you can see the same area under the rear seat cushion of the 6R / 6C Polo, the cars in the videos don’t appear to have that hole.
https://m.youtube.com/watch?v=7_4DEKe0hKA
https://m.youtube.com/watch?v=KwFRnSDNv1w
https://m.youtube.com/watch?v=ZDcE3AkYZo8
Hopefully some forum members who do own the same model Polo as yours will check their cars and respond to your original post - easy to check and only takes a couple of minutes. The fuel tank is under that section of the rear seat, so to some degree ought to provide a shield against water ingress through that hole. However, it’s always possible for water to find a way into a car’s interior through something such as a small hole if it’s not meant to be there. Is the recessed channel that the hole is in wet after a) periods of heavy rain b) after you’ve driven in rainy conditions or c) after you’ve washed your car?
Thanks for this. Does look like there is a circle mark there on the other cars but it isn't a hole. Interesting. I'll seal that and see if it helps. Need to figure out when it gets wet!
Re: Mystery staining / mould on rear right seat
Posted: Fri Dec 12, 2025 11:43 pm
by Tinman
In my car those circles is just colour match cover which feels stick on, if you push it, feel like is hollow underneath, i thought they holes for bolts or screws.
Re: Mystery staining / mould on rear right seat
Posted: Sat Dec 13, 2025 7:14 am
by ciclo
I think this is the best picture I have of that area (6R LHD).
As you can see in the photo, it's also possible that water is getting in through the rubber seal on the door frame.
I suppose you'll have to remove some trim to investigate further.
Re: Mystery staining / mould on rear right seat
Posted: Sat Dec 13, 2025 9:27 am
by RUM4MO
ciclo wrote: Sat Dec 13, 2025 7:14 am
I think this is the best picture I have of that area (6R LHD).
As you can see in the photo, it's also possible that water is getting in through the rubber seal on the door frame.
I suppose you'll have to remove some trim to investigate further.
Unfortunately no picture as "Content not viewable in your region" issue again.
Re: Mystery staining / mould on rear right seat
Posted: Sat Dec 13, 2025 11:12 am
by ciclo
Thank you so much for letting me know.
My sincerest apologies and I deeply appreciate your understanding.
I'll definitely have to change the servers I use to upload images, I imagine this is just the beginning/prelude of what's to come...
Re: Mystery staining / mould on rear right seat
Posted: Sat Dec 13, 2025 9:10 pm
by amer6R
check roof antenna seal it likes to leak
My sincerest apologies and I deeply appreciate your understanding.