P38’ers - I need some ideas about a water leak under the carpet on the drivers side!

The leak is more towards the door side and spans the footwell from a few inches in front of the BECM to the accelerator pedal. It is completely dry next to the centre tunnel and also completely dry at top edge if carpet against the bulkhead all the way across, so only about 1/2 the carpet is wet.

• sunroof drain is clear
• air con drains clear and no leak from matrix - centre tunnel and that side of carpet is dry, and it tastes like rainwater rather than coolant
• no leak on headlining (completely dry under headlining) or pillars at all
• it’s not the windscreen as that is less than 6 months old and top edge of carpet against bulkhead is dry
• I fixed up and sealed tears on the door foam/water deflector foam behind the door card already
• no water coming through the heater blower box anymore as I’ve fixed this leak by taking out the scuttle and pollen filter box etc. and sealing and repairing the area, sealing pollen filter covers erc as well as new inserts etc for scuttle area.
• grommets for bonnet cable and bulkhad cables look ok but have siliconed those

I’m a bit stumped and can’t think where it could possibly be coming from - any ideas?

It sounds as though you have dealt with all the likely places. Are you sure it is still coming in or if this isn't just water that got in there before you fixed the leak and hasn't evaporated away yet?

You could try removing the knee panel, kick panel, internal windscreen pillar trim,plastic sill threshold and doorcard and get inside with a torch whilst someone plays a watering can over the lower a post area door hinge and slowly working their way up to the roof.

Gilbertd wrote:

It sounds as though you have dealt with all the likely places. Are you sure it is still coming in or if this isn't just water that got in there before you fixed the leak and hasn't evaporated away yet?

I did think that - but I dried the underlay out with a haridryer so it was touch dry, and by the morning it's wet again (even after a dry night!). I did wonder whether it might effectively be remaining moisture / condensation etc but it's to the extent that you can feel it on the floor.

I've wracked by brains as to any other sources of internal water but the washer lines run outside the car, and I'm pretty confident it's not the heater matrix or air con drains as that side of the carpet next to the centre tunnel is absolutely bone dry!

I've also made sure the sill drains are clear.

I am completely at a loss as it seems to be happening even after a dry night!

Chrisp38 wrote:

You could try removing the knee panel, kick panel, internal windscreen pillar trim,plastic sill threshold and doorcard and get inside with a torch whilst someone plays a watering can over the lower a post area door hinge and slowly working their way up to the roof.

I've stripped it all out and there isn't any sign of water ingress at all - I'd normally expect some element of remaning drips and the top of the carpet up against the bulkhead etc is completely dry

It's almost as if it's coming up through the floor itself!!

I replaced the heater core O rings on one car that had been leaking for quite a while (owner had been topping the coolant up on a daily basis for months) and the amount of coolant that was retained in the foam under the carpet had to be seen to be believed. This was on a Vogue where that foam is a good inch thick. We used a wet and dry vacuum cleaner to get what we thought was a lot of it out but it still kept coming. The owner ended up putting old towels under it and propping the foam up to allow air to get underneath whenever he wasn't using the car until it was dry but that took weeks. So if any appreciable amount of water has been soaked into it, it will need a lot more than a hairdryer......

Gilbertd wrote:

I replaced the heater core O rings on one car that had been leaking for quite a while (owner had been topping the coolant up on a daily basis for months) and the amount of coolant that was retained in the foam under the carpet had to be seen to be believed. This was on a Vogue where that foam is a good inch thick. We used a wet and dry vacuum cleaner to get what we thought was a lot of it out but it still kept coming. The owner ended up putting old towels under it and propping the foam up to allow air to get underneath whenever he wasn't using the car until it was dry but that took weeks. So if any appreciable amount of water has been soaked into it, it will need a lot more than a hairdryer......

yes, there was alot of water in the foam - if I squeezed it it would run out onto my hands. After using a hairdryer a few times and paper towels etc, it felt largely dry to touch but then the next morning the floor is wet again. Do you think it can "sweat" out the rest of the water overnight for example?

Conscious I might be chasing a leak that no longer exists, but the amount of dampness made me think there is still a leak. it's baffling!

ps mine is a Vouge with thick underlay

Get a dehumidifier in there? I've read that works well.

Chrisp38 wrote:

Get a dehumidifier in there? I've read that works well.

I've got a small one but I'm torn whether to go down the route of getting a bigger one running in there, as I'm really baffled as to whether it's just old wetness or an ongoing leak!

If you squeeze it until it feels dry, leave it overnight without any further wetness and squeeze it again. I suspect you'll get the same amount out again. It really does hold a lot of water.

Update! Took the door card off again, and it would appear that despite my previous taping up of the foam liner last time, the door was holding some water which might have been then leaking into the car.

Also put a decent door seal on and sikaflexed the groove before fitting.

Sealed up with Sikaflex and also propped carpet up to give it a fighting chance to dry so lets see how it goes overnight as it’s due to rain!

You will still need to use a dehumidifier for a few days to dry it out, ideally with the carpet lifted as much as possible. The only other way is to take the interior out, and hag the underlay indoors for a week !!

I had to do the remove & hang method on a Z3 last year. Took 10 days for the underlay to dry properly.