Over the last few weeks my car has got very damp inside (1999 Octavia estate).

There’s no obvious sign of water access, spare tyre well as a tiny bit of water in but nothing major and I can’t see anything anywhere else.

The inside of windows are very damp and now the carpets in the boot are going mouldy!

Has anyone got any idea how water could be getting in.

Ta!

Has it been out in the big storms / parked under a tree ? The windy / wet weather can drive water in through quite small gaps. I would check the windscreen drain under the bonnet and see if it’s blocked with leaves / pine needles / other gunk. I am aware of similar problems with other cars due to drain being blocked so water gets into the car. Is there anywhere which is particularly wet inside the car ? I would also check to see if the external rubber seals are good on the windows and if the drain holes are clear in the doors (if the car has them). Likewise around the tailgate.

Plan A would be to dry the car out, ideally with a dehumidifier, and then see if it returns and also this might identify where the water is coming from.

I had an old mini back in the day and water used to come in through front footwells due to rust issues.

Has it got a sunroof? could be they drain channels are blocked and waters running back in to the car via the sills.

Heater matrix leaking.

Door seals leaking.

Few things to look at there.

Some VAG cars of that era seem to have an issue of ingress through either a blocked battery well or seal failure on the pollen filter. Water reservoirs under the battery, up to a few inches deep, and then seeps past the wring grommets and brake servo and down the bulkhead. ECU or other electrical problems follow, plus the moulding of flooring.

Search for ‘Passat B3 water ingress’ for the most info.

mine, and my mates for that matter, old Golfs used to have terrible water problems – such that I’m sure his was growing mushrooms in the boot! was a common problem with old Golfs of that era, the window water sheeting used to tear and rather than water flowing down windows, into doors and out the drain holes, the sheeting was torn and the water flowed into the car..

Not sure on the estate but on the hatchbacks the seal in the wiper motor goes and screenwash goes straight into the boot.
Does your rear washer squirt?

Its your air intake for the heating, it gets blocked with leaves open bonnet and clean out the well at the back of the engine bay.

I had a Skoda Fabia of 2004 vintage that suffered bad with damp. IRC It was to do with the air vents into the back, the rear footwells were usually wet as a result.

hatchback or estate?

if hatch check the boot struts – the mouunting works loose and flexes the spot welds, loctite and retighten, seal any cracks with sealant

also roof channels have a habit of developing very fine cracks and seeping in water – is your drivers seatbelt damp?