Mine did this, there was a bung on the nearside front under the scuttle panel that was no longer water tight. Sealed it up with some silicone and have had no problems since.
Also changed the pollen filter twice (every 10k) you should see how dirty they are after just 10k miles!
Also changed the pollen filter twice (every 10k) you should see how dirty they are after just 10k miles!