firstly make sure it isn`t a/freeze from your heater radiator,make sure the drain holes in the engine compartment at bulkhead aren`t blocked,if you remove the door card then check the polythene lining behind it isn`t damaged and have had a few of these with leaks coming from the top door seal which sometimes comes adrift from the motor,you can glue these back on with a good mastic sealer
cdc, April 2012