How does one stop water getting into the distributor cap of a citi golf? on 2004 Volkswagen Golf

I have a 2004 1.4i citi golf, now every time it rains water some how gets into the distributor cap and the car starts jerking and at the best of times the engine cuts out. I have tried silicon but to no avail. really need some advice please?

Asked by for the 2004 Volkswagen Golf
poss the orig diast had a seal,call the dealer and see if there is one.