changed diesel filter on kangoo van. now have problem with air entering the fuel line. new filter looks slightly different from origonal but was told that it should do ok. when changing filter i tried putting seal on top of filter, but when i did this the filter leaked. i ended up putting seal between filter bowl and filter and then fitted filter head. i dont know if this is right. can anyone help with this problem or tell me the correct way to assemble the filter unit.