hello mate,i ve been in the bodywork industry for 20 years and i advise you to use cavity wax,firstly spray it along the seams where its weeping out so that it creeps in the exposed seams and seals any bare metal,[dont be shy with it] then wipe off any excess.secondly if you have a small compressor get you hands on a wax gun with a flexible lance on it,with this you can insert the lance in any available holes in your chassis legs pull the trigger and drench the the inside of your chassis legs in wax again this will creep and seal any available exposed metal or small gaps where two panels meet each other,the problem is with welding any bodywork after the manafacture process is that it burns any primer,paint,corrosion protection etc clean off and leaves a black sooty area of bare metal and if its in a panel where you cant get to it to clean it off it sits there rusting,so this is where cavity wax saves you.if you aint got a compressor get yourself plenty of aerosol cans of it and get as close to the area as you can,the mist from the spray will travel and stick to everthing.