radiator conversion

a few days ago i took my xj 90 to the radiators shop (in mexico) for sevice because a overheating problems and the guy there told me that the problem was the design o f the cooling system and they can modified for 20 dlls plus the 30 for open and clean the inside of the radiator, the guy there just weld a filler neck to the radiator and conect the 2 lines from the bottle together and he said this will solve all the overheating problems i have this for 2 weeks and really worked for only 50dlls i just wanted to share this with you all, i am not sure but i think i need to conect the heater hoses in a different way but dont know how any info

Replace the existing expansion tank and cap with a better one that will hold pressure. I use an aluminum tank from Moroso. Some have found tanks at the wrecking yard that will fit. Try a search on "overheating", "expansion tank", "radiator", "cooling" etc. for some recent posts on the subject.

A filler neck and cap at the tank will not be at the highest point in the cooling system so it will be difficult if not impossible to ensure you have no air pockets.