I had loads of issues with the cooling system in my 4x4 Sapphire Cosworth when I first bought it, fitted upteen fan switches and still had overheating issues, turned out to be the radiator which was blocked, once fitted with a new rad from Ford everything was ok, ended up fitting all alloy bits and fans that run a lower flow of electrical current. Another problem is the wiring that ford used for the cooling fans is total pish and just not up to the job, if your fans run constantly eg when stuck in traffic the wiring gets hot and just melts, as Glenn says fitting an up rated fan loom is a must as the cars are getting on a bit now.