Fun and games with a viscous coupling

Gday
Son borrowed my toyota some time back and when it was returned i found the air comp belt wrapped around the fan coupling. As i didnt know how long it had been there i purchased a new viscous coupling , fitted and checked , the damn thing never freewheeled , not at any time after it was fitted. i did plenty of reading and asking questions of the manufacturer , who said that was all ok, fuel consumption went up 1 ltr+/100 .
The last couple of days have been nice so i pulled the viscous fan off again and broke it in half, checking the amount of fluid i noticed there was to much silicon in the coupling, after i removed 9ml had a coffee and checked again ,all seemed to be the right volume so re assembled , tested and the coupling does what it is supposed to do .I must say that last Saturday i did 160plus km at 95 kph all on freeway and the noise was terrible to listen to. Ill do another run and see how the noise is. Have a nice day people.