ventilator noise
 

Hi, I had to repair the alternator of a 911-3.0L motor from a ´79 911 SC, which is built in my 914. So I had to take out the alternator, including fan and air duct. After repairing and building back, the motor makes some metallic ´pinging´ noice, probably caused by the fan blades that slightly touches the aluminium airduct. Before building back into the car I checked if the fan was running free, which seemed to be the case. Probably due to the tension of the belt the fan is not running free now anymore. How can I adjust this? The belt can be moved sideaway about 1 - 2 cm halfway the pulleys of the fan and the crank, which I think is the correct tension.

Thanks for your help in advance, Gerber

Remove the belt and see if the fan spins free without it. If not, I'd suggest you remove the fan/alt/housing assembly and check the tightness of the 6 nuts that hold the alt/fan in the housing. Sometimes if they are not equally snug, the alternator/fan won't sit square in the housing.

Thanks Cogar, removing the belt again might be an idea to check if the fan still runs free without. Do you think it might be allowed for running the motor for a very short while without fan belt to test if the noise really origins from here?

I would say NO, as the alternator will not spin. I'm not sure if you would actually "damage" something running the motor for a few seconds, someone else will know.