Only 3 bolts holding fan to water pump?

[Hethj7]

I had to replace my cracking fan today. The new fan was smaller and I had to use a spacer between it and the water pump. As I was installing it and tightening the bolts back down, I heard a pop.

The threads popped out of my water pump pulley as I was tightening the bolt. I swear I didn't have that much torque on it, but needless to say, I can only tighten 3 of the 4 bolts back down now. Is it safe to drive around like this or what? I at least need the car tonight.

I suppose tomorrow I should put a new pulley on so that I can run all 4 bolts on it, but am I good to go tonight? I would love to be done with it and hear that just the three bolts will be fine, but I am assuming that is not what you guys will tell me .