[:@]I drove my car for about a mile from home, parked it for about a half hour, then went out to my car and coolant was gushing out the back of my 1999 Porsce 996. I replaced the coolant reservoir 2 years ago. What could cause this. It looks like it is leaking at the water pump underneath the alternator. Any ideas and how much it cost to fix. ????

 

Could be the waterpump, could be the hose, hard to say until you pull it apart.

 

I just had a similar leak occur on my 2001 turbo. Unfortunately, you won't know until it's been looked at. I hoped it was going to be my reservoir, but no such luck. Clean coolant was pouring out. And it was hose clamps which had came loose around the intake or something to that effect. Had to remove the alternator, serpentine belt, etc, etc. No parts, just labor charges. My mechanic felt this happened because my car wasn't driven enough. It did sit for months at a time in a warehouse without ever being started. It even had flat spots in the tires. I bought it a year ago with only 3k miles. I now have 7k.

good luck on your repairs.