Steam from overheating??
 

I had my low coolant warning come on and because temps were OK I kept driving because I was only few mile from home. When I stopped to a red light I saw some white steam on my mirror. I parked the car and steam continued. Temps never went past 0 on 180 on the gauge. I was only 2 miles from home, but I called my wife to pick me up. We returned 2 hrs later with water. Car had cooled down, so I added almost 1 gallon to get it to full mark and drove home. @ home I looked again and it was not visible @ the tank. So I filled up 1 gallon more and fired it up for a short period of time again. I checked the level, it was OK.

My guess is either waterpump or hose? Any better ideas? Car runs fine.

Most likely a cracked water pump if your car has high mileage. I suggest to bring it to the dealer for checkup asap.

I experienced the same problem, in my case BOTH the expansion tank was cracked and the water pump was bad. Open the trunk and pull back the carpet, look for the "river" Suggest you purchase replacement parts from Suncoast (including the 99610644703 coolant tank cap), click here for their direct link and have an experienced shop install....the dealer will knock you over somewhere in the area of $900 for tank replacement and $1000 for the water pump. Good luck!

I think your temp was reading normal because it wasn't in contact with any coolant. You said you added 2 gallons! I'm sure that's well below the thermal couple and it was only picking up ambient air temp from inside the water jacket. I'm surprised there wasn't a tell tale sign of the coolant leaking out. After adding the coolant did you notice it leaking out? How about running at temp when pressure is up?

Now my question is.. did the coolant drop out at the red light???

I had that happen to my boxster at a redlight.. white steam/smoke comming out of my taillights.. and the car dropped the coolent.

It was towed to The Porsche Exchange. A $70 part broke, the "transcoolant valve" which from what I understand is a valve that regulates the flow of coolant into and out of the engine. Cost me $600 to fix.. they fixed it and pressure checked the system... then my water pump went when they pressure checked the system.. cast me another $1500 total for the pump and labor.

Update:
 

It was one water hose which had rubbed in to something solid. Shop said that they have never seen that water hose so close. So I must thank local stealership which repaired an oil leak just before I purchased the car 21mo and 12kmls ago :rolleyes:

And of course my warranty don't cover the hose. :eek: