Dropping Coolant While Driving
 

Well I was driving yesterday when the coolant light began to flash, temp hit 200, so I went home and filled the coolant, which was really low. When looking through the fill, there wasn't any coolant all the way down. I put in about 3 quarts [ capacity 2.5 gal.]
which was a lot of loss. But There wasn't any leaking. [?] The level stayed steady at the 1/2 min-max mark.

Driving today, about 10 miles back and forth, not only did the light come on but the temperature shot up. I pulled into the driveway just as it hit 250.

No check engine light, no other diagnostic light, just the flashing coolant light.
[meter/check codes?]

When I got out of the car, I could hear a loud whine from the trunk.
Opened it to find that the coolant cap was venting hot coolant steam, and of course the loud and unnerving hissing-whine, from the cap.

After a few moments it stopped. Waited till it all cooled down and slowly and carefully removed the cap. Same issue as above. No visible coolant in fill. I again put about 2 quarts, level hit between min-max.

No leaks under car, coolant level hold steady.

The mix is 1 gal. Porsche coolant [bought though Pelican], and 1 gal. distilled water.
Shaken, not stirred to mix. Let sit. Yes, nice and pink when poured.

The coolant tank is brand new, perhaps has a thousand miles on it. Cap came with the tank. Porsche, not OEM. Put on by a reputable shop which specializes in German cars. I screwed that cap down properly, real tight.

No overflow. No leaks. I'm loosing coolant when driving, only.

Any ideas?

Obviously I can't drive it. Next steps is to load it on a flatbed, and drop it off at the shop.

{Poor Boxie}

Thanks, as always!

What does your oil look like on the dipstick? In the oil fill neck? Any coolant under the trunk carpet?

Oil is fine. No spill in trunk, had that experience. Replaced the reservoir 2 years ago . Still have the bruised knuckles.

potentially air trapped in the cooling system?

When did you last replace your water pump?

Air? I don't know...
I never replaced the water pump, and I have no idea whether it was done in the past.
When it cools down around here, I'll open the front engine compartment and see what condition it's in.

I assume with no coolant carried by the pump the car would heat up in minutes.
[See below]

Here's what I did this morning.

I opened the trunk, took off the bleeder cover, added some more coolant to top it to proper measure, and turned on the car.

Ran it, checked the temperature, coolant level, bleeder valve, cap.

After 15 minutes everything OK, checked around and under car for leakage, especially around the overflow tube.

Nothing.
After 30 minutes, I saw the needle just go over 180, at that point turned off the car.
No leakage, boil-over, etc.

HOWEVER

The fans never went on.

Soooo???

I'd also vote water pump...pull the front engine cover and check around pump for leaks and generally check/test workings of pump. If you go so far as pulling off the pump, check to make sure the impeller is intact....if not, you need to do a system flush (or a couple).

... to get the broken/missing impeller vanes out before you suffer a cracked head...