anewman

I had a similar issue last week. It was the relief valve that failed on the expansion tank, also what I thought to be coolant from the exhaust, was actually just the coolant from the overflow tube blown onto the open back side of the exhaust tips. New expansion tank, new cap, and new Porsche coolant solved it completely. that's what I get for putting off the expansion tank replacement at every 10 years

Petza914

Can we see pics of the water pump from underneath, and pics of the expansion tank?

I've rerouted my overflow hose with a longer one so it doesn't spray all over everything and won't put any coolant on the tires, which can be super slippery

I run my coolant at the max line when cold. Running it at the min line gives the system very little margin for error if you have a small leak or lose some due to expansion and overflow as there is then not enough left in the tank and will trigger the low coolant error.

I think you'll need to monitor the level and see if you slowly lose coolant from a head gasket leak. If you had a cracked or chunked cylinder it would run out the exhaust or be more evident.

Get ready.....this might be where a UOA is a good idea to look for coolant in the oil as that will tell you one way or the other if you're losing any from the head or cylinders
.

TheMurse

Here’s the best I could manage with my phone, it’s pre-dawn here:

Petza914

If you follow the overflow hose down, does it look like there is just general spray around where the outlet from that hose is. While underway, the wind will carry that toward the rear of the car which may be how it got all over the exhaust tips.

What about around the coolant reservoir cap - is that pink and crusty or nice and clean. If the cap isn't holding the required system pressure, the boiling point of the coolant goes down (Boyle's Law maybe) and that could explain why it boiled and went out the overflow hose when sitting for so long with little air flowing through the radiators. Also look down the side of the reservoir for any while lines. These are stress cracks and won't leak when cold, only when the pressure in the reservoir increases and they open up a little.

If none of those things the thermostat housing has coolant around it and could be a leak source, but I think it's more likely it just got srpayed from above if that's where the overflow hose exit is.