With the amount of coolant that you're losing it should be very noticeable. You can pull out the airbox and secondary air pump with not much effort. That should enable you to reach in and feel the underside of the coolant tank. It could also be a crack in a radiator or coolant hose that doesn't show up until it's under pressure. There are three small hose connection on the expansion tank. Check to see if any of those are wet. Just because there is coolant on the bottom of the tank doesn't mean it began there.


One other thing to consider. You said the tank looks new. Some people have reported problems with aftermarket tanks right out of the box.

 

Like we say about the internet, "it's magic!!"

 

BTW, that last post of mine was directed at 'b3freak's previous comment about how the coolant level sensor is sealed to the expansion tank.

To 'wyovino', I have felt from the very beginning that the amount of coolant loss was just too big to not be detected somehow, somewhere. I will probably be replacing the pump, thermostat and belt in mid August, when I'm back from some travels. At that time, I will do a more thorough manual inspection of the coolant tank. And maybe a deeper inspect of the rest of the coolant hoses throughout.

 

Btw - Here is the coolant level sensor. There is no o-ring or washer, so you're right - it is magic. Notice the crack in mine. Unfortunately I broke it when I installed my new tank and had the privilege of doing it all over again.

 

So how on earth does it hold pressure?

 

German engineering.

 

And I have a bridge I'd like to sell you ....

 

That's really a good question, but we must realize that the coolant level sensor is located at the bottom of the reservoir. Higher pressure resides at the top. Imagine boiling water in a sauce pan... where is the energy released? Get my drift?

However, I'm still baffled at how Porsche achieve a proper seal with plastic on plastic. Even at very low pressure, seems like coolant would still find it's way out.

 

I don't want to sound like a physics professor, but if you have 15 psi at the top of a container of liquid, it also has to be 15 psi at the bottom. Any difference in pressure would cause liquid to move from the higher pressure to the lower pressure area, causing them to equal. That's equilibrium.

Your more important point is how in God's name the plastic on plastic seals at all. Mystery ...

And one other question tp ponder ... do new expansion tanks come with the sender already installed?

 

No, the sensor does not come with the tank. When you install the sensor, it twists and locks rather firmly.

 

Any gasket cement or o-ring involved?

 

I must have fallen asleep in science class. haha I was thinking the vaporized state (at the top of a container) would exhibit increased pressure greater than the expanding liquid state as temps increase. Oh well.

 

I think you were right the first time. I had a flat tire the other day but it was only flat on the bottom.

 

bwhahahahaha!!!!! Yea, I better stop while I'm ahead! Thx Bill.

 

Seems the non-Porsche brand expansion tank cap was a major culprit (but probably not the only one). Put a proper Porsche one on yesterday and drove maybe 20 miles just now. Can't say I noticed any leaks or as much of a glycol smell. Temp stayed between 8 and 0 on the gauge while on the highway, so no real change there. The temp needle did climb above the 0 just as I got home, so maybe those other tasks (pump, thermistat, belt) will fix the rest . of the issue. I will also keep an eye on that coolant level sensor under the expansion tank for leaks. I did notice that both front fans were running well, along with the one over the engine bay.