responses are below...
When you start the car with AC on full blast, do the front fans come on?

 

Thanks. All very sound advice, and I'm compiling my parts list now, including the drive belt. I'm curious about one thing left. This coolant problem was first detected during my first test drive, and the temp gauge did NOT register a problem on those test drives (granted it was a 45degree day in February). I could definitely smell the antifreeze after every drive, noticing it when I stepped out of the car. The selling dealer (BMW) and the one who did the PPI (Porsche) both stated it was just probably from the car not being driven a lot. Seemed plausible at the time, but now it is clearly bad advice from them. Also, maybe my nose is now highly attuned to sniff it out, having had coolant leak issues on some of my prior cars, e.g., Austin Healey, Jetta, MGC, BMW 635. The smell of glycol is something I pick up quickly.
Also very puzzling is there is no obvious evidence of WHERE it was coming out on the Porsche. The only time I saw anything was this past weekend with the overheating and the blue cap was bypassing coolant, which then went down its overflow tube to the ground.
So with no initial evidence of overheating, but clearly there was coolant being lost, where else could the loss be occurring? Should I at this also just replace the cap? Am I possibly dealing with something more than a bad cap on the coolant expansion tank? The cooling system with the existing blue cap seems to hold pressure for several days of no driving. I can hear air escaping under pressure when I remove the cap. Is it relevant that the tank fluid level usually then rises, even overflowing? Also, I hear gurgling as I do this. Is this because air is in the system and needs to be purged? Can't believe this is so mysterious. Probably a simple root cause that I'm missing.

 

If the part number on the cap does not end in "04" you have the old style cap which was prone to leaking. One caveat - I read one account where someone added the new cap and the increased pressure caused his old coolant expansion tank to crack. It was likely ready to go and the new cap pushed it over the edge. If your tank has yellowed, it's probably wise to swap that out as well.


With a MY 2001 with little or no maintenance history I would replace the following:

Water pump (OEM with composite impeller and OEM metal gasket)
Thermostat (Low temp 160f)
Serpentine belt
Coolant tank and cap (OEM from Germany, Cap part number ending in "04")


Even if none of these items are the cause of the leakage, they are things that should be done anyway.


2 gallons in 500 miles is a lot of leakage.

 

Pump, thermostat (low temp) and belt are definitely on the to-do list. The expansion tank looks brand new (bright white) and the cap is the new blue one. See attached photos. No part number on it however. Says 'Germany' on it. A clone perhaps?

 

I would go with the genuine Porsche cap (blue, ending in 04). Someone on another forum had a problem with an aftermarket cap.

 

So a real Porsche part would have the part number on it? This one, although bright blue, has no part number on it.

 

Here is the latest Porsche cap.

 

At this point we can't tell if the cap is the problem, but you can eliminate one variable by putting on the proper cap.

 

Made the drive of 20 miles to local Porsche dealer and bought a proper cap, with part number molded in. Wasn't sure I was going to make it all the way to the dealer because the low coolant light went on just before I got there. The expansion tank was on the Max lone when I started. Interesting that the temp fell from over the right edge of the '0' in stop-and-go traffic to between the '8' and '0' on the temp gauge while driving at 60+ mph on the expressway. Drove all the way back with light still on. Will now let it cool down so that I can top it up and put on the new cap. I am eager to see how it behaves ... hopefully some improvement and proof it was only the cap leaking.

 

Sounds like you may have a faulty coolant level sensor. This may be the source of the leak that you smell. Good news... Those sensors are pretty cheap - $40. Bad news - You'll have to remove the coolant reservoir. (see pic)

 

I was hoping, given the apparent newness of the tank that I could avoid the gymnastics required to get it out. Your assessment does make sense though. If the sensor was leaking from its location at the bottom of the tak, shouldn't I be seeing evidence of the leak?

 

My theory is based on the fact that you're getting a "low coolant" MIL while you've confirmed the reservoir tank is completely full. You could have a extremely small leak that is dripping onto the hot exhaust which would give you the glycol cooked smell. But the leak is not large enough to create a puddle under the car while parked. Remember, the coolant will more likely to leak while running since it's under an enormous amount of pressure. While the car is parked, the pressure subsides and thus, doesn't produce a puddle. Just my theory. Seems like you're making the right steps. I'm still hoping your water pump impellers are still intact. Keep us updated!

Also, the coolant expansion tanks are also prone to leaking. If you choose to replace the level sensor, I'd recommend installing an OEM coolant expansion tank to be safe. They're a PITA to install and so it's smart to save the trouble in the long run just in case the sensor wasn't where the leak was occurring.

 

Actually the low coolant light is not on when the tank is at or above MIN. Today, when I took off for the drive to the dwalee, the tank was at MAX and the light was not on. It was after maybe 15 miles on the highway that the light came on. However, if the seal around the sensor is leaking, that would explain the loss of so much coolant.
I am wanting to keep the coolant temp from rising so much in stop-and-go traffic. That points to the pump and belt replacemnet task.

 

In the image of the replacement sensor, I don't see any grommet or sealing ring. Is there one that would come with the sensor?

 

I don't believe there is any type of rubber seal for the coolant level sensor. Now, you got me wondering how it provides a non-leaking seal under pressure. ha!