That's great news! Did you put the old coolant level sensor back on the new expansion tank?

 

No I haven't done anything with the original tank. Unfortunately now I did notice a lot of coolant on the garage floor about an hour after it was parked. Maybe now with the right pressure, it will show me where all the weak hoses/connections are. It ain't over til it's over ...

 

Have you seen this warning on your display? If so, all the other gauges don't matter. hahaha j/k

 

Nah, not yet. But look, the Porsche is over engineered and probably doesn't really need that extra bearing on the end of the intermediate shart. Just drive it ....

 

I had typed a post about this morning's leakage episode, but it seems to have disappeared. I'll re-enter my update:
After driving about 15 miles on local streets, with only two short bursts on the expressway, I parked the car in the garage. When I looked at the coolant level about an hour later, it was again well below the minimum level again. However, no leakage onto the floor from overflow of the expansion tank, and still the coolant odor near the left rear wheelwell/engine compartment. I looked at the coolant tank itself, which now sports a brand-new Porsche blue cap, and I'm starting to suspect it's the bloody tank as well.
Because the temp gauge seems to like to climb slowly (?as coolant is being vented somewhere?), I suspect the water pump is bad. Just not able to move enough coolant around, maybe because it is missing most of its vanes ... ? In a couple weeks I'll do the pump, thermostat, belt, and now the tank. Merde!

 

There is no seal for the level sensor because it does not go through the wall of the tank. You could take it out (turns clockwise IE left handed "thread") and put it in the cubby and it would not leak unless your tank is cracked, which I believe yours is. Unless you smell/see coolant at the front. The radiator end cap seals are also prone to failure.
Attached are pics of one of my cracked tanks. Cracks only noticed by watching HOT engine after long drive on hot day. I could see drops falling onto the muffler when looking over the SAI pump into the quarter panel.

 

Snap the "bleeder" bail up and drive a couple of hot/cool off cycles to see if it burps any air out. Keep refilling the tank, when/if things settle down the tank is full at about 1/2. The rest of the space is for hot coolant expansion.

 

Just before reading your reply about how the coolant level sensor is installed, I had also surmised the sensor might be sensing the level outside the wet part, hence not needing a seal. How clever!

So, I am facing a compound problem to solve, made up of several more component failures ... expansion tank crack, water pump vanes broken, thermostat replacement, plus things I just addressed, i.e., cleaned out the filthy radiators (allowing both fans to work) and put a real Porsche blue cap on the expansion tank. I probably should have realized multiple parts would be failing on a 17-year old Porsche.

I'll check back in a couple weeks to report on progress, when I will have the time to change out those components.

 

Shabaam! Well, there you go! Thank you buddy for clearing that up for us.

 

I am now truly humbled by such a concentration of intellect in the forum!

 

Amen to that! We all learn for each other and hopefully, save some money in the process.

 

It's been bugging me why the temp stays in the '8' and '0' range on the highway, but rapidly climbs at idle well beyond. Running the throttle up to 3,000 rpms causes the temp to drop back into that 8 and 0 range.

My conclusion: That has to be.a symptom of a bad pump impeller. It must be missing enough vanes that it can't pump enough unless turning faster. Of course, running at excessive temps puts more pressure/stress on the expansion tank, which I believe is now leaking.

 

I don't believe that's a valid conclusion. I would be shocked if your impeller is missing vanes with the bearing not making noise or visibly leaking. The behavior you describe is pretty normal for these cars. They don't like to go slow. Beat on the car and the coolant temperature drops. I've seen it many times.

If the age of your water pump (and thermostat) is unknown, it would be a good idea to proactively change them out. Water pumps for these cars are now considered by many to be regular maintenance items rather than something that you just change when it goes bad.

 

I have to assume the water pump and thermostat are original, so yes they will be replaced shortly. The tank was replaced once, but it appears this needs to be replaced almost as often as the oil filter ... it does now appear to have the usual mystery leak. Coolant loss is still in the 1 oz/2 miles range. About the only other things I could imagine are radiators plugged up with gunk or the oil heat exchanger, but that just doesn't seem likely.

As for your comment above that this "behavior ... is pretty normal for these cars", I can't believe Porsche would design the cooling system such that, if left idling in front of a dealer, it would overheat. Not a good advertising message.

 

Is it normal for the shaft connected to the bleeder bail to rise without the bail being actuated? I am assuming it rises when pressure builds in the tank. I noticed it would do this after a drive when the temp gauge was high, approaching ~230degrees. If snapping the bail up is supposed to relieve pressure, it does not appear to be doing this.