Circling back to my original question about pressure testing the system. Turns out the loaner tool was broken. Not particularly good if you're trying to test for leaks and the tool itself leaks. Borrowed another one that seems to work. Hooked it up and heard a leaking sound coming from around the reservoir. I couldn't find where it was coming from. Fortunately or unfortunately no coolant seemed to be leaking under pressure, so I couldn't try to trace that. In order to get a better view and try to locate the sound better, I decided to take the rear bumper cover off to get a better look at it -- I've done it several times and it's easy enough. After this it sounded like it was coming from a part near the reservoir. I looked up the part number and it's a bleeder valve, which was left open. The service manual suggests that it's supposed to remain closed unless intentionally bleeding the system. Right now this is my best guess as to where my coolant is going - leaking out the bleeder valve. Could be worth while to check to see if your bleeder valve is open or not. Note: you don't actually need to take the rear bumper and airbox off to get at the bleeder valve. I only did that to try to localize the leek.

I got tired of pumping, so I hooked it up to my air compressor regulated to 15psi.

The bleeder valve

Valve open

Valve closed

 

If you popped off the fan cover, the bleeder valve would be visible? How does the shorowd around the oil and coolant caps come off? Thanks

 

You probably need to also remove the cover that the oil and coolant caps screw onto. That cover is held on by a 10mm hex bolt on the right edge. Once that bolt is off, you should be able to slide it up and out. You may have to wiggle it around a bit but it comes out. The oil fill tube connects directly to that cover while there's a hole for the reservoir cap. You can either move the cover and oil fill lines out of the way or remove the oil fill tube by compressing the clip with some pliers. When reinstalling the cover, make sure you slide it into its track or else you won't be able reinstall the bolt. Ask me how I know that.

 

Good info. I did have an oil leak at the separator and believe coolant system was drained to do the repair.

 

So back for an oil change after clocking 6k miles and have added 1.25 liters of coolant. Most of the coolant was added in the first 2k miles and .25 liters in the last 2k miles. I have not seen any leaks and dealer pressure checked the coolant system with no leaks as well. Sounds like it does take some time to get coolant fully topped off after the system has been disassembled. Also informed by my SA that water pump has an extended warranty until 2028.

 

A coolant system vacuum tester like this Schwaben unit is very easy to use and should purge the system of air. Then reintroduce new coolant to top off.

https://www.ecstuning.com/b-schwaben...SABEgK3O_D_BwE

 

@LexVan So this idea that it's normal to keep adding coolant every month or so is new to me. I don't drive my car as much as others but I've only added coolant to my system once in about 3k miles. What is the normal burn rate on coolant? How is coolant lost? Where does it go?

 

Hi T1T. I'm not suggesting that it's normal to need to keep topping up the coolant volume. I'm just saying that it's normal that the coolant level reads minimum. And when you do top it up to above min, the car usually expels that extra volume, and reads min again on the next check.

 

Ill give a differing view based on my 19 C4GTS. With coolant in the mid range between min and max, it will stay there. I don’t end up at min.

Seems like the flippy do purge valve thing has been left in open position on cars that have had some service. For those that are adding coolant and are ending up at min again, checking this would be prudent.

 

Is the purge valve accessible/easy to see and determine what position its in?

 

Lexan:

That’s my question as well. To me cooling system is a closed loop. Loss of coolant usually means a leak somewhere. But, maybe there is a place where extra coolant is purged off? Anyhow I’m going to do an oil analysis on the next change to confirm there’s no water in the oil.

 

Post #16 has all the info you need.

 

My 991.1 S does the same than what LexVan describes: I fill the coolant reservoir until the little ball is in the middle but after a couple of weeks driving, the ball is back to the minimum level. Then, the coolant level still stable. After testing the cooling system under pressure and having the dealer looking for an issue, I came to the same conclusion than LexVan that the coolant level indicator is not very useful and the car just purge coolant if the reservoir is filled until the ball is in the middle.

 

I had almost 78,000 flawless miles before I sold my car in early April. Never leaked an iota of any fluids. You can do a simple experiment with about 200-400 mls of distilled water. Top off your overflow reservoir with distilled water, till the bobber is in the middle. Drive for a few days. Recheck. It will be back to "min".

Yup.

 

And I even used a measuring tape to check that the actual coolant level doesn't continue to drop after the ball is on minimum. After measuring every week for one month, I stopped. Just measured again, and same level since I checked during my last yearly service in January: 3" from coolant level to the yellow ring. And yes, I know that I have OCD