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Coolant purges out system but only after cool down from spirited drive?

Swipes_MK5

New member
Location
Jacksonville Florida
Car(s)
09 Mkv GTI
Hello all,
This is my first post because I am trying to figure out an issue that I have yet to find the answer to already. So I am currently in Helen Georgia for Alpine Volks Fair. Upon taking spirited drives through the mountains the past two days I came back, parked and when I started the car next I had a check coolant light on the dash and the reservoir had little to no coolant. This problem is strange to me as I checked the coolant while I was driving and it didn’t seem to be moving higher or lower too much nor would it have any indication of low coolant and appeared to be operating normally. the first time it went low (below min) I added some, and the second time it was leaking from the bottom of the reservoir and the purge tank from becoming very full as I did not account for the coolant still in the engine. It did stop leaking from the bottom of the reservoir though much before the max line. And then once it stopped it held until later in the day after spirited driving again when it then sat afterword I fired it up again and once again dash light for no coolant focompletely out of coolant.

It’s a strange intermittent issue that to my knowledge has only been an issue after some pretty hard spirited driving as this never happened to me day to day back home but I also didn’t push it quite as much as this.

I also have had to add coolant before on an empty reservoir before and did not bleed the system after which I’m sure is not good, but the fact the car runs fine and doesn’t drop the coolant until after it sits and cools afterword out the purge system is strange.

Any ideas would be appreciated thank you😊.
also it’s a 09 TSI with 173,265miles it has a relatively new radiator, heater hoses and some of the lower coolant lines around the radiator.
 

GTI's

Drag Racing Champion
Location
MD
Pressure test the expansion tank cap to see it is working to specs. & while there might as well do the coolant system.

The cap opening pressure test is between 1.4-1.6bar / 20-23psi

The system testing pressure is 1.0bar / 14.5psi

Temps & pressure in the coolant system get higher when you shutoff a hot engine.
 
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