2015 AUDI A3 Quattro Premium Plus Cabriolet.

Yesterday, I spent HOURS flushing my coolant system. Why? My coolant was like TEA and barely negligible as COOLANT. Note I have had no significant issues with overheating, temp gauge always in middle, however passenger vents slightly cooler than left. Otherwise, no major heating issues.

I used a nice negative pressure kit to fill and pulled hose to drain from bottom each time. It got so futile by the end i simply left coolant expansion tank open while running for an hour and kept adding in clean water while the water pump circulated back in. Never got totally clean. best way I can explain this was that this job was like trying to clean mud off the ground in packed soil. All efforts just kept finding more dirt.

My issue: I did this likely 2 dozen times. and over 10 gallons of water. And about 5 commercial flush bottles. IT NEVER GOT CLEAR. Given the symptoms above, I am thinking TRASHED heater core. I am writing to ask if folks feel that is accurate? NO COOLANT LEAKS AS I CAN TELL ANYWHERE.

MY QUESTIONS:

1. BAD LEFT ALONE? LIKE ALL THIS METALIC CRAP GONNA MAKE EARLY DEMIS OF WATER PUMP WHICH WAS REPLACED 10K MILES AGO
2. SHOULD I REPLACE THE RADIATOR ALONG WITH THE HEATER CORE AT THE SAME TIME? FOR SIMPLY GOOD MEASURE? LOOKS LIKE BEAR JOB BUT WILLING TO DO IT.
3. IS FLUSHING MORE JUST FUTILE WITH RUSTY CRAP HEATER CORE? SERIOUSLY, YESTERDAY IT FELT LIKE I GOT NOWHERE. ULTIMATELY, I JUST GAVE UP AND PUT NEW COOLANT IN THERE, ONLY TO HAVE IT THE SAME AFTER A 30-MINUTE DRIVE.
4. WHAT ARE THE ESSENTIAL THINGS I MUST REPLACE HERE--MUST I DO THERMOSTAT? HOSES? WITH THIS JOB PROPOSED?

THANKS!



in the end--the left bottle wins. however now--upon driving with new coolant, again TOTALLY BROWN metallic coolant.