Ive had a problem with heater core matrix since last year. Ive diagnosed the issue using vcds ive checked flap motors, all the data and had a 20° difference from left to right, then i proceed to chsnge the matrix core then it worked perfect for 3 months then again. So i started with flushing whole circut with water then added destilled water a then radiator flush. After all that ive installed new nrf heater matrix core. Last night it happened again passenger side warm and driver side hot as hell. What to fo wity it now? Changed it for the third time? Flush it? Dont know what to do and Im tired of it already. Someone hade similar issue?

( no silikat in the bank, changed couple of time to g12evo, no problems with flap motors, as skoda says my car went through procedure of flushing in 2020)

To be fair, that sounds more like a flap or control issue than a problem on the cooling circuit. Does your car have 2 zone climate control in the front? My sneaking suspicion would be that one of the cabin or vent temperature sensors is giving spurious readings.

Flaps are okey I disassembled 2 of them anf they work fine on car and off it. I have 2 zone climate control. Every changing of heater matrix core resolve the issue so thats the cause. My question is: what to do to clean the whole circuit?

Edited 58 minutes ago58 min by Crux27

It's a questionable practice, but my favourite way of cleaning a coolant system is to throw a dishwasher tablet in.

Can you get any live data from the temperature sensors?

First image left- right went temp sensor

Second pic second core I've replaced

Latest heater matrix core and sensors.