Hi all, decided to share my pain with VW community after ~8 months of troubleshooting by VW (Australia). 2013 Mk7 Golf 110TDI is pushing coolant out from the surge tank. Looks like gases enter the jacket under load, accumulate and then rush up to expansion bottled causing it to overflow - overflow pipe is tiny and most of coolant is blow out through the cap threads and sprays around under the bonnet. Done so far to no effect by VW: replaced water pump, multiple cooling circuit pressure tests, replaced expansion bottle, replaced cylinder head c/w gaskets etc., replaced EGR cooler, replaced intercooler, performed engine compression test, replaced some weeping rubber hose. Any idea is appreciated. Love the car but got quite frustrated by now. Few more points: never ever had overheating or gauge temperature moving beyond 90degC; following each "blow out" can clearly hear "hissing" noise coming from the heater core suggesting pockets of gas travelling through the system.