I just filled another 818 yesterday, filled up the first time with the VCP cooling system mod. And you do need to loop the heater hose for proper thermostat operation. This car had the heater hose and oil coolers lines plugged when it came in. I did a full fill and it would keep heating up and i shut it down at 217°. I put the heater loop back in, refilled the system and now it sits at 187°.