zach sotz

Hi everybody new to the forum so hoping you guys can help. Ive got a 2015 sierra 2500 6.6 fully deleted with 203k miles thats having a terrible time spitting coolant from the reservoir valve. I get a low coolant warning at least 5 times a day and even after i took it to the dealer and had it professionally done twice. The system is run on a 50/50 mix water to antifreeze and has never overheated causing me to think thats why its spraying out. Have used temp gun to verify this to make sure dash cluster isn’t faulty. This problem has been going on roughly 6 months but its my work truck so finding time to get it to the shop is hard but Im going to list some symptoms its showing below and I’m hoping someone can keep me from pulling my hair out. Things repaired/done Flushed & Burped system New reservoir cap New Thermostat Blown out radiator New fan clutch Pressure tested at 18 lbs SYMPTOMS ITS DOING decent leak from pressure relief valve in reservoir Only leaks when towing under load (roughly 10k lbs) SYMPTOMS ITS NOT DOING no coolant and oil mix no extreme pressure in radiator hose when cooled completely Edited 17 minutes ago by zach sotz