Valve cover keeps burning..

I Have a 2013 f150 3.5 ecoboost. Valve cover keeps burning on passenger side. What is causing this? Cover looks fine from inside so it can’t be the valves.. I’m just confused. I replaced the burnt valve cover with a brand new one and same burn. Same spot. Weird. The water coolant line that runs beside it gets really hot but I don’t think it’s causing this burn.. are coolant lines supposed to get hot to touch? Thank you