Persistent Coolant Venting Under Load: Good Cap, 0 Misfires, 216°F Peak (Graph Attached)

Hey everyone,

I’m dealing with a persistent coolant venting issue on my 2010 Gen 3, and it's driving me crazy. I'm attaching a Torque Pro graph of my coolant temps from a recent long highway trip for context.

The Symptoms: After long, sustained highway trips (ambient temps are very hot right now, around 95°F-100°F / 35°C-38°C), my engine coolant reservoir level drops, and I get pink crust spraying around the cap threads and around the coolant reservoir at sides.


What I've Checked/Done:

1. The Cap & Vent: I swapped the engine cap with a known-good 108 kPa (16 PSI) cap. I also made sure the side overflow nozzle is completely open and unobstructed. It still vented coolant on my last long drive.
   
   
2. Head Gasket Signs (or lack thereof): I am logging all 4 cylinders in Torque Pro, and I have exactly 0 misfires across hours of driving. The engine runs beautifully smooth under heavy load.
   
   
3. The Data (See Attached Graph): As you can see in the log, my engine coolant temp (7E2) fluctuates normally but peaks at about 214°F to 216°F (101°C - 102°C) during heavy uphill highway stretches.
   

If the cap is a good 16 PSI cap, and 216°F shouldn't be hot enough to boil a fully pressurized system, why is it still pushing steam/coolant past the cap?

Graph1: Different temperatures against other PIDs

Graph2: Cylinders misfire graph against other PIDs