Coolant Reservoir Tank

[Shotgun74]

If it passes all the test, replace the reservoir. I experienced the same problem with coolant getting into the overfill side. We replaced 5 reservoirs all of them oem & finally the problem is fixed. We also replaced radiator, cac, water pump & the issue was still there. Finally the last reservoir TRP brand & I'm no longer getting coolant in the overfill compartment. Local dealer said they chased & replaced 6 reservoirs on a truck they had 2 months ago. I'm thinking the oem had a bad run on those reservoirs.

Good luck!