Coolant overflowing

[Cashflo]

I changed my water pump added coolant filter, added 203 deg therm, and put a new degas bottle on.
Im using Cat ELC.
Now if i fill the degas bottle to the min fill line when its cold it will overflow once its it hot about 20 min driving. Then when it cools it goes back down to maybe 4-5 inchs up from the bottom. It never did that before and was always inbetween the min and max fill line regardless of being hot or cold.

Could it be a faulty cap not holding pressure or an air pocket somewhere in the coolant system?

[Turbostang500]

my first guess would be an air pocket.

is the truck getting hot?

is this under normal driving?

[Cashflo]

just commuting back and forth to work empty.

[Turbostang500]

What is the ect temps?

And does the heater work good?

[Cashflo]

just have dummy gauges. and its been in the 60's so i haven't used the heater. I will try it on my way home from work this morning

[Turbostang500]

Air pockets can get trapped in the heater core which will cause you to not have heat in the cab.

I dont know if these things have a control valve for coolant flowing throught the heater core or not
but when i have to fill a coolant system i always run the heater on high to help with air pockets and to give me an indicator that there isnt air in the heater core.

I will be watching to see what you come up with.