Is the filler hole for the radiator degas bottle supposed to be egg shaped? I'm assuming NO! My cooling system in my 6.0 isn't building pressure when the truck is at operating temp. At first i thought maybe something internal was going on. But there is air leaking around the radiator cap. I ordered a new cap. I removed the radoator cap again this morning and found the the filler hole is egg shaped. I'm assuming it is supposed to be round so the filler cap will seal. I attached a couple pics to show the egg shape.

 

Definitely not supposed to be like that......replace with a new dagas and a ford cap

Why does it look sparkley around the threaded part though?

Did someone put "head gasket repair" in the cooling system?

Are you monitoring your temps?

 

I would think as long as the mating surfaces are flat and the cap screws on tight. Lay a straight edge across it.

 

That's some brown coolant! Rockauto is where I purchased my replacement dorman tank. Even comes with a cap. About $40 IIRC. I would look at the various flush procedures on here and go with cat ec-1 rated coolant after the flush.

 

Do you monitor the actual coolant temperature (ECT)?

 

Definitely time for a new tank. I have used the dorman tank mentioned above and it is a good replacement.