So I did a rad swap a couple of months ago, then a water pump, and then a huge flushing session at the dealership.

After I did my water pump there was a loud hissing sound coming from my truck which me and my dad figured was just air escaping from the swap or pressure equalizing. Considering the truck ran fine I didn't think much of it. But I'm just throwing this up on here to see what you guys think. My first guess would be my cap is messed up since it was pretty gunked up from the oil that magically found its way into my cooling system before I did my flush . It still makes this sound when the truck is warming up in the mornings usually sometimes it doesn't.

What do you guys think?

 

If you have oil in the coolant it sounds like a blown head gasket. If it is that extreme the hissing can be exhaust gases coming through.

First check your coolant see if the oil is back in. If not then replace the cap, they are cheep.

First thought when hearing a hiss to me sounds like the throttle body, which is okay if so. But if your sure your hearing it at the radiator then its not it.

 

Its not my head gasket I know that much.
The oil got in my coolant cause I was an absolute idiot and didn't read into the project and just pulled all the lines and let them drain into the same bucket followed by putting it all back into my rad.
My coolant is clean its nice and green.
I guess I'll throw a new cap on the rad and see what happens.