Leak in degass bottle

What the heck is a degass bottle?

 

Coolant surge tank

Instead of drilling the cap, just crack it loose if you dont want it to build pressure.

 

Is that just a "get you home" fix, or permanent? I'm asking, because the coolant system needs to be pressurized. Every pound of pressure raises your boiling point by three degrees. So a 10 lb cap will put you at 242* before the water starts to boil. It's pretty easy to hit 212* on a hard pull, and when it starts to boil it gasses in your coolant jacket and things will start to overheat wildly without it even looking like you're running hot, because coolant isn't actually touching that part anymore because as soon as the coolant tries to, it phase changes to vapor. Makes it really easy to crack a head without even realizing you're in danger.

You might already know all this, but if you don't, just FYI.

 

Antifreeze boils around 250ish. But 50/50 boils at 223*. As long as you stay fairly cool, the "process" will never start, and you'll be safe.