Gargling sound from filler cap?
 

Hello, I'm just wondering if hearing gargling sounds from the filler cap after a hard drive is normal? Is my coolant boiling? Are my coolant seals toast? I went to the Mazda service station today and was told I have a small coolant leak somewhere. I can smell a faint burning smell or something (definitely not a sweet smell)... i don't know if that helps to diagnose anything.

Also... can anyone recommend me a shop where I can test engine compression and maybe cooling system pressure near/in Massachusetts?

Please help me. Thanks!

A small leak allows the system to depressurize and thus boil.

If it is very small leak, the only way to find it may be a dye kit.