If you mean water expansion reservoir then a blown head gasket can allow exhaust gasses or oil to pass into the water jacket.
Probably a bad head gasket or a cracked head.
The same thing that causes soda to bubble when it is poured on almost anything.
There is air in the system, probably from a head gasket leak
would a cracked blocked cause a car to bubble antifreeze inside the reservoir of a 97 ford taurus ?
It sounds like the tank has a leak.
Defective radiator caps or tubes
The radiator cap could be the cause of coolant reservoir overflow or backup. Have the cap checked to see if it is bad.
No, this could mean you have a cracked head gasket and engine pressure has entered the coolant.
A bad head gasket or a cracked head(s).
A bad head gasket or a cracked head(s).
replace your radiator cap...
The antifreeze is low in the reservoir.