overflow bubbling and leaking

With so little to go on, the best suspect at this point is a leaking cylinder head gasket. Your mechanic can perform a chemical test at the radiator to verify that. The test only takes a few minutes. It involves drawing air from the radiator, while the engine is running, through a glass cylinder with two chambers filled with a special dark blue liquid. If combustion gases are leaking into the cooling system, the liquid will turn bright yellow.

Here is the guide CARADIODOC is talking about:

https://www.2carpros.com/articles/head-gasket-blown-test

Here is another guide that should help as well:

https://www.2carpros.com/articles/engine-overheating-or-running-hot

Please let us know what happens.

Cheers, Ken