Lexus GS430 loosing coolant out of the overflow tube

[Gs430Ger]

Hey guys, just bought a 2000 Gs430 and noticed a coolant leak coming from the overflow tube (and also a bit from the reservior cap itself). Topped ist off a bit today (around 200-300ml) and as i put the cap back on, i noticed coolant pushing out of the reservior tube (right below the reservior cap)

Added a picture of my engine bay, as i noticed, that there are different versions cooler and reservior versions on the 3uz-fe.

As i dont have the radiator cap, as US most US spec 3uzs, could the problem occur due to much pressure in the cooling system? The timing belt and waterpump was replaced 20k kilometers ago, the radiator is approx. 15k Km old (OEM Toyota/Lexus one).

[TigerFish]

Is it being over filled and not enough space left for expansion?

With the cap off, are there any air bubbles being expelled?