Glani1970

2005 ES 330 started overheating, after I added Coolant it stopped for awhile. Two weeks later it's overheating again and Coolant is bubbling in Resevoir.

LeX2K

#1 cause is cracked radiator look for stress lines/cracks on the top plastic portion especially near the rad cap and rad hose.

nsghtbrwry

Check the rad cap and for a blown head gasket. I'd rent the pressure tester and color-changing test kit from AutoZone or equivalent (they and O'reilly's will give you back the whole deposit, so it's free, even the fluid).

Oro

I hate to say it but I think what nsg(whatever) (dude! get a simpler moniker!) said is a deep concern. If you ran low on fluid, added it, then ran low again, it's going somewhere. Possibly into a cylinder via a head gasket leak.

Head gasket leaks IME on this generation (2002+) are RARE. But, if this car was neglected or abused for a while, not can happen.

Thus, I'd first do a glove test on the rad cap (google it - glove test for head gasket) . If it passes that, then change the thermostat. The fact you said it was bubbling in the reservoir means you need to get serious about this and not drive it until you fix it. It could be what Lexus 2000 said, or nsg&**&& , but it is serious and needs to be dealt with ASAP, not driven.

nsghtbrwry

Lol. Normally it's insightbrewery, but when I signed up to CL there was a length restriction so I deleted all the vowels . Feel free to call me ISB, that's what everybody calls me on other forums I frequent.

LimpnLexus

I know it's an old thread, but I wonder if the O.P. found out what the issue was.