Trying to track down a coolant leak on my 2006 v6... There's some white smoke when I first start the engine, only when it's cold (the engine, not the weather), and I'm also seeing some coolant below the throttle body and around the water pump. I don't see any water in the oil (just did an oil change). Since there's white smoke I don't think it's the water pump... What are the chances it could be the throttle body? I know it has coolant lines going through it, could it leak a little bit into the intake, causing the smoke? Really hope it's not the head gasket.

White smoke is normally a warning sign for burning coolant, and these head gaskets generally fail internally rather than externally so that's worth checking for exhaust gases in your coolant or otherwise following up on.

If not that, it is definitely possible you've got a coolant leak at a hose or the WP. The common spot on the waterpump is actually right at the top center, underneath the pulley and it's nearly impossible to see it without pulling the fan/pulley off to get access. It also has the advantage of dripping directly on the belt so it sprays coolant everywhere and makes pinpointing the issue difficult.

The best thing for you to do is going to be pulling the fan/serpentine belt out. Not a difficult job at all, maybe 10m if you know what you're doing.

A black light/ UV light will make the antifreeze glow bright pink.
Can shine it around the engine bay to help track down the leak.
Don't need any extra additives or stuff they sell to make it glow.

Good to know head gasket leaks are usually only internal... I also checked for combustion gasses in the radiator this morning and it looks OK. I replaced the belt a couple weeks ago and that's when I saw how much coolant was dried around the heads. I couldn't find the source, but it looked a lot like how you described the WP leak.

Still not sure what the "white smoke" was... I only saw it from the driver's seat, so I don't really know how much there was. It was about 70 degrees that day, so I don't think it was water vapor. On the other hand, I just moved to a much more humid climate than I'm used to so maybe a little bit of water vapor is expected?

Good to know, I almost bought a UV kit. I've seen liquid dripping from around the water pump so I'm going to go ahead and replace it.

I got a new pump, thermostat, clutch, and hoses and installed them today. It looked like there might have been a couple pinhole leaks, one on the top right and the other on the bottom left. Also the pump had some play in the bearing so it was probably a good idea to replace it even if it wasn't leaking. It was OEM (has both Toyota and Aisin logos), and could easily be the original pump for all I know.

Seems like that fixed it, but I'll update the thread if it starts leaking again.