The pipe was not clogged. Only carbon build up in the wall. The intake manifold is the one that has goo puddle.
Update: Now every problem that previously appear has... Reappear. Goddammit. I'm out of idea. Honestly. Might just bring it to a local mechanics.
I'm thinking of using sealer like Blue Devil or Steel Seal. Any video to show me how to do it properly since I don't know where the thermostats and radiator cap on Prius 2010.
I'm gonna just buy 32oz Blue Devil, drain the coolant reservoir for the engine, make sure the engine is cool, plug out the top coolant hose, put it slowly there while having the engine run.
I would never used that sealant stuff, gum up the entire cooling system, and engine as well since it's leaking. I would replace the head gasket, if it's for sure the issue. Did they do a leak-down test to confirm?? $3000 grand is steep. These guys are kinda cutting corners, not the cleanliest, but I heard they're around $860: Just foood for thought, what the job entails. They basically replace JUST the head gasket, which is around $140.