I have a 93 Previa and I’m having coolant leak problems at the engine block. I had a leaky radiator and was refilling it with water instead of coolant then winter came and things froze and the water pump broke. I replaced the radiator and the water pump then added coolant. The coolant made it past the water pump and came spilling out. An expansion plug did its job and popped out when things froze. I was able to replace it. Then I added coolant and it made it past the water pump and past the expansion plug without leaking but now its leaking out the back of the engine at some sort of hose connection that’s bolted on. Anyone know what that ting is called? I suppose it needs to be replaced or a new gasket or something? I will post a picture of it soon.http://i40.photobucket.com/albums/e204/Coctopus/leak.jpg

Could be the water pump went bad.

You can buy a roll of gasket material at most auto parts stores and make the gasket your self. make sure clean the surface and use sealant and let it dry before you refill the coolant system. good luck.