Camry coolant leak, need help

My first post here. My 1995 Camry, 165000 mi, 5S-FE engine has a coolant leak, pretty bad, around 1/2 cup/min. After replacing the water pump, which I figured must be it, the leak increased to the above rate.:banghead: I was afraid to drive it with that much of a leak.

The leak, on very close inspection, appears to be coming from the back of the block, inboard and slightly above the PS pump. The is no connection or joint in the area, just a 1" circular depression cast in the block.

Someone mentioned freeze plug as a possibility, but my official Toyota shop manual doesn't mention them at all.

Is this a freeze plug leaking? If so, is it a DIY job? Looks like the intake manifold would have to come off at a minimum, and I get really nervous about repairs without good directions/pictures. How much should it cost to get repaired at a shop/dealer?

Yup, it sure sounds like a freeze plug. It's like a soda bottle cap that's pressed into the engine. They do rust out and can leak just like you described. To remove the old one, you take a small chisel and tap one side of the plug so that it pivots the opposite end out enough to grab it with a pliers. To install the new one, you coat it with sealant and tap it into place using a socket or a freeze plug installer tool. The advantage of the plug installer tool is that it won't allow you to pound the new plug in too far. It has a flange that stops the plug at the right depth. You won't find this mentioned in any shop manual because it's fairly rare and it's also considered basic auto 101. The risk you run in learning on this one is that you might pop either the old plug or the new plug into the engine. You cannot leave it in there. It has to come out and that's a real PITA. The biggest limiting factor in doing this yourself is space.

I have a 2003 2.4 liter Camry that is leaking water behind the block. I have tried to locate the leak, but with no success. Hard to see where it comes from. I am afraid it could be a head gasket related leak...any other potential cause? Car has 310 000 km's on it (200 k miles).

Edit: now it is for sure, it is a head gasket leak......any experience how likely it is that both the head and the block are gone....or is this usually just a standard gasket replacement + reworking the head?