Toyota Repair: 2003 Highlander Coolant Leak, coolant level, coolant leak

Question
Coolant level went low, started to lose the heater. I found red residue which appeared to originate from the water pump. I changed the pump and all seemed fine. But on a longer drive, still have coolant leaking underneath. The pump pulley was caked with hardened red residue. I figured this had to be the source. Not sure what to look for now. Possibly my "high temp" silicone didn't work and failed on a long drive heat up. Oil looks fine. Been reading about head gasket issues on this vehicle? Need advice. Will crawl underneath again this coming weekend. Leak ends dead center of car at rear of motor.

Answer
If it's at the rear of the engine it can't be the waterpump that's leaking now, there are some headgasket issues with the 4 cylinder engine, in some cases the headbolts pull loose allowing the headgasket to leak, it usually leaks out the backside so check for that.