[barclayhound]

Leak in cooling system is significant enough to prevent vacuum and cap from using the reservoir tank, it causes overheating after enough fluid leaks out and for some reason water doesn't seem to go through heater coil no matter how much fluid is in the system. Upon inspection fluid pools on top of the engine block near the water pump. Any possible diagnoses would be appreciated.

 

[1 Lucky Texan]

there are ways to pressurize the system while looking for leaks.

what car/engine/miles, etc

 

[barclayhound]

It's an outback with automatic xmission and 2.5L H4 SOHC 16V FI Engine with over 150k miles.

 

[1 Lucky Texan]

Do you know if the Subaru Coolant conditioner has been used? i suppose you could have an external gasket leak but, the conditioner is designed to stop that.

Subarus often can't simply be filled at the radiator, they need to be 'burped' and or filled in a special way to reduce the chance of trapped air. Since you seem to have a leak, air could be sucked back into the system on cool-down. There are other issues with the cooling system related to thermostats (no cheap aftermarket - OEM preferred), collapsed hoses, radiator caps and headgasket failure and even timing belt/waterpump problems.

was your timing belt replaced at 105K?

post your city and maybe someone can suggest a shop to diagnose your car's problem.

 

[plain OM]

Upon inspection fluid pools on top of the engine block near the water pump.

Water pump is at the left, lower front part of the engine block. Are you sure it's the water pump? Perhaps a second look, and a more detailed description (or photos) of where the water is pooling will help us identify where it could be coming from.