96 4x4 sport. Replaced my water pump and hoses 3 weeks ago and t-stat 8 months ago. Soon after replacing the water pump I drove it 800 miles in 4 days without any problems. I have had no problems with the cool system ever. About 2 weeks later i noticed a faint antifreeze smell through th ac vents. I parked for 3 days to go out of town with mf gf in her car. When I started it seemed fin but a
10 min later it was over heating and there was no coolant. I have repleaced all the coolant today and no sign of coolant loss or over heating. My question is what xould cause this. Slow heater core leak or what? All help is appreciated thank you

 

Also I have been driving around all day and no problems

 

Missing coolant is a sign of loss lol. Yes your heater core is probably done. I assume you just refilled the reservoir and not the entire 12 quart system?

 

Do yourself a favor before proceeding with any more repair or work....go to autozone and rent a coolant pressure test lot. It's free. Pressure test the system and see what happens. And make sure your full on coolant. You don't want to tear your dash apart to be wrong about the heater core. Sounds like if you have a leak, it's a notice one. Just look around for coolant dripping when the system is at pressure. Start there.

 

Thank you I will do that tomorrow

 

Also check your oil and trans fluid to make sure they don't look like chocolate or strawberry milkshakes. Coolant can leak through the head gasket or the tranny cooler in the radiator to both those locations and cause all kinds of problems.

 

Also possible your radiator is leaking where the tanks are crimped to the core.