ld restart the pickup you could smell antifreeze inside the vehicle. We checked the fluid level and it was very low. We just did a radiator flush and replaced the fluid about 2 months ago. After adding additional antifreeze to return the level to normal we noticed that when the vehicle was off it is apparently losing fluid. My husband has searched high and low and cannot find a leak. Where could it be leaking from? Could it be a problem with the heater core, thermostat or something else? Temperature gauge on dash does not show that the engine is getting hot.