In bumper to bumper traffic I noticed a minor amount of steam that appeared to be coming from the right front of grill/hood. Earlier there seemed to be a "gurgle" sound coming from the behind the dash. No change in engine temperature and car ran smoothly. Shortly thereafter I lost heat. The next morning I noticed the antifreeze reservoir level was slightly lower. No apparent antifreeze seepage from the radiator or hoses after running engine until warm. Still no heat. Thermostat replaced 3 years/10,000 miles ago. Any prognoses ??
Gurgle seems to be an air problem. First I'd bleed the system. I've had my heater control valve go bad.
Definitely don't drive it until you bleed all the air out. You can very easily overheat the motor and smoke it without the gauge giving you any warning. When the coolant level drops below the temp sensor, the gauge is no longer accurate, as it will only read the temperature of the steam above the coolant. Meawhile, the head cooks. So, if you find that it is bled properly and still no heat, there may be other issues. Report back.
Come to think of it, I had the exact same symptom on my 1990 Mazda. In the morning I'd see a little steam, then it would go away. Once the car was warm, no steam. Operated fine. The shop tightened the clamp, thinking that it was loose. Next week I was on a flat bed with a broken radiator. The upper inlet cracked.
