1992 Honda Civic DX issue

Add coolant to the radiator and overflow bottle with the engine COLD. Replace cap and start engine. Look around the top of the radiator for leaks. If no leak is found there, look underneath the front engine area (driver's side where the accessory belts are) for coolant dripping on the ground.

A very slow leak can be monitored while still driving the car short distances. If the leak is from the top of the radiator, and not too bad, you should be OK for the next couple of days. If it is from under the engine (water pump most likely) then I would suggest you let it sit until your repair appointment.

The fact that you had no heat is proof enough that you were dangerously low on coolant. Perhaps you had a slow leak and did not notice it until now, or perhaps the leak is a gusher that just opened up. Know which one it is before you attempt to drive any further.

Toyota MDT in MO

You drive this with a leak at your own risk. Top off the tank of course. That does not guarantee that air won't be in the system. Trapped air can cause local heating and blow a head gasket. Many people go on for weeks or more topping the fluid off regularly. Others do severe engine damage in days. The newer the vehicle the less chance you will get away with it.

If I where u, I would not drive the auto any more than I have to. Honda's have aluminum heads which are very prone to wrapage and or breaking. This can be a very expensive proceedure

An improperly bleeding on certain motors can blow coolant into the pavement caused by steam. Honda permits driving the vehicle as long as the needle does not touch the red mark.