Engine overheat and cool air -thermostat?

You have a fluid leak someplace.

The fluid has now dropped low enough that the pump isn't picking it up and sending it to the heater core or the heater core has become air locked and the head is airlocked cooking the valve seals to hard clay for you. The temp gauge is usually in the head. If you continue driving it like that, it will become an oil burner at best and at worst the engine will seize up.

You need to open the rad up and get fluid in it first, then start looking close for leaks. If there are no visible external leaks, you then need to address a blown head gasket or maybe intake gasket depending on the engine.

Mike

But you didn't check the coolant level?

And still didn't check the coolant level?

Did you EVER check the coolant level during all this? My guess is that you've been slowly losing coolant and operating with a partly empty system, and now its gotten low enough to be catastrophic.

Why? the car has done nothing but OVER heat. The fact that you didn't get heat out of the heater is because it was dry, not because the engine was cold.

What kind of car? Most of them are two little bolts, a hose, a gasket scraper, new gasket, and half an hour. Some (mostly Japanese imports) practically require removing the engine.

Thanks for the check the coolant comment.

So it seems there is a leak or at least no antifreeze to see in the rad and little to none in the overflow. The oil is not milky and the antifreeze overflow ( what little there is) does not seem contaminated either. Water pump seems fine (no noise, no visible leak, no movement of pulley), now the question of finding the leak and I have still not ruled out head gasket --can you lose that much antifreeze via exhaust?? I have noticed some white exhaust but it is cold presently and I see many cars with similar white exhaust.

For the moment, I am going to top up the existing fluid with a economy antifreeze 50/50 mix with distilled water with the intent of flushing the system once I figure out where the leak is. Of course, there is no pool of fluid under the vehicle which is good and bad.

The responses have been very helpful and if anyway would like to offer suggestions for the next step, it would be greatly appreciated.

What flavor of vehicle and engine is it?

Mike

You can easily lose that much antifreeze over a period of weeks simply by having a radiator cap that doesn't quite hold enough pressure! Each time you run the engine, the leaky rad cap bleeds off coolant vapor rather than preventing the coolant from turning to vapor. Over time you get an empty radiator.

The real question here is whether you now have serious damage due to continuing to drive it with air/steam pockets in the cooling system which can cause severe local overheating, especially in the cylinder head which is the part most prone to damage from overheating.

Well the first thing to do is re-fill it with coolant making sure to thoroughly bleed all air out of the system, take it for a short test hop (or just run in the driveway) and see if the overheating returns. If it doesn't, then keep a hawk-eye on the coolant level for the next few weeks, while also being very careful to observe possible leaks. Don't forget that you could have a leak in the heater core, which might just dump the coolant out along with any A/C condensate, thus disguising it somewaht. I'd replace the radiator cap on general principle- they're cheap.

If you're lucky, it'll be just fine.

To pressure test or not:

I emailed a pretty big Radiator garage about a pressure test and this is what they said; "The best we can offer to you at the present time is

to bring your vehicle in this Saturday and we will pressure test your system for free and hopefully find out where your coolant is going. More than likely, if you have never noticed any coolant on the ground (leaks) your vehicle probably has a intake or head gasket leak."

It is free, I am inclined to do it this Saturday morning and let the chips fall where they may. My thinking is usually, if it ain't broke, but it is broke, so may as well go for it.