Did I Overheat?
 

M.net question.

So this morning when driving, I turned on the heater and no heat came out. Got to my destination about 3 miles away, checked the radiator and reservoir and both were empty. The temp gauge stayed in the middle the whole time.
Never did the heater produce any heat during my drive.

Left destination after 4 hours, filled up the radiator w/ 2 quarts of water and drove home 3 miles w/ a working heater. (Like a jackass, I forgot my radiator cap and found water splashed on the underside of my hood).

Did I overheat my car driving to my destination since the heater was not working, although the temp gauge didn't indicate it?

wait, where did your coolant go if everything was empty? With no coolant in the system, I could definitely see the temp gauge not being of much use.

Today, I saw a constant drip from one of those hoses on the thermostat housing. Must have leaked out last night since I use my heater every morning.

ouch.

how is the car running now? any smoking or otherwise weird behavior?

I hope so

Working fine. I didn't check for smoking but I hope my headgasket is ok.

???

when my coolant was low due to a drain plug leak, here's what the gauge did:

warm up to 120 normally
jump from 120 to 170-180 (thermostat opening, gauge sensor on "cold" side)
during idle when car was hot and coolant finally circulated, jump to 230.

so gauges tend not to do much when they have nothing to measure. put some water in there quick.

Agreed, gauge requires something to measure. No liquid.. no measure. Hopefully it did not do permanent damage. Fill it up and closely monitor your coolant levels/any smoke for awhile.

How low does the coolant need to be in order for the heater not to produce heat? I have no idea how a heater works other than it transferring heat from the coolant.

the heater core is just a little radiator. it produces heat directly from the hot coolant. if you weren't getting any flow to the heater core, there won't be any heat.

So was it up to temp and then you drove it 3 miles originally or was it cold and you drove it 3 miles? It was only 2 quarts low, right? Was this 2 quarts to fill the radiator, or two quarts to fill the radiator + overflow tank full?

It should be fine. My truck did that. Just got low enough from a slow leak that the heater worked one day, didn't the next. Put a gallon in it (full size Dodge) and all was fine. Nary a problem since. If it was heating yesterday and not today it got JUST low enough, but you still had adequate water that you shouldn't have harmed anything.

It was like this back in the old days on my 70's vintage cars. We referred to the lack of heat as the "low coolant indicator". Top off and go about our business.

Yeah, I didn't explicitly say it but it should be fine. Especially if it was only 2 quarts low. The system holds a couple gallons. I can tell you that on my 99' (where the coolant temp sensor screws into the coolant housing that bolts to the back of the head) that if you run it low enough and leave it idling it will peg the gauge. :) I don't leave the car idling unattended anymore BTW.

I burst a heater hose and lost all the coolant from my system once. The gage went up a bit until the water was gone, then just sat there in the normal spot, just as others herte have described, and as expected. When this happened, I was stuck at a stop light and nowhere to go for several minutes. It probably ran for ~5-10 minutes with no fluid. I thought for sure that I blew the head gasket at a minimum. Well, several thousand miles later, the engine is still running with no smoke, no oil or coolant loss, and nothing odd besides slightly lower compression than before. These are pretty stout engines, I'd say. Or I got lucky.