Originally Posted by Jas0n
I checked the coolant level and it seems I was down a significant amount (a less than a gallon). Topped it off and now I have heat! But how did the system lose so much - I don't see any leaks. Evaporation when the thermostat wasn't opening?
So you had the volume low enough that the heater core was full of air with only a small amount of coolant circulating through it if any at all.
In order for coolant to leave a semi sealed cooling system, coolant is leaking or being consumed into the engine.
As suggested by Jason, the head gasket could be leaking or a common issue with the aluminum V8 are dropping sleeves.
The land Rover V8 design is atrocious.
The factory punched a bore straight through the cylinders and pressed in sleeves held by locktight.
The first time the engine overheats, the sleeves often drop and the engine is finished.
All the factory had to do was leave a 1/4" lip at the bottom of the cylinder to prevent the sleeve from dropping.
The head would hold it down and the bottom lip would hold it up.
But no they punched it all the way through yielding a V8 that rarely survives an overheating.
When the head gaskets go or the sleeves drop, the coolant often becomes pressurized by engine compression that forces the coolant out.
After enough coolant is forced out, the engine hasn't enough to cool it and will overheat.
Overheating causes the sleeves to drop and the downward spiral continues until it lets you down.
I hope this is not your case.
For me, this is the reason we try not to run any V8 engines.