No it does not mean head gaskets.
It cold be almost anything, a leaky radiator, leaky hose clamp, leaky throttle body heater...could be almost anything.
Could be a rusted out freeze plug too, have them check those, there are 4, 2 on each side of the engine.

 

Ok, well this is crazy. I took it down, and they tested the entire cooling system twice, let the car run for a while (more than a half hour I'd say), and visually inspected almost everything I can think of, and they found no leaks or broken seals. What's crazy is that it hasn't leaked since, and besides the increase in sound from the A/C, everything seems completely fine. One of the mechanics even said that my A/C fan seems perfectly ok to him and that it was spinning normally (which makes me wonder if whatever occurred actually made my A/C fan run normally and it was previously running underpowered, but that makes no sense to me either).

One thing he did say, and something I had been thinking about, is that when he initially went to take off the coolant cap, the cap wasn't secured that tightly. Is it possible maybe that in checking my fluid levels one weekend I didn't tighten it fully? I do notice that there seems to be a little bit of coolant residue on the outside of the reservoir tank. I don't know what would make so much of it come out like that though, or how the cap would still have been on as it was when I first popped the hood.

As for my A/C in general, he said he believews it could possibly be the compressor causing intermittent surges, but I don't think that has anything to do with the coolant spill that just occurred. I'll keep you all posted, pretty interesting problem to just disappear.

 

If your AC tried to lock up it might make engine overheat?

What is your temp guage showing? I know they are not accurate but better than nothing?

Take it to the LR Stealership and see what they tell you?

 

Strange. It could have just been one of those odd things where the stars aligned, and a combination of a loose cap, pressurized cooling system and engaging A/C compressor just as you killed the motor (consequently stopping the water pump) caused a spike in pressure and fluid spill. Who the heck knows? But I do know that on my truck, I have some heat shield on the inside bottom of the hood, and there is an indentation on it from where the coolant reservoir cap presses on it. So a closed hood just may have kept a loose cap on.
For peace of mind, you might consider getting a new cap. It's about $12, and it removes a variable in the equation. But overall, as long the system is not leaking or the engine overheating...just go with it.
As for the A/C and RPM's, I can't say for sure about our Rovers, but I remember that on my Jeep the A/C control circuitry was set up so that when the A/C was on, it bumped up the RPM's by 100 or 200 (noticeable at idle), to compensate for the work required by the compressor. Like I said, I don't know if this how our Rovers are set up, but if it is, it's possible that the signal there is intermittent. Just a thought.
Or like Danny said, perhaps your compressor is getting close to locking up for whatever reason, and providing some extra resistance. Maybe just run it with the A/C on and the hood open, and watch that compressor really carefully, and see how it acts when the clutch engages.

 

Do not mix Dex Cool with the green (ethylene glycol) coolant. That will surely compound your problems. I always use the green stuff in my '96. I'm not sure what year they switched over, but I've always been told not to mix the green with the orange.

 

I have just modified the bottom coolant hose for the coolant temperature sender for the electric fan conversion and (here's my point) I tested the system for leaks by removing the plastic filler plug on top of the rad and treaded in brass adaptors to take a tire valve fitting. Using the air compressor I preassurized the system to 11 psi (that's the max it can take) and listened for leaks (the system was drained to modify the hose for the sensor). Air escapes better than liquid.
For the tire valve adaptor: get any tire valve, strip off all rubber any way you like it (it must be clean), solder it to a suitable brass adaptor that fits into the filler hole BUT remove the stem or it will be damaged by heat. Reinstall the valve stem , Done.
Remember: 11 psi max!
This is a neat trick to test the coolant system for leaks, found the water pump seals leaking.
I think that A) there is a failure in one of the joints in the lower rad hose ( I mean the joints for the coolant reservoir or the cabin heater core) or B) the green liquid under the disco isn't yours (probabily a Toyota that was parked there before you) and the A/C behaviour is just a coincidence. and the gushing sound is from the Toyota owner crapping his pants finding out he blew the heads.
The RPM surging and dropping with A/C: I think the A/C bypass valve is sticking. Do a complete throttle body cleaning with either carb cleaner or SeaFoam.

SD

 

I know I am late to the party but there is a product out there called A/C dye. Used to find leaks. It is bright green in color and can sometimes be mistaken for coolant. Just a thought.