I have an 02 Disco that is presenting an odd problem to me. After being away for the weekend, I picked up my disco and before driving off I noticed the expansion tank was almost empty. When I was parked Friday night it was full. I've made a habit of checking the coolant level almost daily due to the horror stories we all see daily. I've got no leaks externally. No coolant in the oil. No boiling. No overheating issues. None of the classic signs of hg failure. I performed 3 block tests which all showed no leaks (chemically). Anyone else had similar symptoms?

 

Either a massive air pocket got eliminated, you have a leak, or your consuming coolant.

I'd start with an HC (hydrocarbon) test on the coolant, and go from there.

 

hmph... a disco from a parallel universe (the real ones, not some silly sci-fi thingy), desperately in need of coolant, hopped across the multiverse and took some of yours while you were not looking, nor expecting it.

or...

what racerx said.

 

I did the HC test with negative or in this case, positive results. There was little to no color change. I guess the next step will be compression testing as there is no external leak. As for this parallel universe rover, let me catch him taking my coolant.

 

You don't mention a pressure test of the cooling system being done but you do know there are no leaks?

 

Unfortunately I don't have access to one at the moment. I plan on having it tested at a shop within the next two days. I jumped the gun on being 100 % sure it is not leaking. If it is losing coolant and not showing the obvious signs of a hg issue it has to be going somewhere though.

 

...and that would be the Mars Rover and I wouldn't want to mess with him

 

I'm sorry to say this is may be a symptom of a blown head gasket. If the front or rear of the gasket blows, it will leak coolant but the coolant won't get into the oil or vice versa.

Lay underneath with a flashlight and examine the front and rear of the heads. I bet you'll see a trail of coagulated coolant (especially if you are still running dexcool).

 

Surely something would show up on the ground? The entire expansion tank is empty..not saying it couldn't coagulate but seems like there would be something getting wet below. To the OP, are you parked on pavement or gravel? When mine went (and I had dexcool) I had a nice puddle on the ground and there was no way you could miss it. It was leaking in the rear of the gasket.

 

Uv dye additive is an optional helper, too