Ok so a few weeks ago I mentioned my 04 Discovery had a check engine light pop on and the temperature started to run warm. My commute from work to my house is 1 mile so I drove it home after work. Coolant was empty.

Refilled the coolant, husband scanned it and the codes came up as: P0455 and P0327 which he said was weird. Cleared em out and so far so good. He said I probably have a head gasket leak and to keep an eye on the coolant. Checked it today and the tank appeared to be empty. I had some left in the bottle from a few weeks ago and used that. It didn't take much but dang.

I guess my question is...where is it going? It isn't leaking out as far as I can tell but I guess it must be?

 

Codes you mentioned don't seem related to HG failure. Hopefully you are checking coolant level more frequently than every few weeks. If not it's likely going to the salvage yard soon.
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So is the loss of coolant common for these vehicles? Or is it related to the head gaskets or another issue I should check into?

I'm just not sure where to start on this one

 

D2's are not designed to consume coolant. Many vehicles do need to have small amounts of coolant added periodically. If coolant not checked on a regular weekly-monthly basis thing can get nasty.

The info you gave just says it got warm, reservoir was empty, refilled and now five weeks later reservoir empty again. Was the cooling system refilled properly or coolant just added?

I would start by checking visually for leaks Then refill the system and check the reservoir level each morning prior to first start. It's not unusual to get a small drop in coolant for several days after refilling. Just check and refill to full level when cold each day for about a week of use. Then continue to do daily checks, if you keep loosing fluid it will be time for a more though visual check and a pressure check.
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Mystery solved!! I've been keeping an eye on the coolant and finally drug myself under my car with my husband and saw where the coolant is going. It's leaking externally from the head gasket and I guess either evaporating or something which is why there isn't any wet spots.

Next project head gaskets.

 

If you are losing anti-freeze, you either have an external or internal leak. If a system is working correctly and has been bled properly, it shouldn't require additional fluid. As vehicles age, it is common to add a little extra fluid, but generally this is caused by hoses getting old and bulging (creating more volume area). But, if you are adding fluid ever other week...something is wrong.

Places to check externally...

First, visually check for fluid leaking underneath the vehicle. Then check under the hood, look at all of your hoses, radiator area, intake heater plate and just around the engine bay in general. One place that should get extra attention is along the bell-housing (where engine connects to trans). If the head gaskets or valley pan are leaking, fluid will run down the bell-housing and onto the hot exhaust and you'll never see it on the ground (unless it is a hefty leak). Look for staining on the exhaust pipe and converters (while cold), this will also be a clue of fluid dripping down from bell-housing area. Also, if you can smell anti-freeze (sweet smell) inside the cabin, when you turn on your heater, you may have a leak in your heater core.

Places to check internally...

Smell the exhaust, looking for that sweet smell again (just need to get semi close to the tailpipe, for a little whiff...nothing crazy...fumes can cause brain damage...I'm living proof of that). Also, check your oil and look for increases in fluid or milky substance on stick.

Good luck, hope it is nothing serious. However, be advised....head gaskets are very, very common problem on these vehicles...especially, if you have over 100K, use/used red anti-freeze, age of existing head gaskets or haven't changed your coolant regularly (every three or four years).

Brian.