A few weeks ago, the climate control system in my 2002 Disco II (~105,000 miles) started alternating between hot and cold air. I checked the coolant and it was a bit low (just to the bottom of the overflow reservoir). I checked the oil and topped the system off with coolant - the truck was fine for about two weeks (~700 miles). A few times in that two weeks I noticed a coolant smell when I turned off the truck. On Tuesday night (just after the very cold temps had hit Wisconsin) I was driving friends home and on my way back, the floor vents started alternating cold and warm air again. I was nowhere near anywhere that had coolant available at that time of night and my temp gauge was reading fine. Less than a mile from my house, the temp gauge crept up and the red light lit as I was in my neighborhood. There wasn't any coolant in the overflow bottle - it took about 1/2 a gallon to top it off.

Now, I've searched and read up a bit on coolant troubles and head gasket jobs, but I'm still a bit baffled by this one. Here are the symptoms:
[ul][*] Coolant is leaking to somewhere (clearly)[*]Occasional sweet smell of the exhaust[*]No puddles of any fluid under the truck when parked overnight[*]I haven't seen coolant on or around components in the engine bay anywhere[*]Oil looks fine (very dark brown), although it is about time for an oil change[*]No seepage around the head gaskets[*]Truck runs great, no CEL light at all.[*]The transmission temp light came on for less than 15 seconds the morning after the overheating incident
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Right now, I'm suspecting head gaskets. Here are my questions:
[ul][*]I've ready plenty about the cylinder liner dropping, but if I had that issue, wouldn't my oil be milky in color considering the coolant loss? [*]Is there any way to test for a cylinder liner having dropped?[*]Would a compression test indicate whether my head gaskets were bad?[*]What color would the spark plugs be if the engine is burning coolant?
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The holiday season is probably the worst time for this problem to happen. If it is indeed head gaskets, it looks like a job I'd be attempting myself though I've never done such a thing before (I am pretty handy with a wrench and have access to a heated garage). Do you guys have any tips for anything else it could be?

 

I just had the same issue, minus the climate control system issue. It ended up being a cracked coolant reservior. Just replaced it and its been good since then. As the engine heated up the crack expanded just enough for the cooland to leak out, as it cooled the crack sealed so I never had puddle. I also was hearing a steam sounds when I was having the problem, which I later found was the coolant dripping on hot metal, hence burning it up before it puddeled up. This may not be your issue, but its a good place to start.

 

Open your oil filler cap, is the inside top of it milky white?
Pull the oil dipstick, is it milky white?
Whitht eh truck running do you have a sweet smell around the tailpipe?
If you have any of those then look for a blown headgasket.

Look under the throttlebody for coolant ontop of the engine, also feel around for a slimy goo.
If you find that then your trottle body preheater is leaking, very easy DIY $5 fix.

If, and that is a big if, you had a dropped cyclinder liner you would know it, either it wouldnt run or it would sound like a really bad rod knock.

Check the throttle body pre heater first, very common on DII's.

 

this really sounds like a sleeve,pull the plugs and look at the color it will be apparent on one plug, a sleeve is a sneaky thing sometimes and sometimes not scott
but before you panic look for dried orange juice as explained above

 

Just go for a coolant pressure test to verify your leak. I would suppect the head gasket since you smell coolant at the exhaust.
Don't waste a lot of time with this or you may toast your engine one day.

 

No milky discharge anywhere to be seen.

I did drive it again today (making sure the coolant was full before I left, and checked it again afterwards), and I noticed that I could smell it from inside the truck. I can't smell very well since breaking my nose, but I was able to smell it more from the engine bay rather than the exhaust. I'll go after it tomorrow and see if I can pinpoint where it's coming from. If I'm not successful, I'll have a the coolant pressure test done on Monday.

 

Sounds like a plan.
Because you can smell it inside the cabin the I would look for the throttle body heater leaking.

 

throttle body yes head gaskets no, only 4 cylinders on the head can burn coolant all on the ends front and back. Head cracked rarely but gasket i never seen this on the bosch motors becuase the last place a head warps up is on the coolest parts of the heads scott