Time to probe the hive-mind!
I took my 99 D2 in for an oil change yesterday; I usually do it myself, but its been raining for 2 weeks and my gravel driveway is basically mud. The guys at Jiffy lube said my coolant was out, almost nothing in the bottle. I usually top it off every couple weeks, bc the previous owner told me it evaporates (just another quark of this truck). The tech at jiffy lube said it was likely due to sediments in the radiator that are changing the evap temp of the coolant. There are not wet spots and no sweet smell so I am not thinking its a leak. I am at a bit of a loss with this one. Has anyone else had a similar issue? Is it as simple as a radiator flush to fix it?

 

Coolant does not evaporate out of the system. It is leaking either externally or internally. The previous owner lied to you. Also, never go to Jiffy Lube. First course of action should be to pressure test the system and report back....

 

 

I'd look at the throttle body heater. It can leak coolant and you wouldn't always smell the spill or see any drops.

 

I would be shocked if I was leaking into my engine. The engine had a large amount of work done to it about 10k miles ago (2014) including...> Cylinder Heads with New valves, Seats and Springs> Head Gaskets> Head and Manifold Gasket> Water Pump> Front Housing Cover Gasket> Timing Chains and Gears> Oil Pump

All new. I have no engine symptoms. Runs and idles great. No lack of power. I am somewhat stumped. BUT... I know it has to be going somewhere. Maybe it is internal... maybe it gnomes... I have no clue. Will get a pressure test done at some point. Anyone know how much a pressure test may run me at a shop?

 

2 weeks and expansion bottle empty is a lot of coolant, it is possible it is the the throttle body heater but you have to have a significant leak.

Try starting the disco and let it get to running temp then visually check for leaks. If it is the throttle body heater you will know right away, it leaks on the driver side valve cover.

If it is external you should see it somewhere - with luck.

 

It was more like 3 or 4 weeks and I believe the previous owner was adding water most of the time he topped it off. Thanks for the advice. I will take a look at it. I have started to check it every day just to track how fast I am losing coolant. I am adding straight 50/50 coolant now. So we will see what happens.

 

Ah that is a smaller leak but with any aluminum engine you need to keep the cooling system near to perfect.

I had a loose clamp on my throttle body heater so just a bit of loss over 400+ km maybe an 8th of the tank. Getting the engine warmed up let me see the wet spot and sort it out.

 

Update!

The loss of coolant has nearly stopped since topping the tank off a few times with 50/50 coolant instead of straight water. I am guessing the system has just been purging the water vapor overtime which explains the fact that I had no visible coolant leak. Still going to monitor it... disco's only stop leaking when they are empty! haha.

 

I recently had some hoses replaced (inlcluding the top hose w/ the bleeder valve and the throttle body heater tube) on my Disco II at a reputable shop. They told me they did a pressure test and all was fine but i've been losing about an inch or so of coolant level in the expansion tank every few weeks since. I haven't noticed any signs of leaking however since it came back from the shop. I'm adding 50/50 mixture. After reading this thread i'll have to check the throttle body for signs of leakage.