Taking a break from my SAI travails and looking into a coolant leak. My 2004 Disco II goes through coolant quite rapidly, but I don't see evidence of that big a leak. I never see any puddles/drips on the ground under the engine anywhere, but the reservoir will drop a couple inches in the reservoir within a couple hours' drive. There is a slight dampness visible in the head gasket on the passenger side but not enough to indicate that amount of fluid loss. When I changed the oil a few months ago, I did notice a lot of shiny/wet area around the front passenger part of the engine but at the time thought it was just a result of my sloppy first time changing the oil and getting the oil everywhere in the process (I'm sure there's a less messy way to do this). I don't really smell a coolant odor after running the car, don't see any obvious spraying, oozing or dripping with the engine running, and sometimes it seems the coolant is disappearing even without the engine running (but still not dripping anywhere that it actually makes it to the ground). I've read there's a common leak area under the throttle body for leaks on the driver's side. Any common leak areas on the passenger side toward the front that wouldn't leave a lot of evidence?

 

Heater Core, Heater hose connection at the bulkhead, radiator, water pump, front timing cover, throttle body heater plate, crack in the reservoir, and yep the HG's. Personally I think you need to rent or get a hold of a pressure test kit, put 16-18PSI on it and look for leaks.

 

I'll see if I can get hold of a pressure test kit.

 

Also try replacing the filler cap. When they go bad they can cause leaks out of the overflow.

 

Secure a plastic water bottle on the overflow tube off near the reservoir. If the cap is not holding pressure, there will be coolant in the bottle

 

My 03 had some disappearing coolant without any obvious issue. Seemed to be two things.

Expansion tank cap and expansion tank.

I replaced the cap and that reduced the loss of coolant. Next up the level in the tank seemed to drop to a specific level and stay there. Replaced the tank and no more coolant loss. Gonna guess there was a failure in the original tank seam.

These where not huge coolant losses but enough I noticed and wanted to sort out.

 

You could be losing coolant in the combustion process due to a small crack in one of the cylinder bores. Not enough for you to notice white smoke from the tailpipe or smell it. Worst case scenario, but worth mentioning. If you can't track down any obvious leaks check the spark plugs for discoloration isolated to one particular plug to narrow down that possibility.

 

After a lengthy break dealing with other issues, I'm back to trying to figure out where I'm losing the coolant. I do see moisture along the head gaskets on both sides so I'm sure those will eventually need to be replaced, but I have neither the time, $, nor facilities to tackle that before I put it up for sale. I also now (within the last month) see a small wet spot on the driveway under the throttle body heater and when I had the hood popped to unhook the battery while I replaced the passenger compartment fuse box), I noticed some drops pooling at the bottom of the TBH. However, the size of the little puddle--about 2" in diameter--doesn't seem to account for the amount of coolant I'm losing even with the engine not running? Or does it evaporate that quickly... That is the only place I'm getting any puddling on the ground.
Do I replace just the throttle body heater gasket or the whole heater?
Any idea where else I might be losing coolant? Seems to lose the same amount over time regardless of whether or not the engine is running--about 1/4 of the reservoir per week or so.
And, no, I haven't had a chance to get the system pressure checked, but so far just normal atmospheric pressure seems to be plenty to keep it leaking!

 

A throttle body heater kit comes with all the parts you need to fix the leak. There's a gasket as well as the heater plate itself.
Did you replace the cap on the coolant reservoir, or the reservoir itself?

 

Check...............Your..................Sump