Mike:

Have you replaced your radiator cap (its on the coolant tank)? If not, it may be bad, and allowing the coolant to spill out of the recovery tank under the fender behind the front wheel.

My heater gurgles once in a while too, very annoying. I've not replaced the cap on the 300D yet, but did replace the one on the 300TE last spring due to coolant loss -- boiled over some when hot, especially if just pulling off the highway. New cap fixed it.

Another other thing to check is the circulation pump up by the battery -- it can both go bad and leak, and leakage won't show up in the engine compartment.

The water pump can "weep" very slow when the seals first go, and will, I think, drip straight on the ground, not into the pan. Hard to see until it gets bad.

Let us know what you find -- my 300D is also slowly consuming coolant, and I fear a cylinder head gasket is in my future. I'd much rather it be a water pump!

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!