BMW E38 coolant loss
Where does an E38 usually leak coolant from?
Common leak points are the thermostat housing, the expansion tank, the water pump (base of the shaft), the plastic end tanks of the radiator, the hoses and the heater core. The thermostat housing and the tanks can have a hairline crack that leaks only under pressure.
Why does coolant disappear when no leak is visible?
A hot engine evaporates a small leak, so no stain is left under the car. Look in the engine bay for white, dried residues. On the M60 and M62 the leak can be in the plate under the intake manifold (valley pan). Clear water dripping from the middle of the car is usually normal air conditioning condensation.
Can coolant disappear into the engine?
Yes. A blown head gasket consumes coolant and raises temperatures without any external leak. On the M67 diesel the oil condenser is under the intake manifold, and a leak in its seal lets oil into the coolant. Check the condenser before taking the heads off.