I've got a crackling / snapping sound coming from my heater
core. If I pinch off one of the heater hoses, the noise stops. The noise comes
on acceleration, and at a slight rev in neutral. Causes I can think of :
1) Steam is forming somehow in the cooling system, and I am hearing the
old-fashioned steam radiator sound in the heater core. 2) Air bubbles are
trapped in the heater core and are slapping around in there. 3) A piece of
debris (metal) is flopping around in the htr core.
Additional info : I do have a coolant leak at the rear of the intake manifold.
Maybe air is getting into the system there.
The car is an 85 Chevy Caprice. The heater core is only 3 years old.
Any ideas ?