Cooling system leaks become more notable during A/C operation because.
#1. Condenser heat transfer to radiator.
#2. Engine load.
#3. Reduced radiator heat rejection capacity = Lime buildup, corrosion or material breakdown from age.
#4. Bad thermostat.
#5. failing water pump.

Added heat = added pressure = weak points fail = a damp spot becomes a stream or spray.

Best advice:
#A. Replace the thermostat.
#B. Flush the cooling system.
#C. Disconnect, clean the leaking hose end and fitting, reconnect.
#D. Clean any trash from between radiator and condenser.
#F. Clean trash from under electric cooling fan, may need to remove fan for this.

__________________
ASE Master Mechanic

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D

https://www.boldegoist.com/