I have an electric baseboard heater that makes a clicking noise. The noise starts several minutes after I turn the heater on, and stops as soon as I turn the heat off.

I opened the screw/plug at the end of the top pipe. Some water came out. The noise continues.

Advice? Thanks

Electric baseboards don't have water, unless you mean the boiler is electric. Sounds like you have hot water heat. You may have to bleed the register for a while longer to get all the air out. That's a good place to start.