[Kevin in NJ]

You can clean the water jacket with pointy things and wires.

Work at it for a while and get all the scale off the walls as that will insulate the heat transfer to the water.

I worked for a while. I flipped the block upside down to help get rid of the junk as well as (after the big stuff came out) blowing and vacuuming. A stiff wire is use to get around the corners.

You will be amazed at how much will come out of the water jacket.