On my 216 the water used to only drip out of the petcock. Even after I removed the petcock and jiggled with both a wire and nylon brush it would only run very slowly. On this site I read about using Evaporust. I filled the block with Evaporust and let it sit for 2-3 days, it dribbled out, not much better...I used the wire in the petcock hole again and also used a shop vac nozzel on the petcock hole. The 2nd time I did the same and then the Evaporust ran a bit more freely...but not my much. The 3rd time doing the same steps, the shop vac did the trick and the Evaporust gushed out. It just took a lot of time for the product to work.