Thank you for your timely responses and great information! Sounds like a steam cleaning is in order to me as I'm not sure we would be able to clean adequately ourselves. This info leads me to ask one more question though. Last year, on our way to NC, we were driving US 221 just south of Linville Falls. This is 7% grade, very twisting segment for about 4 mi. We had disconnected our toad, but the engine was warm. About 2 mi into this section the engine ran hot and the check engine came on (unfortunately there is no pull-off along here), so no choice but to continue. I was ahead of my husband in our toad and looked up in the rear view to see a big bellow of black smoke come out of the exhaust, but I was unaware he was running hot. Once we reached Linville Falls, we turned onto 183, which is a much better grade and road than continuing on 221, and the engine cooled immediately. At that time, we did not know about monitoring the RPMs or manually down-shifting (thought the auto would take care of that). Do you think this could have been caused by a dirty radiator, as we have not had a problem like this before along this route? It has not ran hot since, but we have not pulled a grade like this either.