Hissss, shussss, hissss. . .a ""funny noise"" in Mother's car occasions a visit to the service station, where the accommodating proprietor explains not only the power brake system where the trouble is located but everything else that Bill and Jenny want to know about cars. ""'Now we know what makes the engine run,' says Bill. 'But what makes the wheels go around?' 'Good question,'"" answers Bud and he's off on another illustrated minilecture. He even gets around to pollution before mechanic Marshall has the brakes fixed, and before the children fasten their seat belts and ride off waving, Jenny announces her intention of growing up to invent a non-polluting car. A routine though unquestionably effortless first glance under the hood.