Stop Koko Stop! / Brewster Makes Tracks

S4 E102: At the Chug‐a‐sonic Speed Track, Hanzo teaches Koko to control her new engine booster and she learns to brake at high‐speed.  Brewster discovers he has a good eye for track laying when he spots a buckled rail. / The Chuggineers are demolishing the old cooling tower, and Brewster can't wait to watch it come down. Suddenly, an urgent job comes in, and Brewster, knowing that he will have to miss the explosion, selflessly sets off to make the delivery. His good deed is rewarded when a problem with the detonator delays things, and Brewster gets back just in time.