Tools and Tool Box
Make simple tool shapes using flat pieces of cardboard. Lay a real tool on the cardboard and trace the shape. Cut out the shape, and paint it using bright colors. Label each shape on the back with the tool name. Make socket wrenches, lug wrenches and hammers. Place all of the pretend tools into a plastic tool box or a small cardboard box with two knotted rope handles on the top of two of the box's flaps.
Work Clothes
Make some simple mechanic's clothing. All you need is a pair of overalls and a white T-shirt. Smear on some black acrylic paint on various spots on the clothing. Let it dry thoroughly overnight. Once the paint dries, wash the clothes when needed in the washer, but keep them out of the dryer. The heat in the dryer cracks the paint, and makes it peel. Add a rag in the back pocket and a baseball cap as a finishing touch.
Tires
All mechanics need tires in their shop. Make several sets of tires using cardboard. Draw 16 different 13-inch circles on cardboard, and cut them out. Stack the circles in stacks of four. Glue each stack of four tires together using school glue. Draw a 6-inch circle in the center of the top and bottom of the glued stacks. Paint the center silver, so it looks like a hubcap. Paint the rest of the tire black. When you paint the cut areas on the outside, it looks like treads on a tire.
Engine
Create an engine using a medium size cardboard box. Glue on different boxes for the oil pan and the block. Spray paint the cardboard engine silver. Cut out spark plug shapes and carburetor shapes from cardboard, and attach them to the engine using hook and loop tape. Pop a few holes in the cardboard engine, and put some pieces of cut rope into the holes. This makes the spark plug wires.