Hose connections will rot, and a strip of rubber may peel off the inside and be drawn across the passage; or if dirty water is used, the dirt may choke the fine radiator passages or other channels. If the radiator is covered with mud, air cannot get at the tubes to take the heat from the water that they contain. A very usual cause of overheating is a slipping fan belt; an adjustment is provided by which the belt can be tightened when it works loose. ENGINE SMOKES Black smoke indicates that the mixture is too rich; blue smoke is a sign of too plentiful lubrication. Oil that is too thin, or that is of a poor grade, will cause smoking; good quality oil of the grade recommended by the manufacturer should always be used. Broken piston rings, or rings stuck in their grooves, will be the cause of smoking because they will permit an excess of oil to pass by them. CHAPTER XIV CAUSES OF TROUBLE Engine will not start. No mixture. No ignition. No compression. Engine starts, Clogged fuel pipe or strainer. but will not Air-bound tank or carburetor. continue running. Clogged exhaust. Wet spark plugs. Governor out of adjustment. Engine loses power. Retarded spark. Poor compression. Overheating. Clogged exhaust. Incorrect mixture. Governor out of adjustment. Tight bearings. Dragging brake. Slipping clutch. Overloaded. Engine stops suddenly. Ignition trouble. Engine slows down Clogged fuel supply. and stops. Incorrect mixture. Overheated. Regular miss in one cylinder. Defective spark plug or wire. Irregular miss in all Sticking contact breaker. cylinders. Defective distributor. Clogged fuel line. Irregular fuel feed. Water in fuel. Faulty ignition connections. Engine runs unevenly. Incorrect spark plug gap. Incorrect mixture. Binding carburetor float. Sticking valves. Sticking governor. Engine overheats. Spark retarded. Faulty cooling. Faulty lubrication.