Serpentine belt, pulley and tensioner replacement in Kansas City, Kansas

Open the hood on most cars and you will see a long ribbed belt wound around several round pulleys at the front or side of the engine. That is the serpentine belt. The crankshaft turns it, and it turns the alternator, the air conditioning compressor and, on many cars, the power steering and the water pump.

Two other parts keep it working. Idler pulleys guide the belt along its path. The tensioner is a spring-loaded arm with its own pulley that presses on the belt and keeps it tight. Each pulley spins on a bearing, and those bearings wear out too.

A squeal on a cold start, or a chirp when you turn the wheel or turn on the AC, is the classic belt noise. It usually means the belt is worn, glazed or not being held tight enough. A growl, grind or rattle that sticks around is more often a pulley or tensioner bearing on its way out.

Buying a belt for a bad bearing doesn't fix much, and the new belt can wear out fast on a pulley that wobbles. Josh checks the belt, spins the pulleys by hand with the belt off, and watches the tensioner run before he says which part is the problem.

Your owner's manual lists when the belt should be checked or replaced. In between, a quick look with the engine off tells you a lot. If oil is getting on the belt, the leak is often a gasket, and fixing only the belt means the new one gets soaked too.

• Cracks across the ribs of the belt, chunks missing or frayed edges
• A shiny, glazed look on the belt where it rides on the pulleys
• A tensioner arm that bounces or jumps around with the engine running
• A pulley that wobbles or sits crooked
• Belt dust around the pulleys, or the belt riding off the edge of a pulley
• Oil or coolant on the belt, which makes it slip and points to a leak that needs fixing too

Often the only warning is the squeal you may have been hearing for weeks. What you lose when it goes depends on what the belt was turning on your car.

• The battery light comes on because the alternator stopped charging, and the car runs on battery until it dies
• Steering gets heavy on cars where the belt drives the power steering
• The air conditioning quits
• On engines where the belt turns the water pump, the temperature starts to climb

Watch the temperature gauge more than anything else. If the belt breaks and the gauge starts climbing, pull over and shut the engine off. Driving an engine hot can warp the head and blow a head gasket. Then call or text Josh before you drive it any farther.

Kansas City swings from hot summers to bitter cold, and both are hard on rubber. A belt that has been squealing all fall is more likely to crack on the first cold morning. And a timing belt, if your engine has one, is a separate part and a separate job, covered on its own page.