Studies show that the chances of a serpentine drive belt failure rises dramatically after four years or 50,000 miles. Random cracks across the ribs are a sign of normal belt wear; they don’t mean the belt needs to be replaced immediately. Eventually, the belt will show multiple cracking with cracks spaced every 1/2” to 3/4” apart. If ignored, chunks between the cracks will break off. Always replace the belt when you find multiple cracks or missing chunks. Even if the belt only has random cracks, recommend a new belt to your customer. You may need a special serpentine belt tool, depending on the vehicle you’re working on.
Don’t forget to inspect the idler and tensioner at the same time. Check for rough bearings and damage or looseness at the tensioner.
Check the operation of the electric cooling fan as part of your cooling system regimen. On most cars, the fan should run when the coolant temperature reaches the threshold of the fan switch. The fan should also come on with the A/C when the vehicle is stopped or traveling at slow speeds. At higher speeds, usually above 25 mph, the powertrain control module turns the fan off because there’s adequate airflow through the radiator.
If the fan doesn’t work correctly, make sure the engine reaches normal operating temperature and that all electrical connections are secure throughout the fan circuit. Don’t forget the ground connections while you’re at it. Replace any bad parts.
Although electric cooling fans are the norm today, there are still a good number of rear-wheel-drive vehicles, like pick-ups and SUVs, on the road with mechanical fans. Many of these vehicles use a thermostatic clutch to control airflow efficiently while reducing engine load.
Fan clutch failures often go overlooked. An inoperative clutch can cause engine overheating and excessive high-side air conditioning pressures when the vehicle is idling or moving slow in traffic. A locked clutch hurts fuel economy and performance because of the high load on the engine.
With the engine off, inspect the clutch hub for signs of fluid leakage and grab the fan to see if you can turn it. If there’s fluid at the hub or the fan won’t turn, replace the clutch.
Checking fan clutch operation is easy. With the engine cool, cover the radiator to limit air movement through its fins. Start the engine, turn on the A/C and let the engine idle. The fan should turn slowly compared to the engine’s speed and churn little air.
After the engine runs for several minutes, you should hear the fan begin to roar as the clutch engages. Then, uncover the radiator and wait to see if the clutch disengages after the fan cools the radiator for several minutes. If the clutch doesn’t disengage after the engine cools or if the clutch doesn’t engage as engine temperature continues to climb, replace the clutch.
Proper cooling system service keeps your customers rolling, while building business for the shop. With customers keeping their cars longer than ever, opportunities abound.
Electric cooling fans became popular with the introduction of front-wheel-drive and the relentless goal of improving fuel economy.