Time: 45 min - 1 hr

Difficulty: moderate

Cost: $50-120 (higher end if tensioner is replaced at same time)

FUNCTION

Apart from providing power to the wheel, the engine's rotation is utilized to drive vehicle accessories such as the air conditioning, alternator, and water pump. These are all driven off the engine's crankshaft by means of a primary drive belt (serpentine belt) and A/C belt. 

WHY SERVICE

Drive belts are rubber and will break down with age and use. Cracks in the belt ribs will increase in number, and decrease in spacing. You may also get fraying along the edge of the belt. If not replaced, the belt could break leaving you without the ability to charge the battery or cool the engine. In short, you wouldn't make it far with a broken primary drive belt. Replace it before it leaves you inconveniently stranded. 

INTERVAL

Modern drive belts are extremely durable, but should be replaced every 60-100,000 miles. You might see a drive belt exceed 200k miles, but wear, extreme heat, and contamination make longer intervals a gamble. 

METHOD

Rotating the tensioner pulley arm to loosen the drive belt makes belt removal easy, but before you route the new belt you'll need to replace the A/C compressor belt. This belt can be cut or walked-off with a zip tie. You'll then need to use a zip tie or special tool to walk it back on. The belt is a "stretch" belt and meant to be installed in this manner. There is no tensioner pulley or slot used to adjust belt tension. Once the A/C belt is on, the primary drive belt can be route and installed. 

While the belts are off, spin the tensioner pulley and any idler pulleys by hand. If there is any drag or noise, now is a good time to replace them. 

The video below shows the replacement of both primary and A/C belts on a 2015-2024 era Ford F150 with the 3.5L EcoBoost.