Understanding Automotive Brake Parts and Services

How To Adjust A Vehicle Drive Belt

If your vehicle squeaks at the front, or the power steering and A/C fails, the drive belt, or serpentine belt, could be the culprit. The serpentine belt is a central component of the engine system providing power to the air conditioner, engine, alternator, and power steering.

Some belt are self-adjusting, while others must be manually adjusted. Here are tips to adjust a drive belt.

Prepare to Work

You will need work gloves, socket and wrench set, flashlight, and measuring tape. Turn off the engine, and let it cool.

Prop the hood, and locate the battery, which is commonly a large black box with wires. Loosen the nut on the ground cable that secures the negative battery wire with a wrench, and remove the wire. Negative wires should have a minus sign on the terminal. Leave the positive wire in place.

Test the Tension

Locate the drive belt, which should be easy to identify. Some vehicles may have a two-belt system, so refer to your owner's manual. 

Check the belt for sagging. However, tension can be low even when no visible sagging is present. Belts that have a glossy look should be replaced.

Locate the longest stretch of the belt to get exact results. Use a ruler or measuring tape to find the center point on the longest stretch. 

Press the center point on the belt with your thumb, and measure how far the belt moves. You can also buy a commercial belt tension gauge. Also, watch for any movement in the tension pulley in modern vehicles. The pulley should not move when the belt moves.

 If the belt moves more than one inch, it is too loose. Each manufacturer has different recommendations for belt tension.

Adjust the Tension

Locate the drive belt pivot point bolt that is commonly opposite to the bolt on the alternator. Loosen the bolt with a wrench, but do not remove it.. 

Find the adjustment screw, which is a wing-shaped nut near the alternator. If the belt has no screw, it is likely an auto-adjust belt. 

Attach the socket end of the socket wrench on the nut, and rotate it to the right to tighten. Ensure the belt is secured  on the grooves of each pulley.

Test the tension with your thumb, as you did previously. It should be at the recommended play for your model. Keep adjusting the nut as needed. Tighten the pivot point bolt after you get the right tension.

Reconnect the battery wire, start the engine, and listen for squealing. If you don't trust your skill, the tension pulley moves, or the same problems still persist, consult a mechanic like Oak Hollow Tire Car Care Center Inc.