The Constant Velocity (CV) joint boot encloses the constant velocity (CV) joint, a critical component of your front-wheel-drive car. The CV-joints are flexible couplings on each end (inner and outer) of the halfshafts. They allow the halfshafts to adjust to up-and-down and back-and-forth movements of the suspension and steering while simultaneously transmitting the engine's power to the front wheels. A CV-joint is more complex than a traditional universal joint as it must allow the wheels to turn smoothly under driving and braking loads. Because CV-joints are precision machined parts, they must be packed in lubricating grease and sealed from road grime in a protective rubber boot.
If a CV-boot tears, it will quickly let dirt enter the joint at the same time its grease is spun out onto the undercarriage and road. Thus contaminated, the under-lubricated joint will quickly wear and deteriorate. For this reason, the boots should be periodically inspected.
See Figures 1 and 2
The proper way to inspect CV-boots with the vehicle raised and supported on jackstands. Rotate the front wheels slowly one at a time while looking at and feeling the texture of the boots for cracks and tears.
This inspection should be performed every time the vehicle is raised for any kind of service (such as oil and filter changes). If a CV-boot has a tear or is starting to crack and look worn, replace it. In the case of an already torn boot, you will want to inspect the joint itself. For information on these procedures, see Drive Train , under CV-Joint and CV-Boot Removal & Installation.