Understanding the CV boots in your car

Thursday July 12 2018

Understanding CV boots your car

When CV axles are worn out, the joints will become loose and click when turning. COURTESY PHOTO 

By David S Mukooza

A number of drivers think understanding car parts is the work of a mechanic. However, acquainting yourself with some easy to replace parts saves you money and probably being cheated by unprofessional mechanics. Found in all front-wheel-drive and many rear-wheel-drive cars, constant velocity joints (CV joints), commonly known to drivers as rubber boots, transfer torque from the drive shaft to the wheels and permit the vehicle suspension system to move up and down without the passengers noticing each bump.

According to Ronald Lubega of Grace Lubega Motors in Makerere, the purpose of CV boots is to retain the grease in the constant velocity joint or in the active car joints and to prevent contamination of the grease by road debris or dust and chemicals as you drive. He encourages drivers to replace the damaged boots immediately because failure to do so results in having to pay considerably more money to replace the CV joint/driveshaft.

“It is important that you check your boots on a regular basis. Drivers should also have the complete driveshaft removed and serviced every 40,000 to 60,000 kilometres as this will save you money in the long run,” he says adding that the grease loses its viscosity and lubricating qualities after covering these distances, so replacing it extends the lifespan of the CV joint and the boot as well. Lubega says common signs of faulty CV jints include grease leaking onto the inside of the wheels, vibrations around the CV axle and clicking noises during turns.

Constant velocity axles, commonly referred to as CV axles, are the component which transfers the power from the transmission to the wheels to propel the vehicle forward. They have a flexible constant velocity joint which allows the axle to flex in a variety of ways in order to allow wheel movement created during turns and when the suspension travels.

This flexible joint is covered in a rubber boot that is referred to as the CV Boot. This boot serves as a simple dust cover for the CV joint meant to keep out dust and dirt, and keep in the grease that lubricates the CV joint. When a CV axle boot goes out, it opens up the potential for the CV joint to become damaged by contamination. Usually a problematic CV boot will produce a few symptoms that can notify the driver that attention may be required.

Grease leak
Ronald says a grease leak is the first symptom that is most commonly associated with a bad or failing CV boot. Over time, with exposure to the elements a CV boot can become dry and then crack or tear. When a CV boot cracks or tears it will usually leak grease onto the inside of the wheel. Often times the grease can also be thrown forcefully onto the chassis or other parts on the underside of the vehicle as the CV axle turns. A torn boot can also allow dirt, debris, and moisture to enter the CV joint, which will damage the joint.

According to Lubega, another symptom of a bad CV boot are vibrations coming from the CV axle. The vibrations may be a result of moisture or debris getting into the CV joint and causing damage. Usually a vibrating CV axle will need to be replaced.

Clicking noise during turns
Lubega says another more serious symptom of a potentially torn CV boot are clicking noises from the axle during turns. This is a symptom that the CV joint has become loose, causing it to click during turns and this might have been common to many drivers. A clicking CV joint will need to be replaced, as most CV joints are usually not serviceable.

Be vigilant
Bosco Kigongo of Icony Garage, says CV boots serve a simple but important purpose and allow the CV axles and joints to stay clean and enjoy a long service life. He advises that if you notice or suspect that your CV boot may be damaged, have a professional technician inspect the vehicle to determine if a CV boot replacement is appropriate, or if the entire CV joint should be replaced. However, he says, in most cases if the noise is very intense then the entire CV joint will need to be replaced.

Guard against further damage

It is possible to drive a car with a torn CV boot, but doing so will likely lead to further damage that will eventually require more extensive repair. Bosco Kigongo, a mechanic at Icony Garage, says CV joints are covered by rubber or plastic boots known as a CV boot or drive axle boot, which are responsible for keeping the joints lubricated and preventing dirt and water from getting in.

Unfortunately, this is a part that sometimes fails. If a CV boot tears, grease can leak out and moisture and dirt can get in. He adds that if left unattended to, it is only a matter of time before the joint fails from lack of lubrication or corrosion. When that happens, the whole axle may need to be replaced.

Kigongo also notifies drivers that outer boots and these are the ones closest to a wheel are more prone to tears than inner boots. One indication of a torn boot is grease spots under the front axle or grease splattered on or around the inward-facing side of a wheel.

According to Kigongo CV axle boots often last the life of a vehicle and many people do not list them among items that need periodic replacement as part of the vehicle maintenance. Drivers should inspect them at least once a year or more often on high mileage vehicles or the ones such as off road use vehicles.

Kigongo says replacement cost depends on the car but small SUVs use rubber boots that can cost from Shs30,000 and he says this depends on the place you are buying from. However on the cost of labour for replacement he says this depends entirely on the relationship between the driver and the mechanic but adds that the price should be friendly.