Your drive axle constant velocity joint boots stop dirt and water from getting into your constant velocity joints, and keep the lubricating grease from getting out, but they can and do fail. So how do you check if they’re in good health?
The CV boots are nothing more than little rubber accordions that go ever the CV joints on your drive axles on front and all-wheel-drive vehicles. They’re a $5 part at best, but don’t let their low cost fool you, if one goes bad it can mean a big repair bill.
Under each CV boot is, one at the transaxle end and one at the wheel, is a constant velocity joint. Without the boot, these grease-laden joints would become thick with dirt and filth and lose their ability to flex and rotate.
If you hear a clicking noise that is especially pronounced when tuning a corner, chances are a CV joint has already gone bad. In extreme cases, if left to its own devices, the CV joint can fall apart scattering ball bearings and pieces all over the road. When this happens, you are left stranded with a car that runs but won't move under its own power.
- Get Jacked - You’re not going to get decent access to the CV joints while the car is on the ground, so get it jacked up and supported on jack stands. Once up, take the front wheels off, this should give you decent access to the drive axles and CV joints.
- Spring Clean - The inner fender and front suspension are probably going to be thick with road dirt and filth. You can’t properly inspect anything in that, so give it a wash. Don't worry too much about getting the brakes wet, but try not to get soap on the discs.
- Lock it up - For the outer CV joint boots, turn the steering wheel full lock. This will give you access to get your head behind the wheel hub where you’ll be able to better see the CV joint.
- Tied Up - The CV joint boots are held in place by circular clips, either metal or plastic. Check these first. If they’re present, correct and tight that’s good. If they’re missing or just a zip tie, you may well have dirt within the CV boot, or a lack of grease. Replace a missing tie asap, but not before pulling the CV joint back from the wide end to check that there’s nothing in there but grease.
- What’s in the ’box? - At the inner, transaxle end, check for any signs of grease leaking out. Again, check the ties and that they’re holding the CV boot tight and in place.
- Give them a Massage - The CV boots are rubber, and rubber should be pliable. If they are dry and inflexible, they don't have many miles left on them. Get in there and pull them, twist them, push the folds apart and look into the crevices. Look for any signs of cracking or cracked rubber, look for splits and cracks. Often times you won’t see these with just a casual glance - you need to get your hands on the boots.
- Listen closely - Put the transmission in neutral and spin the brake disc. Often times you will be able to hear a CV joint that is starting to go bad if you listen closely. Between engine and road noise the quiet clicking of a joint that has stated to fail is easy to miss when driving, but much more obvious from under the car with the wheel off.
- Clean, road test, repeat - Finally, if you can’t see any cracks or leaks, but you want to be sure, give everything a good clean and then snap a picture with your phone. Do a test drive, making sure to stay on clean roads and parking lots, and then have another look. On the test drive, be sure to do lots of tight turns to really flex the CV joints. If there are any grease spots when you look again, you know your CV boots are weeping. Simple.
What to do next?
If you do find a leaking of torn CV joint boot, the proper course of action is to remove the entire drive axle and replace the boot, and often the CV joint. Depending on how many miles the car has on it, a rebuilt drive axle complete with CV joints and boots is likely the solution.
In a pinch, if the CV joint appears to be in okay shape otherwise, a split CV joint boot can be quickly installed. Just like they sound, split boots, or quick boots, are sliced down one side to allow them to be fitted without removing the axle. Unfortunately, even the best split boot with good adhesive to seal up the split, isn't as good as an unsplit boot.
But if you have a torn leaking boot, a split boot will keep the CV joint from going bad for a few thousand miles until you can get around to replacing the entire axle. When the time comes to replace the drive axle, you will find information in your Haynes manual, but her is a general how to - Drive Axle Removal and Replacement