My front-wheel drive car makes a clicking sound when turning. Is anything wrong?

Yes. A clicking sound when turning is one of the classic symptoms of a worn or damaged "constant velocity" (CV) joint. Your car has four such joints on the two front axles: two inboard joints and two outboard joints. The outboard joints are the ones that make a clicking sound when they go bad.

Inside the joint are six steel balls, positioned in grooves between an inner race and an outer housing. The balls are held in position by a cage that looks something like a wide bracelet with windows or slots cut in it. When the joint is new, the balls fit tightly into the cage windows. But as the joint accumulates miles, the cage windows become worn and allow the balls to rattle around. The grooves in the inner race and outer housing also wear, which further contributes to noise.

When driving straight, a worn CV joint is usually quiet (constant noise would indicate a bad wheel bearing or other problem). But when the wheels are turned to either side, the joint bends causing the balls to click as they slide around in their cage windows and grooves. The noise is usually loudest when backing up with the wheels turned. Repacking the joint with grease won't help because the joint is worn and needs to be replaced.

The "normal" life of a CV joint is usually 100,000 miles or more. But a joint can fail prematurely if the rubber boot that surrounds it is damaged or develops a leak.

Cv Joint Boots

The boot, which is made of rubber or hard plastic, serves two purposes: it keeps the joint's vital supply of special grease inside, and it keeps dirt and water out. After five or six years of service, it's not unusual for the boot to develop age cracks or splits. Boots can also be damaged by road hazards or a careless tow truck operator who uses J-hooks to tow your vehicle.

Once the boot seal is broken, the inside grease quickly leaks out. Starved for lubrication, the CV joint soon fails. Dirt and water can also enter the boot and contaminate any grease that's left inside. Either way, a damaged boot is bad news for the joint.

CV joint boots should be inspected periodically (when the oil is changed is a good time) to make sure they are not cracked or torn, and that the clamps are tight. If you see grease on the outside of the boot, it is leaking and needs to be replaced (the sooner the better). If a clamp is loose and the boot is leaking grease at one end, the clamp needs to be replaced.

Original equipment boots are a one-piece design, which means the driveshaft and CV joint have to be removed from the vehicle and disassembled to replace a bad boot. However, there are aftermarket "split-boots" designed for easy do-it-yourself installation. The split-boots eliminate the need to remove and disassemble the joint and driveshaft. You simply cut off the old boot, clean out as much of the old grease as possible from the joint, pack the joint with fresh high temperature CV joint grease (never ordinary chassis grease), then install the new boot. Most split-boots have a seam that is glued together. The seam must not have any grease smeared on it and the glue must be applied carefully for a good seal. Also, the vehicle must not be driven until the glue has cured (about an hour or so).

NOTE: Most professional mechanics do not use split-boots because (1) they don't think a split-boot is as reliable or as long-lived as a one-piece original equipment style boot, and (2) they don't like the idea of installing a new boot on a questionable joint.

By the time a damaged or leaky boot is noticed, the joint has usually lost most of its grease and/or been contaminated by dirt. Unless the joint is removed, disassembled, cleaned and inspected, there's no way to know if it is still in good enough condition to remain in service. If it's making noise, replacing the boot would be a waste of time because the joint is bad and needs to be replaced (most new joints come with a new boot, clamps and grease). But even if the joint isn't making any noise, it may still have wear or internal damage that will soon cause it to fail.

WARNING: A CV joint failure can cause loss of steering control under certain circumstances. If the joint locks up, it can prevent the wheels from being turned.