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