Ball joints allow your vehicle's suspension to move up and down while, at the same time, allowing the wheels to turn left and right. Over time, the ball joints may wear out. In the event that a ball joint begins to loosen, you will hear thudding sounds from the front as the joint vibrates in the housing. If it increases, the steering may stiffen, so you may find a point where it seizes when you turn the steering wheel. There may also be a drift or screeching sound in addition to the binding point. Luckily, it's possible to quickly and easily check your ball joint for wear before you start experiencing serious steering or suspension problems.
Basically, a ball joint is like a ball and socket joint in your body, made up of a housing, the ball, a wrap layer, and in some cases a Belleville washer or spring. A Belleville washer is a conical shaped washer that keeps the joint centered and under tension. Like a ball and socket joint, the joint wears out from accumulated stress over a long period of time and needs to be serviced, especially in case you notice a pounding noise when turning. Always refer to the user manual for more specific advice and instructions. Vehicle manufacturers build different suspension configurations, so read the manual to determine what type of ball joints your vehicle uses.
Part 1 of 2: Checking Vehicles with Independent Suspension System
Step 1. Find the wear indicator
While the vehicle is still on the ground, look under the vehicle, at the bottom of the steering linkage that is attached to the wheel. The most common indicator is a grease fitting that acts as a wear indicator. This fitting, or boss, should protrude approximately 1.3 centimeters (one-half inch) into the bottom of the ball joint housing. As the boss wears it will sink into the housing. As long as the boss protrudes, the gasket is in good condition. Once the boss is level with the housing, or even deeper, you will need to replace the ball joint.
This applies to older vehicles. Most new vehicles do not have wear indicators or a grease fitting. If you can't find a wear indicator, or the indicator doesn't give you a clear enough signal, lift the vehicle to inspect the joint more closely
Step 2. Raise the front of the vehicle
To check the lower ball joint under load, the manufacturer will recommend that you place a jack under the lower control arm of the front wheel, as close to the ball joint as possible, and then lift the vehicle until the wheel is off the ground. If you don't do this, there will still be tension on the ball joint when you lift the vehicle, making it difficult to move and check the joint slack.
Make sure there is no compression (in English) in the suspension when you check the ball joint. In case you have control arms of different lengths, make sure the top stop does not touch the control arm
Step 3. Shake the wheels and check their play
Make sure the vehicle is on the jack safely. The vehicle must be on frame supports when lifting it while working on it. Place the dial gauge next to the nut or next to the spindle and move the wheel in and out to check for radial wear.
- For vertical clearance, position the dial gauge against the tie rod nut or ball joint housing, depending on the manufacturer. Grab the wheel at the top and bottom (12 and 6 o'clock) to lift it up and pull it down. Place the dial gauge next to the nut and pull the wheel down by moving it in and out to check the radial clearance of the joint.
- Read the dial comparator and compare it to the manufacturer's specifications. In case the movement exceeds the specification, replace the ball joint.
- Skilled mechanics will also be able to check the play simply by touch or by listening carefully for any noise or easy movement that suggests the ball joint is worn. Alternatively, it is also possible to have a helper watch the joint itself closely to make sure it appears loose as you move it.
Part 2 of 2: Checking Vehicles with McPherson Suspension Bars
Step 1. Find the grease fitting
If your front suspension uses McPherson bars, look for a wear indicator, which will usually be a grease fitting. Hold the grease fitting and try to move it. In case the accessory moves inside the housing, you will need to replace the ball joint.
Step 2. Raise the vehicle onto the front cross member
It is not a good idea to lift many front wheel drive vehicles with bar suspension using the lower control arm, therefore it is best to consult the owner's manual before attempting to check the ball joint. Generally, you will lift the vehicle at the point indicated on the frame cross member as you normally would.
Allow the McPherson bars to unfold as much as possible before attempting to check the wheel play
Step 3. Use your hand to check the top-to-bottom play of the ball joint
Shake the bottom of the wheel to check for any play in the ball joint. If there is any slack in the ball joint, you will need to change it.
Step 4. Listen
The ball joint on a vehicle with suspension bars must be quiet. Any sound similar to a click when you move it will indicate that it has worn out and is not working as it should. In case you notice a significant slack you will need to change the kneecap.