Upper Ball Joint Replacement
on the 1984 300D (W123)
by littlerobot
9/17/10
How To: Upper Ball Joint Replacement, step by step with pictures. W123
My upper ball joints are terrible. They need replacing. Here's how I did the passenger side. It took about an hour.
Remove the air filter housing under the hood.
This gives us access to the bolt holding the ball joint arm to the frame of the car. Don't loosen it yet, just remember where it is.
Now we jack up the car using a hydraulic jack. I placed the jack directly under the jack-up ports behind the wheel. There is a piece of wood between the jack and car. I've placed wheel chocks behind both rear wheels. Now, remove the tire.
Here's where the top of the steering knuckle connects to the upper ball joint. Mine is crusty, with bad rubber on the bushings and on the ball joint itself. Grab your breaker bar or socket and loosen the bolt connecting the ball joint to the steering knuckle arm.
Now we have the car jacked up, but the weight of the suspension system is pulling downward. This will help us in a moment. After you've removed the bolt you want to use a cool tool.
This is a "joint popper". It's an invaluable tool for suspension work. I purchased this one from Harbor Freight for 15 bucks or so.
Place our cool tool on the joint like so. This is where the weight of the steering knuckle pulling downward helps us. Turn the tool until the joint pops apart. It came apart very easily for me.
Pop. The joint separates and is no longer connected to the upper knuckle arm.
Now remove this bolt. There is a rubber bushing under it. Pull that off too.
Now we move to the top of the car.
The bolt runs horizontally through this part of the car. The nut is facing us. The bolt itself is facing the battery. It's a little tough, but you should be able to get a crescent wrench or open ended wrench on it, then place a breaker bar on the nut itself.
Break the nut loose and remove it from the bolt. Here's where it gets a little tough, because the high-side of the air conditioning runs between the battery and where we need to pull the bolt out. I tapped the bolt from the other side with a screwdriver, pushing it out toward the battery, and tried to hold the high-side R134 line out of the way. I managed to get it out, but here's where we change a little something.
Because the bolt and nut faces this way, it's difficult to get out. But....
When we put it back in we are going to put it this way, technically its backwards, but its going to be WAY easier to put back in this way, and WAY easier to take back out if we ever have to work on this ball joint again. It's a win-win situation. Don't worry, it won't affect performance or safety.
Pull the old ball joint out.
Also remove this rubber grommet and replace it with a new one.
Get your new ball joint and push it into place.
Move to the top of the car. Put the bolt back through the frame like this and tighten it up.
Tighten this bolt with our new rubber grommets.
Notice that the distance between the bolt and the knuckle arm is like an inch or so. What wee need to do is "lift" the knuckle arm. Here's an easy way to do it.
Slide a safety jack under the axle. Make it as close to the brake rotor as you safely can. Extend the top of the safety jack until it is touch the suspension arm.
This is what we are looking at. The red hydraulic jack on the left will (slowly and carefully!) lower the body of the car, while the safety jack holds the knuckle in place. As the car lowers, so does the bolt on the upper ball joint, with the safety jack holding the knuckle in place, the two will meet.
Line the hole up with the bolt. When they are aligned, slowly, slowly, slowly lower the hydraulic jack, causing the ball joint bolt to go through the hole.
Success. Place the nut on the bolt and tighten it. Double check that all your nuts and bolts are tightened. The new parts I purchased came with the nylon-lined bolts that stay tight. No need to use loctite or anything. When you are done, jack the car back up using the hydraulic jack, remove the safety jack, and put the tire back on. Lower the vehicle. Then put the air filter housing back on, go in the house, and grab a beer.
You rule.
Disclaimer: I am not a licensed mechanic. I am a DIY guy. Follow all safety guidelines and wear eye protection. Use the proper equipment and tools, and be careful. Failure to follow safety precautions can lead to injury, or even death. Always use safety jacks when raising the car up on hydraulic jacks. The brake pads of your car may contain dust particles that are hazardous to your health. When in doubt, wear breathing protection, such as a respirator. The use of nitrile gloves is highly recommended, as some fluids, such as motor oil, can be damaging to the skin.
Discuss this DIY here.
-littlerobot
CategoryDiy
