The rear upper suspension arm, sometimes called the radius arm or “Link assembly - rear suspension upper” as listed in the parts catalogue, acts as a pivot and is one of the main parts of your rear suspension. At one end it is bolted into the rear subframe, at the other end it is bolted to the rear hub via the upper ball joint and between the two is where the bottom of the shock absorber is bolted to.
This part probably takes the most force when bouncing along potholes etc.
It is no surprise then that when the oil filled rubber bush at the subframe end starts to fail you will get a quite distinctive knock as you go over potholes and speed humps etc. You should get a distinct, sharp knock as the suspension is shock loaded and you will probably be able to hear which corner it is coming from.
To confirm where the knock was coming from you can jack the car up and rock the wheel. I often do this but the wheel obscures most of the things you are trying to see. Because of this I knocked up a tool to allow me to rock the hub without the wheel in place.
It is just a piece of bar with a piece cut out of the centre to clear the hub nut and 2 holes drilled in for the wheel bolts. Make sure the length of the bar is short enough to clear the wheel arch.
By rocking the hub and putting your hand on bushes and joints you should feel any excessive play.
Using this method I found the Upper arm bush to be the problem.
As this part is not able to be re bushed, you need to buy a complete arm with bush.
LH (nearside) arm is part no RGD000930 while the RH (Offside) arm is part no RGD000920
This is a fairly straightforward job if you have the right tools.
First of all jack the car up, secure on axle stands and remove the wheel.
Now give the nuts and bolts a clean and a good dose of release oil, such as PlusGas (Not WD40), as this will help you remove the parts easier.
Try not to get any oil on the brake disc, if you do then wipe off the oil with solvent such as brake cleaner.
Use your jack under the hub (NOT THE DISC) and compress the suspension just enough to not lift the car off the axle stand.
This will release some of the load off the bushes and bolts, making it easier to remove the parts. You can adjust the amount of compression to suit by raising or lowering the jack, but try not to lift the car off the axle stand.
Now remove the nut holding the bolt through the subframe bush, but leave the bolt in place for now. Both the nut and the bolt are 19mm.
Remove the bolt holding the bottom of the shock absorber to the arm using a 15mm socket. Try to use the jack to get the best position so that is not too much weight on the bolt.
Now remove the nut from the upper ball joint using a 19mm spanner.
I thought I would get away with just using the spanner, but the ball joint started turning, so I had to use a torx key to hold it steady.
The fact it turned was actually a good thing at it broke the tolerance fit on the tapered ball joint. If this doesn’t happen you will need a ball joint splitter.
Now you can withdraw the bolt from the subframe.
Spot the design error.
If the bolt goes in this way round, you have to drop the anti roll bar slightly as it is in the way.
You only need to remove the 2 x 13mm nuts holding the anti roll bar, which gives you enough room.
Now, using a screwdriver, or similar lever, move the spacer out of the way.
Which will give you enough space to manoeuvre the upper arm around the spring/shock absorber.
If you have ABS then you may need to unclip the lead from the sensor from the small fork like bracket that you can see on the last pic just below my hand. It simply pulls out of the bracket.
You may also need to remove that bracket and fit to the new arm if you have bought new.
I am replacing with one that I had on a spare subframe.
Manoeuvre the replacement arm into place. I placed the spacer in place and pushed the bolt just enough into it to hold it while I jiggled the new arm in. When you get it roughly lined up you can push the bolt further through until it emerges at the other side of the subframe bracket and put the nut on but don’t tighten it.
Place the threaded part of the top ball joint through the arm and lightly tighten the nut to hold it in place. Now use the jack to line up the arm and the bottom hole of the suspension and screw the bolt through the arm, but don’t fully tighten yet.
You then need to compress the suspension again to just before it lifts off the axle stand. This is called preload.
This is essential when tightening any suspension bushes as this is the position it will normally sit when the wheel is on the ground. If you were to tighten the bushes without compressing the suspension, when you were finished and the car was lowered onto the ground the bushes would constantly be under torsion, even at rest, and this would cause premature failure of the suspension components. It can also cause the suspension not to sit properly.
Now you need good old Mr torque wrench, or probably a couple as the torque settings are from 22Nm to 100Nm.
The sequence you tighten in is up to you, but I started with the upper ball joint which is 19mm and a torque setting of 54Nm. A new Nyloc nut should be used.
You may need to use the key and spanner until the tapered shaft starts to “bite” otherwise it will just keep turning. If you need to do this, just do it until you start feeling a bit of resistance and then finish off with the torque wrench.
Next, using a 15mm socket and a torque wrench set to 100Nm, tighten the lower shocker bolt.
And lastly, using a 19mm spanner on the bolt side to stop it turning, use a 19mm socket and a torque wrench set to 100Nm to tighten the main bolt through the subframe.
While the suspension is compressed, don’t forget to retighten the anti roll bar clamp 13mm nuts to 22Nm.
If you did unclip the ABS sensor lead from the arm earlier then remember to clip it back into position.
You can now lower the suspension (assuming the axle stand is still in place), refit the road wheel, remove the axle stand and lower the car onto the wheel.
The job is now done and just needs you to take a test drive to check everything feels OK and your knock should be gone.