Audi A4/S4 Front Upper Control Arms Replacement – The Damn Pinch Bolt!!

If you have an Audi A4, A5, Q5 or some VW Passats and other VAG group cars, you might just have this style of 4 link front suspension. While the handling characteristics of this setup are pretty good, the wear and repairability, well, not so much. I need to replace the two upper arms on both sides of my S4’s suspension. It has started to have small tracking issues, and inconsistent tracking too. On one road it will pull very gently left, and another it might pull slightly right. It also tram-lines quite hard now, where bumps and grooves in the road pull the car in their direction rather than the car staying on it’s own course. And a visual inspection reveals a fair bit of cracking and play in those bushings.

To replace these arms, it seems pretty simple. There are only three bolts you’ll need to remove per side, but one of them, I can almost guarantee you, will not come out on its own. That would be the pinch bolt – the bolt that squeezes the aluminium knuckle together and locks both of the ball joints in place. Because it’s a steel bolt in an aluminium block, the corrosion from dissimilar metals is pretty severe, and basically it seizes itself in place good and proper.

Happily we developed a bit of a technique that worked pretty flawlessly on both rather crusty sides. So, let me run you through the tools you’ll need. First a jack and jackstands to lift the car, a socket set which includes a 17mm for the wheel bolts, 16mm spanners and sockets for all three bolts and nuts, a variety of extensions, a torque wrench that can do 40Nm for the pinch bolt, 50Nm for the bushing bolts and 120Nm for the wheel bolts. You might also want a breaker bar to loosen things up. You will need a drill and some quality high speed steel drill bits, a propane torch (I have a cheap propane/butane torch from B&Q that worked perfectly fine), some way to cut the bolt, I used an angle grinder but a dremel or even a hand saw could have worked if needed. You’ll also need some punches, a hammer and mallet and pry bars. If you have an air hammer you might find this easier, we didn’t have one and we made it work so you don’t need one, but it might help. You will also need either a ball joint fork that is wide enough to fit on the ball joints, or what I’d actually recommend is a ball joint press kit. The one I got was something like £40 or £50 for 5 different press/pullers and they worked flawlessly here.

As for supplies, WD40, anti-seize, and replacement arms and bolts – I got this Meyle kit on ebay for £140 for all four, which is an absolute steal as Euro Car Parts wanted something like £200 just for the cheapest OEM stuff, when these are top shelf kit! Finally I’d recommend having some M8 nuts handy to help spin the bolt free.

As for the process, first jack up your car and remove your wheel. It’s good practice to leave the wheel under the side sill just in case the jack fails and you happen to be under it. You can also position a jackstand under it for better protection. After the wheel is off, use a 16mm spanner and ratchet to break free the two bolts and nuts holding the arms to their mounts on the car. They’ll be tight as hell, but it’s good to remove the nut now but leave the bolt in place.

Once those are off, remove the nylock nut on the end of the pinch bolt. This is where the heat comes in. We used some aluminium foil to protect the ball joint boots, then spent a good 10 – 20 minutes heating the knuckle. You want to heat right where the bolt travels through the part, especially closer to the side with the exposed threads. As you heat it the aluminium will expand faster and further than the steel bolt which will help free it up.

Once it’s hot, wind two nuts on the threads and lock them together so you can stick a socket on the end, and a socket on the bolt head, and gently twist them together rocking back and forward. If the area is hot enough you should be able to start turning the bolt – and a whole lot of corrosion will start falling out. If it doesn’t turn, don’t force it too hard as you don’t want to snap the head off. Try heating it again, and try cycling that heat as well to help break up those bonds. You should be able to get it turning, if you do, start trying to unscrew it. You likely won’t be able to just unscrew it all the way though, so unscrew it just enough to have the head no longer making contact with the knuckle – enough you could push on the back of it with a pry bar.

Once it’s just proud, use a grinder or other cutting tool to lop the remaining exposed threads off so it’s almost flush with the knuckle. Use a punch to centre a hole for your drill bits to sit in, then drill a fairly small hole down the centre of the bolt. It’ll need to be somewhere between two and four centimetres deep, but don’t worry if it’s off centre as that will end up being useful later. Also, you can use WD40 as a lubricant and coolant to keep your drill bits cool. If they overheat they will get dull real fast and become pretty useless.

You’ll need to step up a drill bit to widen the hole, and again, up until around 7mm, where you are likely to be off centre and will have drilled away a full side of the bolt and threads. That’s where you can stop and heat the knuckle again. Once it’s hot, use a pry bar to pry on the backside of the bolt head while unscrewing it. It should start winding out, and with enough pressure on the back of the bolt head it should make its way out.

If you’ve managed to get that out, congratulations! That is a triumph in and of itself. The next step is to use one of the ball joint presses to push the old arms out. They will also be full of corrosion and may take some effort to get them out, but they will come eventually. Once free you can remove the bolts from the inboard side and slide the arms out. Make sure to give the pinch bolt and ball joint holes a good cleaning – a brush or even a gentle filing will work, and a spray with some brake clean will help too (just make sure the knuckle still isn’t too hot!).

Then I would highly recommend coating the ball joint shafts in all of the anti-seize before sliding the arms into place, sliding their new bolts in, then pushing the shafts into their respective holes. If you can’t get them in by the way, Audi left a helpful access hole in the engine bay, just pull the silicone cover off and use the handle of a mallet to tap them into place. Then lather a new pinch bolt up in anti-seize too and slide it in.

Before you tighten any bolts, the suspension needs to be at ride height. If you have a spare jack, or the car is on jackstands, you can use a jack under the knuckle to raise it all up in place before tightening both bolts to 50NM + 90°, and the pinch bolt to 40Nm. Then you can let it back down and put the wheel on, torquing those to 120Nm. Of course you’ll need to repeat that for the other side – it’s always recommended to match both sides here – but then that’s it sorted!

I hope the description of the pinch bolt removal is helpful, it was the main thing I was afraid of when planning and attempting this repair, but after we got the technique down I think one side took something like 3 hours all in, so in theory could be done in a day.