Front Upper Control Arm Bolt Questions

[myfreeaudi]

This is covered elsewhere and is a perennial problem as it seizes into the alloy steering knuckle. One popular solution is to heat it until red hot and the bolt will come out.

1. Is heating the alloy steering knuckle at the bolt a good idea? One commenter says heat will melt the aluminum, although I believe it is aluminum alloy. My magnet does not stick to the steering knuckle although it does to the bolt. And what about taking the temper out of the knuckle with heat?

2. I did one side years ago when my son owned the car and it was a few years old. It came out with some hassle, no heat. I slathered it up with anti-seize so we will see how easily it comes out. Any recommendation on what lube to use to suppress corrosion and sticking of the bolt?

3. The 2001 B5 bolt is in from back to front so the nut faces out. What about putting the new bolt in front to back so the head faces out and can be spun by an impact wrench next time? In fact, my 2003 bolts are in front to back. And yes, I hope there will not be a "next time."

4. What about using a slightly smaller diameter bolt to reduce contact and discourage the setting up? After all, the holding is in the 2 pinch fittings on the knuckle so as long as they are tight, it should be good. 10mm = 25/64 so 24/64 = 3/8 with the same pitch should be right.

5. One video says to pry the pinch fitting apart with a pry bar. My manual says do not pry these apart. Any opinions on this?



Thanks,

John

[MetalMan]

1. You posted in the B5 section. The B5 A4 only came with steel uprights. The early B5 S4 and all B6 A4 came with aluminum uprights.

2. Any anti-seize compound should be fine.

3. Doesn't matter. Do whatever is most convenient for you. Just make sure you'll be able to get a torque wrench on there.

4. A smaller bolt will mean a lower torque setting, which means less tension on the pinches, and less compressive force on the upper control arm ball joint ends. 3/8" isn't a huge difference and might be fine, just make sure to get a high grade bolt. Otherwise, it kinda saddens me at the prospect of a non-metric bolt going onto one of these cars.

5. Personally I wouldn't pry with more than a medium-ish sized screwdriver. It's probably not advised to pry the pinches of an aluminum upright, but should be alright on steel.
I usually use a little prying to aid in removal and installation of upper control arms.

[myfreeaudi]

1. You posted in the B5 section. The B5 A4 only came with steel uprights. The early B5 S4 and all B6 A4 came with aluminum uprights.

2. Any anti-seize compound should be fine.

3. Doesn't matter. Do whatever is most convenient for you. Just make sure you'll be able to get a torque wrench on there.

4. A smaller bolt will mean a lower torque setting, which means less tension on the pinches, and less compressive force on the upper control arm ball joint ends. 3/8" isn't a huge difference and might be fine, just make sure to get a high grade bolt. Otherwise, it kinda saddens me at the prospect of a non-metric bolt going onto one of these cars.

5. Personally I wouldn't pry with more than a medium-ish sized screwdriver. It's probably not advised to pry the pinches of an aluminum upright, but should be alright on steel.
I usually use a little prying to aid in removal and installation of upper control arms.

Great, thank you for the advice, and so quick!

[seanf86]

3. The 2001 B5 bolt is in from back to front so the nut faces out. What about putting the new bolt in front to back so the head faces out and can be spun by an impact wrench next time? In fact, my 2003 bolts are in front to back. And yes, I hope there will not be a "next time."

I like the nut facing out so you can remove it and get an air hammer on there, if the bolt is really seized putting an impact on it might just shear the head off. Generally the steel knuckle cars the pinch bolt is easier to remove than the alum knuckle cars, having done this about a dozen times now I much prefer the steel uprights.