The power steering rack is what moves the tie rods back and forth when the steering wheel is turned. If your steering makes noise, feels like crap, overly-stiff, or, in my case, the wheel doesn't want to return to center when you come out of a turn, then your steering rack may be going bad or be damaged. Replacement can be done with a little time and patience, saving yourself about a thousand dollars over what a shop would charge you. But first, a little background:
A few weeks ago, I stupidly took a right turn too quickly during a light snow, forgetting my Wintersport M2s are now on their 6th season and not quit as invincible as they used to be. I slid pretty hard into the curb and threw the car horribly out of alignment.
So I took the car to an independent shop, where they realigned the car and replaced the tie rods and ball joints. (Ended up doing both sides, since they had 136,000 miles on them and were shot anyway). Even though the car was now perfectly aligned, the steering was still overly stiff and difficult to control. I took the car back to the shop for another look, and they declared that my little rendez-vous with said curb destroyed the steering rack. (I was a little peeved that they didn't discover this fact when I first had the car there, but maybe they were trying not to throw salt in my wound...)
The shop quoted me about $1300 to replace the steering rack. I imagine a dealer would want upwards of two grand or more. I did a lot of shopping around, and rebuilt steering racks for the TT go for between $500 and $800 (usually with a $200 core charge). I eventually found a used one (with 30K miles on it) for $385 from Shokan (with no core charge). Yes, it is a risk buying a salvaged unit, but I would think with 136K miles currently on my TT, this one should outlast the car, barring any more run-ins with curbs.
Replacement of the steering rack rates right up there with a timing belt job on the PITA-meter, especially if you do it laying on the garage floor (which we did). I can imagine this is considerably easier on a lift. Plan on a full day. It involves draining the power steering fluid, disconnecting tie rods, dropping the subframe, removing the rack, switching the tie rods and some other parts over to the new one, reinstalling, and finally an alignment from your shop. No special tools needed, except maybe a tie-rod removal tool, but I just used a BFH and some penetrant spray. You will need a variety of sockets (some big ones) and a torque wrench (if you care about that sort of thing).
Here are the parts needed (and my comments). I got all of the hardware, except the rack and the Powerflex bushing, from World Impex.
8N1 422 061 D - Power steering rack (This is for a quattro. I believe a FWD has a different part number due to different hose routing.)
N 100 722 02 - Bolt that holds the steering shaft joint to the steering rack pinion. The Bentley manual says to "always replace" this bolt, but I don't see why -- it's a plain old bolt that you can loosen and tighten. If I did this again, I would reuse this bolt.
N 907 528 01 - Rear subframe stretch bolts. You'll need two.
N 907 349 01 - Front subframe stretch bolts. Two again.
N 100 155 06 - Steering rack bolts. Four required. Holds the steering rack to the subframe.
N 013 848 6 - Washers for fluid return line. Two needed--one on each side of the bolt connection.
N 013 849 4 - Washers for fluid feed line. Two needed--one on each side of the bolt connection.
N 903 213 02 - Tie rod lock nuts. Two needed.
N 905 970 01 - Dogbone mount bolt.
N 102 466 02 - Transmission mount bolt.
G 002 000 - Power steering fluid. About 1 liter.
Steering rack bushing -- optional. I used the Powerflex polyurethane bushing from TTStuff. My old rubber one looked fine, but since I had the rack out I thought I'd give the Powerflex one a try.
Two small and two large hose clamps for the tie rod boots.
Alright, let's get down to bizness... (Please forgive the filty condition of my car. It is February in Chicago, every road surface is covered in layers of salt, and the temperature has been in the teens for the past two weeks.)
Center your steering wheel. Take off the plastic panel behind the pedals by unscrewing the two plastic screws.
You'll see the steering shaft.
The Bentley manual warns "Turn the steering wheel into center position (wheels straight ahead) and do not turn during repair, since the spiral spring can damage airbag unit."
HOWEVER - There is a bolt there that you have to loosen. And that's impossible, unless you turn the wheel to get to the head of the bolt. So turn it slightly until you can get a wrench on the head. My wheel actually locked when I started turning, which was good because now it can't
be turned during this procedure.
Here's the head of the bolt, at the bottom of this u-joint:
Pull up on the steering shaft. It telescopes into itself. Pull it off the splined shaft.
Crack your lugnuts and jack up the car and support it with jackstands -- as high as you can get it. You're going to be under there most of the day. Take off the the front wheels. Remove the plastic belly pan.
On the belt side of the engine, towards the front, under the car, find the power steering pump. Get your drain pan ready. Slide the clamp up from this hose:
Pull off the hose and let the fluid drain.
Disconnecting the tie rods. Loosen the lock nuts with an 18 mm socket.
If the bolt turns with the nut, hold the bolt still with a 6 mm allen wrench and turn the nut with a box end wrench.
Pop out the tie rod ends from the knuckle. Here's where you can use a tie rod/ball joint removal tool.
I had a generic one, but the forked end wouldn't slide onto the shaft of the ball end. So I sprayed it with some PB Blaster, let it soak, and whacked down on it with a hammer until the tie rod end dropped out. I left the nut on the end of the threaded part to keep from hitting the threads.
Disconnect the headlight leveler arm from the control arm on the driver side.
Looking through the driver side, you'll see the steering rack. Remove the bolt holding the lower power steering line. The socket is on it in this picture.
Use an extension.
Under the car, remove the two bolts on the transmission side of the dogbone mount.
Remove the four bolts holding the steering rack to the subframe. (13 mm I think?)
Put a floor jack with a chunk of wood underneath the subframe to support it. Remove the four subframe bolts with a 21 mm socket. These mf'ers are tight, so use a breaker bar if you have one.
The subframe should now be unbolted. Lower the jack a bit. The frame won't just drop out (mine didn't, at least) so you might need to pry at it to get it to come down.
Before you get the subframe down too far, disconnect this hose clip on the passenger side:
Go back around to the driver side and disconnect the upper power steering line.
Remove this exhaust hanger rubber thingy at the rear of the subframe.
It'll slide off if you pry at for a while.
Drop the subframe the rest of the way. There is a corner of the plastic wheel well liner on the driver side that might need to be disconnected (torx 25 screw). Mine ripped as the subframe was coming down.
You should be able to pull the steering rack out now. Rack gone:
Everything you see on the old rack (bottom) needs to be moved to the new rack (top).
I decided to try the Powerflex polyurethane steering rack bushing. Smeared it with the supplied grease before sliding it on.
Note the direction of the arrow points towards the front of the car when installed.
Pull back the plastic boot (which will be held on by single-use clamps if your tie rods have never been touched) to find this nut. Loosen it. It takes a pretty big wrench. (I used a vice grips.) Note the metal shavings on mine -- ya think anything was damaged in there??
Also look how crooked it sticks out! It's supposed to come straight out. No wonder I had a tough time controling the car.
Take the other side off too.
Put these on the new rack and tighten them down.
Center the tie rods. Use a caliper to measure the distance on the left side from the inside of the nut to the outside of the steering rack. It should be 33.5 mm. This will make sure the wheels and the steering wheel are straight when you reinstall.
You can adjust it by turning the steering pinion.
OK, ready to reinstall.
Load the rack back on the subframe where it came out. Thread in the bolts, but don't tighten yet.
Bolt this line on, with a new washer on each side of the bolt. Torque to 45 Nm/33 ft-lb.
Note -- This is where I screwed up. I somehow didn't attach this line exactly at the right angle, and it rubbed against the axle. Make sure this gets lined up properly and doesn't rest on the axle.
Jack up the subframe a bit and slide the rubber exhaust hanger bracket back on.
Now raise the subframe, making sure to line up the steering pinion with the hole on the underside. This can be kind of tricky, and actually took three of us to accomplish: two of us on the floor pushing the subframe forward, and the third person working the jack. Thread in the old subframe bolts. (The new ones should be used by your alignment shop, since they may need to move the subframe around.) Remember to check to make sure no power steering lines are resting on the axle.
Bolt the lower line on, with a new washer on each side of the bolt. Torque to 38 Nm/28 ft-lb.
Tighten up the steering rack bolts. Torque to 20 Nm/15 ft-lb, then add 1/4 turn.
Reattach and bolt down this hose bracket on the passenger side.
Tighten up the subframe bolts, 100 Nm/74 ft-lbs, plus 1/4 turn, each.
Bolt on the dogbone mount, new bolts, 50 Nm/37 ft-lb each.
Reattach the tie rod ends, new lock nuts, 45 Nm/33 ft-lb.
Reattach the headlight leveler arm.
Reattach the power steering hose to the pump and slide on the clamp.
Reattach the steering column and tighten the bolt. You'll have to turn the wheel a little to do this. Reinstall the plastic cover.
Fill the power steering reservoir with fluid and start up the engine. It should suck the fluid down pretty quickly, so try to keep filling. It might bubble up a bit as the air works its way through the system, so have some rags ready if it bubbles over. Turn the wheels all the way to one side and then back to the other several times and keep adding fluid until it doesn't take any more.
Reinstall the skid plate, bolt on your wheels, lower the car, torque the lugs, go get an alignment, and enjoy your renewed steering.