Brake System

The brakes on these cars are adequate for normal driving. If you drive hard most of the time or frequent track days, you should think of upgrading. More on that later.

Brake problems are not unheard of, especially as these cars are hydraulically assisted and not vacuum assisted as on other cars. This means that the "power steering" pump not only supplies hydraulic pressure for the steering but also brakes too.  Maintenance should be carried out on this system too to ensure trouble free operation and long component life.

Hydraulic Fluid Replacement

First thing to note is that YOU MUST ONLY USE AUDI HYDRAULIC MINERAL OIL, PART NUMBER G002000 and nothing else, especially NOT normal brake fluid. Remember that this is hydraulic assistance and not the actual brake system.

I am not sure that Audi specify a need to change this fluid but most enthusiasts recommend a change every 50,000 miles to help promote long service for the expensive components (pump, steering rack, etc). The job is easy for the DIY mechanic to do.

To start, jack up the front of the car and place on axle stands so that the front wheels are off the floor. Then remove the cap carefully from the reservoir. This is situated on the far left of the engine bay, just behind the washer bottle. I stuffed a rag around the reservoir to avoid spillages dropping down and making a mess. Use a suction device (I used a roast baster bought from a hardware shop for about 2 but a large syringe will do) to remove all the fluid from the reservoir. Next, turn the steering lock-to-lock a few times to remove the remaining fluid out of the rack. Also, pump the brake pedal until it becomes stiff as this will release pressure from the "bomb" and return more fluid to the reservoir. Once you have removed all the old fluid, clean out the reservoir and clean or replace the filter inside.

To refill, top up the reservoir with fresh fluid and start the engine. The system is self filling and bleeding so all you have to do is keep topping the system up as the new fluid circulates and fills the system again. Once the level is steady, slowly turn the steering from lock to lock to remove any trapped air in the system (often you can hear this as a "groan"). The capacity of the system is approximately a litre but I found I needed a little more than this so make sure you have two tins handy.

Once done, replace the cap, clean any spillages and take the car off the stands. Remember to dispose of the oil at an appropriate waste disposal point and not in the rubbish bin or drain!

Bleeding the Brakes

Always use a high quality brake fluid. I use Lucas DOT 5.1. This is a high performance, high boiling point fluid and is not as expensive as you may think. It is probably over the top for normal road use but I would rather be safe than sorry. I have used the car on a couple of track days and never had brake fade! Remember, DO NOT USE G002000 HYDRAULIC MINERAL OIL IN HERE!

The car has a specific sequence in which bleeding must be carried out. This is:-

  1. Brake master cylinder (If you don't bleed this first, you will never be able to bleed all the wheel cylinders)
  2. Proportioning valve ( press regulator lever firmly towards rear axle when bleeding rear brakes. The proportioning valve sits on the rear trailing arm on the left side of the car. Jack the car up, locate the valve and insert a 6mm drill bit between the lower spring hook and the roller so it will bias the brake pressure evenly front to rear)
  3. Right rear calliper
  4. Left rear calliper
  5. Right front calliper
  6. Left front calliper
  7. Clutch slave cylinder (below steering rack on top of gearbox)

Armed with this information, you can now use a "power bleed" system (Eazi Bleed and the like) or the good old fashioned way with a bleed tube, and a partner to pump the pedal for you.

Pad & Disc Changing

Before starting, check that you have the correct pads and also have new guide pin bolts. These have a coloured tip to lock the bolts (like a nyloc type arrangement). These bolts are normally supplied with new pads.

Jack up car and place on axle stands then remove the wheels.

Using open ended spanner to hold guide head pin, remove the bottom bolt which holds the calliper to the mounting bracket and loosen the top one. Rotate the calliper up out of the way and secure to the spring with a suitable length of string. Remove the pads.

Clean and lubricate the pistons (two of them on the front) with a little brake fluid and then gently lever them back into the calliper (Be careful the reservoir does not overfill as you will be forcing fluid back up too). For the rear brakes, the piston has to be screwed back in with a special tool (you can get this from Audi if you remortgage your house or else you can easily make something that will fit on the end of a ratchet).

If you're replacing the discs, remove the calliper mounting bracket so that the rotors will come off. These bolts can be tight and there is not a lot of room so be careful. The discs will come off easily and replacements fitted.

Replace the calliper mounting bracket back onto hub, using a quality threadlock or new bolts. Place your new pads into calliper mounting and apply some copperslip to the back of the pad to help reduce squealing. Replace the calliper into calliper mounting bracket very carefully, so as not to damage the rubber seals and also fit the anti-squeal shims (if you have them). Renew the guide pin bolts Tighten the calliper mounting bracket bolts, and guide pin bolts.

Replace wheel, wheel bolts, and torque to taste. Remove stands, lower car, and check brakes. Test drive and bed in pads per their manufacturer's instructions.

For the S2, I will only list here jobs I have done myself. For more details on S2 DIY, you need to visit the site of fellow Audi Owners Club Member, www.s2-audi.co.uk

 

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