2010-2011 Audi S4 Brake Fluid Type and Flush Interval

By Core Brake Parts Tech Team — Circleville, OH warehouse

The 2010-2011 Audi S4 uses brake fluid that meets FMVSS 116 DOT 4 (or SAE J1703), and Audi's maintenance schedule says to replace it every 2 years regardless of mileage. Audi's own fluid capacity chart for the S4 lists the brake system at roughly 1.0 liter (1.1 quarts) and specifies new fluid only. Below is what that means in practice, how to tell when your fluid is overdue, and what to do while the car is apart.

What Audi Specifies for the B8 S4

The 2010 and 2011 S4 are the first model years of the B8-generation S4, powered by the 3.0-liter supercharged V6 (engine code CCBA, 333 hp). Audi of America's fluid capacity chart for the 2011 A4, A4 Avant and S4, filed with NHTSA, lists the same brake fluid requirement for every car on the sheet, including the S4 quattro:

That capacity is an approximate system figure. A proper flush uses more than that, because you push fresh fluid through all four bleeders until it runs clean, so buy at least two liter bottles of sealed DOT 4 before you start.

Why DOT 4 and Why Every 2 Years

DOT 3, DOT 4 and non-silicone DOT 5.1 fluids are glycol-ether based and hygroscopic: they pull moisture out of the air through hoses, seals and the reservoir vent. Water lowers the boiling point. The federal standard, FMVSS 116, sets minimum boiling points for new fluid (dry) and for fluid that has absorbed a controlled amount of water (wet):

The S4 is a heavy, fast car, and hard stops dump a lot of heat into the calipers. When fluid in the caliper boils, it forms vapor bubbles that compress, and the pedal goes soft or sinks. DOT 4 starts higher than DOT 3 and keeps more margin as it absorbs water, which is why it suits this car. The 2-year, any-mileage interval exists because moisture pickup depends on time and climate, not how far the car is driven. A low-mileage S4 that sits in a humid garage still needs the flush.

Do not put silicone DOT 5 (the purple fluid) in the S4. It does not mix with the glycol fluid the system was designed for. Any fluid labeled DOT 4 that meets FMVSS 116 satisfies Audi's spec, and many owners who track the car choose a DOT 4 with a higher dry boiling point than the federal minimum.

Signs Your S4 Brake Fluid Is Overdue

• More than 2 years since the last flush. This is the only reliable test most owners have. Check your service records; if there is no entry, assume it is due.
• Pedal that softens after repeated hard stops and firms up again once the brakes cool. That is classic fluid fade from boiling in the calipers.
• Dark fluid in the reservoir. New DOT 4 is colorless to amber under the federal standard. Fluid that has gone brown or cloudy has picked up moisture and contaminants. Color alone does not prove the boiling point, but dark fluid is never fresh.
• Brake warning light or low level. A falling level usually means worn pads (the caliper pistons sit farther out) or a leak. Top up with new DOT 4 only and inspect before you drive hard.

A spongy pedal that is soft all the time, even cold, points to air in the lines, a leak, or a failing master cylinder rather than old fluid alone. Diagnose that before assuming a flush will fix it.

How the Flush Is Done on This Car

The S4 has four-wheel discs with ABS and stability control, so the job is a straightforward four-corner bleed with a couple of cautions:

1. Remove old fluid from the reservoir with a clean syringe and refill with new DOT 4 from a sealed bottle. Never reuse fluid you bled out.
2. Pressure-bleed or two-person bleed each caliper, working from the corner farthest from the master cylinder toward the nearest, until clear fresh fluid with no bubbles comes out. If a caliper has more than one bleeder, open each one.
3. Do not let the reservoir run dry. If air reaches the ABS unit, clearing it can require a scan tool that cycles the ABS pump. That is the main reason an independent Audi shop may charge more than a quick-lube.
4. If your car has the six-speed manual, ask whether the clutch hydraulic circuit shares the brake fluid supply and have the clutch bled at the same time if it does, so the whole system gets fresh fluid.
5. Tighten bleeders to the value in the factory service manual, top the reservoir to the MAX line, and confirm a firm pedal before moving the car.

For a home mechanic with a pressure bleeder, this is a one- to two-hour job. The risk is almost entirely in letting air into the system, so go slow and keep the reservoir full.

What to Replace at the Same Time

Because you will have the wheels off, a flush is the best time to check the rest of the brake system Audi lists for inspection: pad thickness, disc thickness, and the system for damage and leaks.

• Pads and rotors. If the pads are near their wear limit or the rotors are below minimum thickness, do them together and flush the fluid last. A matched kit such as the Brembo front brake kit with drilled rotors and ceramic pads for the 2010-2011 S4 takes care of both in one order. You can also browse brake pads and brake rotors separately.
• Brake hoses. Original rubber hoses on a car this age can swell under pressure and add pedal travel. Replacement brake hoses are worth considering if yours show cracking.
• Hardware. Fresh clips and pins from a brake hardware kit help new pads seat and release evenly.

If you replace any hydraulic part, such as a hose or caliper, the system must be bled afterward anyway, so combining that work with the scheduled flush saves labor.

Frequently Asked Questions

Can I use DOT 3 in my 2010 or 2011 Audi S4?

Audi specifies DOT 4 for this car. DOT 3 has a lower minimum boiling point under FMVSS 116, which reduces the fade margin on a heavy, powerful car. Use DOT 4.

Can I use DOT 5.1 instead of DOT 4?

Non-silicone DOT 5.1 is glycol based, so it is chemically compatible with the system. Audi's chart calls for DOT 4, which is widely available, and that is the safe choice. Never use silicone DOT 5.

My S4 only has 8,000 miles since the last flush. Do I still need to do it?

Yes, if it has been 2 years. Audi's schedule says every 2 years regardless of mileage, because the fluid absorbs moisture over time whether the car is driven or not.

How much brake fluid does a 2010-2011 S4 need?

Audi lists the brake system at about 1.0 liter (1.1 quarts). Plan on two liters of sealed DOT 4 for a complete flush so you can push old fluid all the way out of every caliper.

Should I shorten the interval if I track the car?

Yes. Track use heats the fluid far beyond street driving, and many owners bleed the calipers before each track event. The 2-year interval is Audi's figure for normal operation.

Sources

1. Audi of America, A4, A4 Avant and S4 2011 Fluid Capacity Chart (via NHTSA) - DOT 4 or SAE J1703 spec, new fluid only, approx. 1.0 L capacity, part number B 000 750, S4 3.0L CCBA
2. Audi of America, 2011 A4/S4 maintenance and fluid document (via NHTSA) - S4 quattro fluid specification
3. Audi of America, 2011 Audi Maintenance Schedule - All Models (via NHTSA) - brake fluid change every 2 years regardless of mileage; brake system and disc inspection items
4. Audi of America, 2011 Scheduled Maintenance Intervals (via NHTSA) - brake fluid replace every 2 years regardless of mileage
5. 49 CFR 571.116, FMVSS 116 Motor Vehicle Brake Fluids (Cornell LII) - DOT 3/4/5 dry and wet boiling points, fluid color requirements