2006-2011 Acura CSX Brake Fluid Type and Flush Interval

By Core Brake Parts Tech Team — Circleville, OH warehouse

The 2006-2011 Acura CSX uses DOT 3 brake fluid. Acura and Honda specify their own Heavy Duty Brake Fluid DOT 3, allow a DOT 3 or DOT 4 fluid from a sealed container only as a temporary top-up, and warn that DOT 5 will damage the system. Replace the fluid every 3 years, no matter what the dash maintenance display shows or how few miles the car has covered.

The CSX was sold only in Canada and built at Honda of Canada Manufacturing in Alliston, Ontario, so a lot of owners end up reading Honda Civic sedan paperwork from the same era. For brake fluid that is fine: the 2009 Civic Sedan owner's manual and Acura's own owner information give the same instructions, and they are summarized below.

What brake fluid the Acura CSX takes

Honda's owner's manual for this generation is direct about it: always use Heavy Duty Brake Fluid DOT 3. If that is not available, use only DOT 3 or DOT 4 from a sealed container, and treat it as a temporary replacement. The manual goes further and says non-Honda fluid can cause corrosion and shorten the life of the system, and it recommends having the system flushed and refilled with the Honda DOT 3 fluid as soon as possible after using something else. Acura's owner information carries the same recommendation under the Acura name (Acura Heavy Duty Brake Fluid DOT 3).

If your CSX has a manual transmission, the clutch hydraulic system uses the same fluid as the brakes, per the owner's manual. That matters when you flush: an old clutch circuit full of wet fluid is easy to forget.

Why DOT 3 and not DOT 5

DOT 3, DOT 4 and DOT 5.1 are all glycol-based fluids. DOT 5 is silicone-based, and it does not belong in a system designed around glycol fluid and the seals that go with it. That is why both Honda and Acura print the same warning: brake fluid marked DOT 5 is not compatible with the braking system and can cause extensive damage. DOT 5.1 is a different product from DOT 5 despite the similar name; it is glycol-based. Even so, the factory spec for the CSX is DOT 3, and the manual only allows DOT 4 as a stopgap, so there is no reason to go looking for anything more exotic on a street-driven car.

The DOT minimums show why fluid choice and fluid age both matter. DOT 3 must have a dry boiling point of at least 401 F and a wet boiling point of at least 284 F. DOT 4 must reach at least 446 F dry and 311 F wet. The wet figure is measured after the fluid has absorbed 3.7 percent water by volume, which is the condition old fluid in a daily driver works its way toward.

Why the interval is time-based: 3 years

Glycol brake fluid is hygroscopic, meaning it pulls moisture out of the air around it. It does this whether the car is driven 5,000 km a year or 40,000. As water content climbs, the boiling point falls toward that wet rating, and water in the system also promotes internal corrosion in calipers, the master cylinder and the ABS hydraulic unit.

That is why Honda does not tie brake fluid to mileage on this generation. The Maintenance Minder in the 2006-2011 Civic sedan manual lists service codes for oil, tire rotation, filters, transmission fluid, spark plugs, valves and coolant, but brake fluid is handled separately in a note: independent of the maintenance message in the information display, replace the brake fluid every 3 years. In other words, the dash will never remind you. Write the date on a tag near the reservoir or in your service log.

A car that sees spirited driving or occasional track days, which some Type S owners do, benefits from shorter intervals because heat cycles and fluid temperatures are much higher. For normal driving, 3 years is the factory number.

Symptoms of old or low fluid

• Soft or sinking pedal after hard use. Moisture-laden fluid can boil in the calipers during long descents or repeated hard stops, creating vapor that compresses.
• Dark fluid in the reservoir. Fresh DOT 3 is light amber and clear. Brown or cloudy fluid is overdue. Color alone does not measure water content, so go by the date if you have it.
• Level at or below MIN. The manual says the level should sit between MIN and MAX. A falling level usually means the pads have worn or there is a leak, and the manual says to have the system inspected rather than simply topping up.
• Brake system indicator on while driving. Honda's manual says this most likely means low fluid. Press the pedal lightly to check that it feels normal, check the level at your next stop, and have the system inspected for leaks or worn pads. If the ABS indicator comes on together with the brake system indicator, have the car inspected immediately.

Flushing the fluid and what to do at the same time

A proper flush replaces the fluid in the reservoir, lines, calipers and ABS unit, not just what is in the reservoir. The usual approach is to remove most of the old fluid from the reservoir, refill with fresh DOT 3 from a sealed bottle, then bleed each corner until clean fluid comes out, never letting the reservoir run low enough to draw in air. Follow the bleed sequence and any ABS-related steps in the factory service information for your car. On manual-transmission cars, bleed the clutch circuit too.

Because the wheels are already coming off for the flush, it is the right time to look at pads and rotors. The CSX has four-wheel disc brakes, so check both ends. If the front pads are near the wear limit, replacing them now means the caliper pistons are pushed back once and bled once. Options that fit include EBC Redstuff ceramic front pads for the 2007-2011 CSX Type S and EBC Greenstuff 2000 front pads for the CSX Type S. For rotors, base 2.0L cars take the EBC BSD7116 slotted front rotors and the EBC BSD7345 rear rotor set, while the Type S uses the EBC GD1473 front rotors. Confirm your trim before ordering, since base and Type S front brakes use different part numbers.

Also inspect the rubber brake hoses for cracks or bulging while you are there; Honda's B service calls for inspecting brake hoses and lines, including the ABS lines. Replacement hoses are in our brake hoses collection, and caliper slide pins and clips are in brake hardware kits.

How hard is the job

A fluid flush on the CSX is a moderate DIY job. You need a way to lift the car safely, the correct wrench for the bleeder screws, clear tubing and a catch bottle, and a helper or a one-person bleeder. Buy more fluid than you think you need, and always open a fresh, sealed bottle. Brake fluid damages paint, so cover the fenders and wipe up any spill immediately. If the pedal feels soft after bleeding, air is still in the system, and the car should not be driven until the pedal is firm. If you are not confident bleeding brakes, have a shop do it; the job costs little compared with the calipers and ABS unit it protects.

Frequently Asked Questions

Can I use DOT 4 in my Acura CSX?

The owner's manual allows DOT 3 or DOT 4 from a sealed container as a temporary replacement when the Honda or Acura Heavy Duty DOT 3 fluid is not available. It recommends returning the system to Heavy Duty DOT 3 afterward.

Can I use DOT 5 brake fluid?

No. Both Acura and Honda warn that fluid marked DOT 5 is not compatible with the braking system and can cause extensive damage. DOT 5 is silicone-based, unlike the glycol-based DOT 3 the car was designed for.

How often should the CSX brake fluid be changed?

Every 3 years. The Maintenance Minder on this generation does not show a brake fluid code, so the interval is time-based and you have to track it yourself.

Why does my brake fluid level keep dropping?

As pads wear, the caliper pistons move outward and more fluid sits in the calipers, so the reservoir level drops slowly. A sudden or large drop points to a leak. Either way, the manual says to have the brake system inspected rather than just adding fluid.

Does the clutch use brake fluid?

On manual-transmission models, yes. The owner's manual says to use the same fluid specified for the brake system in the clutch hydraulic system.

Should I replace pads and rotors when I flush the fluid?

Only if they need it, but a flush is a good time to measure them since the wheels are off. Browse brake pads and brake rotors if yours are near the limit.

Sources

1. Honda - 2009 Civic Sedan Owner's Manual - Heavy Duty DOT 3 spec, DOT 3/DOT 4 temporary use, DOT 5 warning, 3-year replacement independent of the display, monthly level check, clutch uses brake fluid, brake system indicator guidance, B-service hose and line inspection
2. Acura Canada - Owner's Manual: Brake Fluid - Acura Heavy Duty Brake Fluid DOT 3 recommendation, MIN/MAX level guidance, DOT 5 incompatibility
3. Honda Global - Exclusive to Canada Acura CSX news release - Canada-only model, built in Alliston, Ontario, four-wheel disc brakes
4. Tilton Engineering - Brake Fluid: Stay Safe and Go Fast - DOT 3 and DOT 4 minimum dry and wet boiling points, glycol vs silicone chemistry, hygroscopic behavior
5. ADVICS - Brake Fluid Boiling Points - wet boiling point defined at 3.7 percent water by volume, glycol-ether fluid absorbs moisture from the air