2008-2015 Scion XB Brake Fluid Type and Flush Interval

By Core Brake Parts Tech Team — Circleville, OH warehouse

Every 2008-2015 Scion xB uses DOT 3 brake fluid: the owner's manual lists the fluid type as FMVSS No.116 DOT 3 or SAE J1703. Scion's factory maintenance schedule does not list a fixed brake fluid replacement interval. Instead it calls for regular brake inspections, so the practical rule is simple: test the fluid at every brake inspection and flush it when it tests wet or looks dark, rather than waiting for the pedal to go soft.

What brake fluid the 2008-2015 Scion xB takes

The second-generation xB (the 2.4L 2AZ-FE model sold from 2008 through 2015) specifies one fluid for the whole brake system. The specifications page of the owner's manual lists SAE J1703 or FMVSS No.116 DOT 3, and the do-it-yourself maintenance section repeats it for topping off the reservoir. Manual-transmission cars use the same DOT 3 specification for the hydraulic clutch.

DOT 3 is a glycol-ether fluid defined by the federal brake fluid standard, FMVSS 116. That standard sets minimum boiling points and requires every container to carry a warning to keep it clean and tightly closed to prevent moisture absorption. The numbers matter because they explain why fluid wears out:

Stick with DOT 3 as the manual specifies. Never put silicone DOT 5 (the purple fluid) in an xB. It is a different chemistry from the glycol fluid the system was built around and is not what Scion calls for.

Why brake fluid needs changing at all

Glycol brake fluid is hygroscopic: it pulls moisture out of the air through the reservoir vent, hoses and seals. The xB owner's manual warns that excess moisture in the fluid can cause a dangerous loss of braking efficiency, and tells owners to use only newly opened fluid.

The wet boiling point in the table above is measured after the fluid has absorbed 3.7 percent water by volume, according to ADVICS, a major Japanese brake system maker. Notice how far DOT 3 falls: from 401 F dry to 284 F wet. ADVICS also points out that brake pads can run past 500 F in hard use, and that heat soaks into the caliper and fluid. If the fluid boils, it turns to vapor, and vapor compresses when you press the pedal. The result is a pedal that sinks toward the floor on a long downhill or after repeated hard stops.

Water in the fluid also corrodes metal parts from the inside: caliper pistons and bores, brake line walls, and the valves in the ABS and stability-control actuator. On an xB, where ABS, electronic brake-force distribution, brake assist, traction control and vehicle stability control are all standard, that actuator is the most expensive hydraulic part on the car.

Flush interval: what Scion says and what we recommend

Scion's 2008 xB Scheduled Maintenance Guide does not include a timed brake fluid replacement. It calls for a visual inspection of the brake pads and discs every 5,000 miles or 6 months, and an inspection of the brake lines and hoses every 15,000 miles or 18 months, checking for chafing, cracks, deterioration and leaks.

No fixed interval does not mean the fluid lasts forever. ADVICS says DOT 3 fluid typically needs replacement about once a year, while noting that the owner's manual is the final word. Most xBs on the road today are 10 to 18 years old, so if there is no record of a flush, assume the fluid is overdue. A practical approach:

• Test at every brake inspection. Use a brake fluid test strip or an electronic boiling-point tester at the reservoir.
• Flush when it tests wet or looks dark. The federal standard describes DOT 3 as colorless to amber. Brown or black fluid is contaminated.
• Flush any time the system is opened for calipers, hoses or a master cylinder, since fresh fluid is going in anyway.
• Shorten the interval if you tow, drive in the mountains, sit in heavy stop-and-go traffic, or live somewhere humid.

Symptoms of old or low brake fluid on an xB

• Soft or sinking pedal that firms up when you pump it, or fades after repeated stops. This is classic moisture or air in the fluid.
• Brake system warning light. On the xB this light covers both low brake fluid and a brake system malfunction, and it also comes on when the parking brake is set. If it stays on after the parking brake is fully released, check the fluid level right away.
• Fluid level dropping. The manual notes it is normal for the level to fall slightly as the pads wear. If the reservoir needs frequent refilling, there may be a serious problem such as a leaking caliper, hose or master cylinder.
• Dark, cloudy fluid in the see-through reservoir.

To check the level, look at the reservoir under the hood. The fluid should sit between the MAX and MIN lines. On the second-generation xB you release the clips on the service cover to reach the reservoir cap.

How the flush is done and what to replace at the same time

A flush pushes new DOT 3 through each wheel's bleeder screw until clean fluid comes out, keeping the reservoir from running dry so no air enters. Wash any spilled fluid off paint immediately, because the manual warns that brake fluid damages painted surfaces. Torque the bleeder screws to the value in the factory service manual. If air ever gets into the ABS and stability-control actuator (for example, if the reservoir ran empty or the master cylinder was replaced), the factory procedure uses a scan tool to cycle the actuator while bleeding. That job is best left to a shop with the right tool.

For a driveway mechanic with a helper or a one-person bleeder, a basic flush is a moderate job of about an hour. Brake work is the ideal time to do it, because the wheels are already off:

• Worn pads and rotors: the 2008-2015 Scion xB front and rear brake kit covers all four corners, since the xB has disc brakes at both ends. You can also browse replacement brake pads and brake rotors.
• Sticking or leaking calipers: a stuck piston is often the long-term result of wet fluid. See our brake calipers.
• Cracked or swollen rubber hoses found at inspection: see brake hoses.
• Clips, shims and slide pins: a brake hardware kit keeps new pads quiet and sliding freely.

Frequently Asked Questions

What type of brake fluid does a 2008-2015 Scion xB use?

DOT 3. The owner's manual specifies FMVSS No.116 DOT 3 or SAE J1703 brake fluid. Use a fresh, sealed bottle.

How often should I flush the brake fluid on my Scion xB?

Scion's maintenance schedule has no fixed replacement interval, only regular brake inspections. Test the fluid at each inspection and flush it when it tests wet or looks dark. ADVICS says DOT 3 is typically due about once a year, and any xB with no flush on record is overdue.

Can I use DOT 4 in my Scion xB?

DOT 4 is also a glycol-based fluid with higher boiling points, but Scion specifies DOT 3. The safest choice is the fluid the manual calls for. Never use silicone DOT 5.

Why does my xB brake warning light stay on?

The light comes on for low brake fluid, a brake system malfunction, or a parking brake that is not fully released. If it stays on with the parking brake released, check the reservoir level and have the brakes inspected before driving further.

Is it normal for the brake fluid level to drop?

A slight drop as the pads wear is normal. If you have to keep adding fluid, something is leaking and the car needs an inspection.

Should I change brake fluid when I replace pads and rotors?

It is a good time to do it. The wheels are already off, the bleeders are easy to reach, and the new fluid goes in while the system is already being worked on.

Sources

1. Scion xB Owner's Manual (OM12F03U) - DOT 3 / SAE J1703 fluid spec, 2AZ-FE engine, moisture warning, MAX/MIN level, warning light, paint caution
2. 2008 Scion xB Scheduled Maintenance Guide - pad/disc inspection every 5,000 miles, lines and hoses every 15,000 miles, no timed fluid replacement
3. 2013 Scion xB Quick Reference Guide - standard ABS, EBD, brake assist, VSC and traction control
4. 2008 Scion xB Review, The Auto Channel - front vented discs, rear solid discs, 2.4L engine
5. 49 CFR 571.116 (FMVSS 116), Cornell LII - DOT 3/4/5 dry and wet boiling point minimums, container moisture warning, fluid colors
6. ADVICS: Brake Fluid Boiling Points - 3.7 percent water wet boiling point, hygroscopic fluid, vapor lock, DOT 3 replacement guidance