2008-2015 Scion XB Brake Caliper Problems and Replacement

By Core Brake Parts Tech Team — Circleville, OH warehouse

On a 2008-2015 Scion xB, most caliper trouble comes down to one of three things: sticking slide pins, a piston that hangs up in its bore, or a leaking seal. The usual signs are a pull to one side, one wheel much hotter than the others, and one pad worn far thinner than its partner. The fix is either servicing the slide pins and hardware or replacing the caliper, ideally in axle pairs, and then bleeding the system.

How the Brakes on the Second-Generation xB Are Built

The second-generation xB (2008-2015) is a bigger, heavier car than the boxy first-generation model. It uses the 2.4-liter 2AZ-FE four-cylinder, and period road tests list a curb weight of about 3,020 lbs. To stop that weight, Scion fitted four-wheel disc brakes as standard: vented discs up front and solid discs at the rear, with ABS, electronic brake-force distribution (EBD), Brake Assist, vehicle stability control (VSC) and traction control (TRAC) on every car.

That matters for caliper work in two ways. First, there are no rear drums on this car, so there are four calipers to keep healthy, not two. Second, the stability and ABS systems share the same hydraulic circuit, so any caliper replacement has to finish with a thorough bleed to keep a firm pedal.

The front calipers are floating calipers that slide on two pins in a mounting bracket. Toyota lists them as a left and right pair (47750-12A70 driver side and 47730-12A70 passenger side for the 2.4-liter 2AZ-FE xB). The rear calipers work the same way. Because the caliper floats, the piston pushes the inner pad and the caliper body slides back on its pins to pull the outer pad in. If those pins stop sliding, the whole design stops working as intended.

Symptoms of a Bad Caliper on a Scion xB

Caliper problems tend to show up gradually. Watch for these:

• Pulling to one side under braking or while cruising. A caliper that drags or does not apply fully makes the car pull.
• One hot wheel. After a drive, a dragging brake leaves that wheel noticeably hotter than the others, often with a burning smell.
• Uneven pad wear. The inner pad worn to the backing plate while the outer pad still has life, or the reverse, points straight at binding pins or a sticky piston.
• Pad noise and fast pad wear. ADVICS, an OE brake supplier with ties to the Toyota Group, lists brake pad noise and excessive pad wear as the symptoms of a sticking slide pin.
• Soft pedal or fluid on the inside of the wheel. A leaking piston seal or bleeder lets fluid out and air in. This is a stop-driving problem.
• Clunk or rattle over bumps. Worn pin boots and sleeves let the caliper knock in its bracket.

What Causes xB Calipers to Stick

These cars are now 10 to 17 years old, and many live where roads are salted. Age and corrosion are the main enemies:

• Dry, rusted slide pins. Once the grease is gone, the pin corrodes in its bore. ADVICS names a slide pin rusted from running out of grease as a primary cause.
• Damaged boots and sleeves. Heat and friction crack the rubber boots and sleeves over the pins. Water gets in and the pin seizes.
• Bent pins or worn bracket surfaces. Brake and Front End notes that bent or binding mounting pins, worn sliding surfaces, damaged brackets and swollen or hardened guide seals all stop a floating caliper from moving freely.
• Wrong grease. Petroleum-based grease swells rubber boots and sleeves until they grip the pin. Use only a high-temperature caliper lubricant made for brakes.
• Corroded piston. Moisture in old brake fluid and a torn dust boot let rust form on the piston, so it retracts slowly or not at all.

Diagnosing It Before You Buy Parts

You do not need to guess. With the car safely supported and the wheel off:

1. Spin the wheel by hand. A light pad whisper is normal; a wheel that is hard to turn is dragging.
2. Remove the caliper from the bracket and pull each slide pin. It should slide in and out by hand with smooth, even resistance. If it will not move, moves in jerks, or springs back out, it needs service.
3. Check the pin boots and the piston dust boot for tears, cracks or swelling.
4. Look for wetness around the piston and the bleeder. Any fluid leak means the caliper gets replaced, not greased.
5. Compare inner and outer pad thickness on both sides of the axle.

The Fix: Servicing vs Replacing the Caliper

If the piston and seal are healthy and only the pins are sticking, a full hardware service can bring the caliper back. Clean the pin bores, fit new pins, boots and clips from a brake hardware kit, and lubricate every sliding surface with high-temperature caliper grease. Brake and Front End recommends renewing all mounting hardware during the repair.

If the piston is seized or leaking, replace the caliper. Many replacement brake calipers for the xB come loaded with the bracket, which saves you from fighting a rusted bracket and pins. Replace calipers in pairs across the axle so both sides clamp the same.

A few job notes:

• Match left and right carefully. The bleeder must point up after installation or you will never get the air out.
• Use a new copper crush washer on each banjo fitting.
• Torque the bracket bolts, pin bolts and banjo bolt to the values in the factory service manual.
• Refill with the brake fluid specified on the reservoir cap and in the owner's manual, and never reuse old fluid.
• Bleed each wheel until the fluid runs clear and bubble-free. If the pedal still feels soft on a VSC-equipped car, a shop can cycle the ABS actuator with a scan tool during bleeding.

What to Replace at the Same Time

A dragging caliper usually cooks the pads and rotor it has been rubbing. Inspect both. If the pads are glazed, cracked or unevenly worn, fit new brake pads. If the rotor shows heat spots, a lip, grooves or runout, replace it too. For many owners the simplest path is the 2008-2015 Scion xB front and rear brake kit, which covers pads and rotors on both axles in one order. It is also a good moment to check the flexible brake hoses: a hose that has collapsed inside can hold pressure on a caliper and mimic a stuck piston.

The TRD Big Brake Kit Recall

If your xB wears the optional Toyota Racing Development front brake kit, check your recall status. Toyota filed Safety Recall J0U (NHTSA 18E-091) in September 2018 because the brake hoses supplied with the front TRD brake kit designed for 2008-2015 xB and 2011-2016 tC could become damaged over time and reduce braking performance. The remedy is replacement with the standard equipment brake kit at a Toyota dealer. Factory-brake cars are not affected, but a used xB with aftermarket-looking front calipers deserves a VIN check.

Frequently Asked Questions

Do I need to replace both calipers if only one is bad?

It is strongly recommended. Both calipers on an axle have the same age and exposure, and a new caliper on one side and a tired one on the other can cause a pull. Replacing in pairs keeps braking even.

Does the 2008-2015 Scion xB have rear disc brakes?

Yes. The second-generation xB came with four-wheel disc brakes: vented discs in front and solid discs in the rear, with ABS, EBD and Brake Assist.

Can I just grease the slide pins instead of buying a caliper?

Often, yes. If the pins are the problem and the piston is not leaking or seized, cleaning the bores and fitting new pins, boots and brake-rated grease fixes it. A leaking or seized piston means a new caliper.

Why is my xB pulling to one side after a brake job?

The usual causes are a sticking pin or piston on one side, a collapsed brake hose, air in one line, or contaminated pads. Check for a hot wheel and uneven pad wear on each side to find which caliper is at fault.

Is caliper replacement a DIY job on the xB?

For someone with basic tools, a torque wrench and a way to bleed the brakes, yes. It is a bolt-on job. The critical parts are correct left and right placement, new crush washers, proper torque and a complete bleed.

Is my xB part of a brake recall?

Only if it has the optional TRD front brake kit covered by Safety Recall J0U. Enter your VIN on the NHTSA recall lookup or ask a Toyota dealer to confirm.

Sources

1. Toyota Safety Recall J0U remedy notice (NHTSA 18E-091) - TRD brake kit brake hose recall for 2008-2015 xB and 2011-2016 tC
2. Toyota Parts Deal: 2008 Scion xB brake caliper - OE front caliper numbers 47750-12A70 and 47730-12A70 for the 2AZ-FE xB
3. The Auto Channel: 2008 Scion xB review - vented front and solid rear discs, ABS, EBD, BA, VSC, TRAC standard, 2.4L engine, curb weight
4. ADVICS: Troubleshooting caliper slide pin sticking - symptoms, causes and fixes for sticking slide pins
5. Brake and Front End: Bent or binding mounting pins - causes of floating caliper binding and hardware renewal advice