Parts for your 2008 Subaru Impreza-Brake wheel cylinders

2008 Subaru Impreza brake wheel cylinders: fitment, function and service tips

Based on technical references used by Subaru dealers and repairers — the Subaru Impreza 2008MY GE/GH Factory Service Manual (Brake section), the Subaru FAST electronic parts catalogue (rear brake group), and market specification sheets for AU/NZ models — brake wheel cylinders are fitted only to 2008 Impreza variants with rear drum brakes. Many base-spec non-turbo models in Australia and New Zealand were supplied with rear drums, while WRX and higher trims run four-wheel discs. On disc-brake rears there are no wheel cylinders, hydraulic clamping is done by calipers, and the handbrake is a mechanical drum-in-hat that doesn’t use wheel cylinders.

For 2008 Impreza models with rear drums, the brake wheel cylinder is a compact hydraulic unit inside each rear drum. When the driver presses the pedal, brake fluid pressure pushes two small pistons outward, forcing the brake shoes against the drum to slow the car. Simple, robust, and effective, the little cylinder does a big job — and like any hydraulic part, it’s only happy when it’s clean, sealed and full of the correct fluid.

Common signs it’s time to check or replace the wheel cylinders include:

• Spongy pedal feel or the car pulling to one side under braking
• Wetness or dark staining on the lower edge of the backing plate or inside the drum
• Uneven rear shoe wear, low fluid level, or contamination on the brake shoes

Good practice for AU/NZ servicing is to inspect the rear drums and wheel cylinders every 20,000–30,000 kilometres or 12 months, or sooner if there’s any hint of a leak. Boots should be supple and intact, and there should be no seeping at the pistons. If a cylinder is leaking or sticking, replace it in axle pairs and fit new shoes if contaminated. Follow the Factory Service Manual for torque settings and bleeding order, and use the brake fluid grade specified on the reservoir cap (DOT 3 or DOT 4 per the FSM for the vehicle’s market). After reassembly, bleed until fresh, clear fluid and a firm pedal are achieved, then road test in a safe area.

Handy tips:

1. Confirm you actually have rear drums before ordering parts — a quick look through the rear wheel or a VIN-based parts lookup will do it.
2. Avoid twisting the brake hose, use a flare-nut spanner on the line fitting and support the cylinder while loosening.
3. If drums are off, measure drum ID and check shoe thickness, stay within the wear limits listed in the FSM.

Where a 2008 Impreza is fitted with rear discs, wheel cylinders aren’t used because the design relies on calipers for hydraulic braking and a mechanical parking-brake shoe assembly inside the rotor hat — no hydraulic actuation at the rear shoes, so no wheel cylinders to service.

Popular questions about 2008 Subaru Impreza brake wheel cylinders

Does my 2008 Impreza have rear drum brakes and wheel cylinders?
Many AU/NZ base-spec non-turbo models have rear drums (and therefore wheel cylinders), while WRX and higher trims have rear discs. Peek through the rear wheel: a smooth drum indicates drums, a visible caliper and rotor means discs. A VIN-based parts lookup or the Factory Service Manual will also confirm your setup.

How often should wheel cylinders be replaced?
There’s no fixed interval, they’re replaced on condition. Inspect at least every 20,000–30,000 km or 12 months. If there’s leakage, sticking pistons, damaged boots, or contaminated shoes, replace both rear cylinders as a pair and bleed the system with the specified fluid.

What brake fluid should be used after wheel cylinder work?
Use the grade printed on the reservoir cap or listed in the Brake section of the Subaru Factory Service Manual for your exact model — commonly DOT 3 or DOT 4. Don’t mix fluid types, and always use fresh fluid from a sealed container.