1991 GMC Jimmy Brake Wheel Cylinder Replacement Cost

The wheel cylinder functions by use of hydraulic pressure supplied by the master cylinder. When the wheel cylinder receives this pressure, both ends are pressed outward, forcing the brake shoes into the brake drum. The brake drum rotates with the wheel, so the hydraulic pressure from the wheel cylinder is transferred to the shoes, then the brake drum, and ultimately slows or stops the tires.

Brake wheel cylinder failure occurs in two different ways, with two opposite symptoms. The wheel cylinder can become seized, in which case it will not release the brake shoes from the rotor. The seized cylinder will cause the vehicle to brake constantly on one side of the vehicle, forcing the vehicle to move toward that side. Also, this pulling will be accompanied by a strong odor from one wheel. Another way wheel cylinders fail is by leaking. If there is a leak, the brake pedal will be noticeably easier to push, and will sink all the way to the floor when held. After only a few repetitions of pressing the brake pedal, the braking ability of the vehicle may become completely compromised. There may also be brake fluid leaking onto the wheel.

It is not safe to operate any vehicle with any braking problem. If there is any sign that the brakes are not performing as originally intended, the vehicle should immediately be placed out of service, and repaired.

Wheel cylinder failure on some vehicle's is more frequent than others. On most vehicle's, they will need replacement at some point. It is most common to replace wheel cylinders on vehicle's with over 75,000 miles.

Upon a visual inspection, the servicing technician will notice the brake shoes are severely worn on one wheel, the wheel cylinder does not provide sufficient clamping force to stop the vehicle, or brake fluid leaking out of the brake drum. The wheel cylinder in question will be inspected to verify a reliable diagnosis has been reached.

Replacement requires removal of the wheel and tire, brake drum, brake shoe hardware, and brake shoes. Then the brake line is disconnected from the wheel cylinder, and the cylinder is unbolted and removed. Once the new wheel cylinder is installed the brake shoes, brake shoe hardware, brake drum, and wheel are installed. The brakes will then be flushed, bled of air, and adjusted prior to placing the vehicle on the ground and tightening the wheel nuts to proper specifications.

When a wheel cylinder fails, the brake shoe friction linings on that wheel may become contaminated with brake fluid, or worn excessively. This will require replacement of the brake shoes, brake shoe hardware, and brake drum, through the drum may be eligible for resurfacing. Although the corresponding brakes on the other side of the vehicle may not have been affected, the shoes on both sides of the vehicle must be replaced, along with the brake drums to maintain even braking from side to side. If the faulty wheel cylinder is in the front of the vehicle, the rear brakes do not require replacement. Likewise, if the faulty wheel cylinder is in the rear, the front brakes do not require replacement unless faulty.

Drum brake systems vary from vehicle to vehicle, and the amount of braking force they can apply to the wheels is dependent on the level of performance demanded by the manufacturer. If the vehicle is very heavy, or performance oriented, the brake drums, shoes, and wheel cylinders may be much more expensive. Some drums must be replaced, but others may be resurfaced. Resurfacing is typically more cost effective.

The braking system can be maintained by a DIYer with a complete knowledge of hydraulically actuated systems. This is important as testing brake operation, and safe installation of braking components rely on this knowledge. If the complete braking system is not understood, damage to the expensive braking components or injury is likely. Trusting a professional technician with the replacement of any braking component is normally the best course of action.