There are three types of power-steering systems today. This video is sponsored by The Group Training Academy.
Mileage is an essential criterion for evaluating the condition of brake hydraulics. Keep in mind that, each time the brakes are applied, the master and wheel cylinder piston seals wear. Given time, the rubber cups in master cylinders wear to the point that they will not consistently seal hydraulic pressure. The result will often be a low brake pedal, poor stopping power or an intermittently sinking brake pedal.
During a service writer’s efforts to sell competitive brake services at the service desk, he or she often focuses on selling “good, better or best” brake friction replacements, while ignoring the added expense of repairing brake hydraulics. Unfortunately, neglected brake hydraulic systems can cause an expensive warranty comeback or, even worse, a serious traffic accident. In any case, it’s important to advise a potential customer of the importance of servicing and repairing worn brake hydraulics.
Hydro-boost brake systems are self-bleeding if there is no other problem in the system. Use this initial bleeding procedure whenever replacing or servicing any component in a hydro-boost system. Normal driving conditions will remove air that remains trapped within the system when components are properly installed and there are no flow restrictions in the system. Always refer to the vehicle service manual for specific installation and testing procedures on import and domestic vehicles.
Some vehicles may exhibit a low or spongy pedal after wheel end brake service that cannot be remedied by bleeding the brakes. This may be due to a prematurely deteriorated seal in the master cylinder. Remove snap ring and rearmost piston from master cylinder to inspect seals. If any deformation or deterioration of seals is present, replace the master cylinder.
Some owners may complain of a squeaking noise when applying or releasing the brake pedal. According to Saab, the problem is contaminated brake fluid. The contaminated fluid may swell the master cylinders piston seals.
Anti-lock brake systems (ABS) and the HCU are replacing proportioning, combination and other valves to change the braking forces in the front and rear. This is called Electronic Brake Distribution (EBD) and it can dynamically change to proportioning to take into account if the vehicle is turning or is loaded. The system can also use EBD to perform a “soft stop.” This routine is performed when a vehicle is slowing at low speeds and the brake force is varied in the front and rear so the vehicle’s attitude is controlled and weight is evenly transferred. This means a flatter and more stable stop.
Brake hoses are the most government-regulated components on a vehicle. Anyone making brake assemblies must be registered with the Department of Transportation (DOT). All aftermarket hose, fittings and complete hoses must conform to FMVSS 106 and SAE J1401. These tests are demanding and often exceed what a vehicle will see in the real world.
Although four-wheel disc brakes currently dominate the import brake service market, millions of drum brakes are serviced each day in independent import shops. Thanks to their age, many drum brakes present problems related not only to normal wear, but also to extended age and mileage.
The ABS computer or HCU is a node on a high-speed vehicle bus. This means that the information can be typically accessed through the OBDII DLC. The ABS controller/modulator is the heart of any ABS or ESC system. The modulator gets the brake pressure from the master cylinder. Inside are the valves and solenoids that control the pressures to the wheel. During normal operation, the pressure from the master cylinder goes through the HCU unaltered.
The 2006-current Cadillac DTS is the largest sedan that General Motors offers. The DTS incorporates the K-platform as denoted by the 4th letter in the VIN. It is built on the same line as the Buick Lucerne. The two vehicles share many brake components, but option packaging is different for the Lucerne.