Drum Brake Self Adjusters
In some cases, the master cylinder may contain residual check valves to prevent air from being drawn past the wheel cylinder cup seals when the shoes are retracted by the return springs.
Scrub Radius And Alignments
Big rims or tires can look good and give a vehicle a unique appearance. But it’s what you can’t see that can become really ugly, especially if the alignment and suspension angles have become altered in the installation process.
Power Steering Dynamics And Diagnostics
Twenty-five years ago, when the power steering failed, diagnosing the system was easy. The most difficult problem to diagnose was the “morning sickness” that plagued some vehicles when they were cold. Today, the introduction of speed sensitive steering, electric power steering and computer controls have made power steering diagnostics more demanding.
Electric Power Steering Diagnostics
Electric power steering is more energy efficient than hydraulic systems and does not provide assist until it receives driver input, but there are differences in the hydraulic and electric assist that will affect the driver’s and technician’s understanding of the component and its integration into the ESC and self-park system.
Oxygen Sensors: Pulse Measurement
Watching an oxygen sensor output on an oscilloscope is like watching a sporting event on television. You get to see the action, but can do nothing about it as it happens. Sometimes you miss the action and want an instant replay. It was a bad call. You saw the interference. If the referee didn’t see
Servicing Corroded Drums and Rotors
In the Northeast and Midwest, a flat tire and an alloy wheel seizing on the hub (two parts jammed or stuck) is a common occurrence caused by corrosion. Corrosion and rust are nasty problems that make repairing a vehicle difficult. Corrosion is the product of an electrochemical reaction, in a vehicle’s case, between two dissimilar
Electronic Power Steering: A Change In Technology
An Electronic Power Steering (EPS) system’s advantage over a hydraulic system is if the engine stalls, you will still have steering assist. This advantage can also be a disadvantage if the system should shut down while the engine is running because if the engine stalls, you lose steering assist. A driver unaware of this condition
Servicing Wheel Bearings And Wheel Speed Sensors
If you are replacing a wheel bearing on a late-model vehicle, you will be dealing with a wheel speed sensor. In the past decade, wheel speed sensors have been moving from differentials, axles and knuckles to inside or on the wheel bearing or hub unit. At this location, the sensors are more accurate and often more protected from the elements.
ABS/ESC: Hydraulic Control Unit/Modulator Diagnostics
Under normal braking conditions, the master cylinder supplies fluid to the HCU and routes the pressure to the calipers. The solenoids are not energized allowing fluid to pass directly from the master cylinder to the caliper. The top solenoid is an isolation valve that isolates the HCU from the master cylinder during stability control interventions;
Tech Feature: Electric/Electronic Parking Brakes
The current emergency/parking brake is the most unused device on a vehicle equipped with an automatic transmission. But, the electrically actuated parking brake is changing the parking brake into a multi-purpose mechanism on modern vehicles. Using an electric motor to apply the parking brake results in the mechanical linkage being eliminated from the vehicle passenger compartment.
Planetary Gears 101
The most confusing systems on any car is the automatic transmission. The main stumbling block for most technicians is not the electronic control systems, but the humble planetary gear. The planetary gear sets in an automatic transmission provide forward underdrive and overdrive gear ratios, plus reverse. The machinery handbook describes planetary gearing as a compact means of driving inline shafts with speed reduction (underdrive) and induction (overdrive).
Advantages of planetary gears over parallel axis gears include high power density, large reduction in a small volume, pure torsional reactions and coaxial shafting. Disadvantages include high bearing loads, inaccessibility and design complexity. The planetary gearbox arrangement is an engineering design that offers many advantages over traditional gearbox arrangements. One advantage is its unique combination of both compactness and outstanding power transmission efficiencies.
Wheel Speed Sensors: ABS and TCS Signal Use
The signals from the Wheel Speed Sensors (WSS) are the most important sensor input to the Brake Control Module (BCM) for ABS activation.