Gene Markel, Author at UnderhoodService
Diesel Particulate Filters

The EPA has lowered diesel fuel sulfur ­content from 500 ppm (parts per million) to 15 ppm. This new ultra-low sulfur fuel has been available since October 2006. All 2007 and later diesel engines must comply with the new regulations that require the reduction of nitrogen oxide (NOx) and hydrocarbons (HC) by 50% and particulate

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.

BRAKE JOB: GM Acadia / Buick / Outlook / Enclave

The Lambda Platform is shared with the Chevrolet Traverse, Saturn Outlook, GMC Acadia and Buick Enclave. It is largely derived from the GM Epsilon platform, the same platform that makes the Chevrolet Malibu and Pontiac G6. These vehicles can be front- or all-wheel drive. All models have the same rear disc brake setup with the parking brake in the hat of the rotor. All Lambda platform vehicles incorporate Tire Pressure Monitoring (TPMS) ABS and Stabilitrak electronic stability control.

Bleeding ABS Brake System: Why Brake Fluid and Lines Degrade

According to R. L. Polk, the average age of the vehicles on U.S. roads was 9.2 years in 2007 with 41 percent of the vehicles 11 years or older. This high median age is a good reason to consider the condition of the brake fluid and bleeding procedures when performing maintenance or repairs. Maintenance or repair of an Anti-lock Brake System (ABS) system can require the opening of the hydraulic system. Any time the hydraulic system is opened, air can be introduced into the lines and components.

Nivomat Shock Absorbers: Self-Leveling Monotube Ride Control Units

The Nivomat Shock Absorber is a self-leveling monotube shock absorber developed by Sachs. Nivomat shocks are used by Chrysler, Ford, General Motors, Jaguar, Kia, Mitsubishi, Saab, Volvo and other OEMs. The system is also available on the GM Suburban and Tahoe as part of ZW7 Premium Smooth Ride Suspension. Replacement units are available from Monroe, ZF Sachs and OES suppliers.

Tech Feature: Servicing Diesels in Your Shop

Is there a diesel in your service bay? Maybe not now, but there definitely will be in your future. You’re going to see trucks as well as SUVs and passenger cars. Mercedes-Benz produced a 3.0L V6 diesel-powered SUV for the 2008 model year and Volkswagen has a Twinturbo 5.0L V10 diesel engine in its Touareg. As the automakers focus on better fuel economy, you might say the diesels are coming again.

TPMS: Tire Pressure Monitoring Service for All Shops

Recently, an owner of a 2008 Lincoln Navigator brought their vehicle in for a tire rotation. The tires were rotated front to rear. The customer drove away not knowing he was in great peril. A few days later, the right rear picked up a small leak. The TPMS system turned on the dashlight and indicated

Tech Tip: Priming a New Master Cylinder

Priming in less time.