Back in 1972, Subaru introduced the Leone 4WD Station Wagon. It was the first fourwheel drive vehicle designed specifically for everyday driving, rather than for off-road or rugged use.The safety and driving performance aspects of the Leone 4WD proved popular and made the car successful. It quietly set the standard for Subaru to become the global AWD leader of today.
Subaru Symmetrical All-Wheel Drive:
Subaru calls its system of mating a horizontally opposed (boxer) engine to various types of full-time AWD “Symmetrical All-Wheel Drive.” This system is based on the balance of both the powertrain and the straight, nearly-horizontal, flow of power to the wheels.The weight of the flat boxer engine and the transfer components lie very low in the chassis, providing a lower center of gravity, resulting in excellent traction and stability.
The Five Types of Subaru Symmetrical All-Wheel Drive:
Subaru currently uses five different types of Symmetrical AWD. Each is specific to the Subaru model and transmission.The five types are:
■ Continuous All-Wheel Drive
■ Active All-Wheel Drive
■ Variable Torque Distribution (VTD) All-Wheel Drive.
■ Driver Controlled Center Differential (DCCD) All-Wheel Drive
■ Vehicle Dynamics Control (VDC) All-Wheel Drive
The Environmental Protection Agency (EPA) now has regulations in place that establish requirements for on-board diagnostic (OBD-II) systems on light-duty vehicles and light-duty trucks. The purpose of the OBD-II system is to ensure proper emission control system operation for the vehicle’s lifetime by monitoring emission-related components and systems for deterioration and malfunction.
There’s a big difference between detecting only hard faults (OBD-I) and having the ability to actively monitor the system for proper operation, deterioration or a malfunction (OBD-II).
Engines in today’s vehicles are largely electronically controlled. Sensors and actuators sense the operation of specific components (e.g., the oxygen sensor) and actuate others (e.g., the fuel injectors) to maintain optimal engine control. An on-board computer, known as the “powertrain control module,” controls all of these systems.
The picture below of this paragraph shows the location of piston size and main journal size information on all Subaru engines. As the figure illustrates, it is possible to have more than one piston size in the same engine.
The importance of checking electrical ground connections during any electrical troubleshooting cannot be over stressed. For example, a poor electrical ground at the radiator support or fender (depending on the affected Subaru model) may cause any or all of the following problems:
• The door ajar indicator light dims when the brake pedal is applied.
• There is a loss of communication with the Automatic Transmission side of the New Select Monitor when the vehicle is put into gear.
• The engine starts running poorly after driving only a few feet.
• There is a loss of communication with the Anti-lock Brake side of the New Select Monitor when the brake pedal is applied.
Vehicles that have been involved in accidents should be inspected especially closely. In the example below, a Subaru Legacy had been involved in a front end collision.
During reassembly of the vehicle, the electrical ground wire behind the left front headlight that fastens to the radiator support had not been reinstalled (refer to photo). This electrical ground is attached to the left front fender on Subaru Impreza and Forester models. After reinstalling this ground wire, all of the affected systems returned to proper working order.
Subaru vehicles are more reliable than ever before. To assure their continued reliability, a schedule of inspection and maintenance (I & M) services is prescribed by Subaru of America for every Subaru vehicle sold. A copy of this schedule can be found in the Warranty and Maintenance Booklet located in the vehicle glove compartment.
Subaru vehicle maintenance inspections services are divided into recommended intervals beginning with three months or 3000 miles (whichever comes first). Each additional level in the maintenance schedule (7,500/15,000/ 30,000 miles) adds more maintenance and inspection steps to the process. The 15,000 (15 month) and 30,000 mile (30 month) services are ‘major’ services, and include the most comprehensive range of component checks, part replacements and adjustments.
If you are already familiar with Subaru vehicles, you may have developed a routine when performing a vehicle safety maintenance inspections. Following a set routine allows you to start at one end of the vehicle and end up at the other end, having performed all of the necessary safety inspection steps along the way.
Repetition of the safety inspection may also allow you to commit the steps to memory, but a checklist can be a helpful addition that leaves nothing to chance (or memory). Checking items off the checklist provides a written record that can be shared with the customer and retained for your service records as well.
Recommended steps in a Subaru Safety Maintenance Inspections are also spelled out in the owner’s Warranty and Maintenance Booklet. Some of the steps overlap services performed during the scheduled maintenance program. It could be argued that any scheduled maintenance should always include a Safety Inspection. Most of the Safety Maintenance Inspection steps are based on common sense, but it’s surprising how frequently these simple suggestions are ignored.
Wheel arch height (vehicle ride height) as well as front and rear wheel alignment should be inspected at 30 month/30,000 mile intervals. Winter driving and its attendant chuckholes may shorten that maintenance interval for some drivers
While inspecting wheel alignment, also check for obvious signs of damage to suspension components, tightness of bolts and nuts and the condition of other under car components.
Check, adjust and/or measure wheel alignment in accordance with the following procedures:
1.) Wheel arch height (front and rear)
2.) Camber (front and rear)
3.) Caster (front)
4.) Front toe-in
5.) Rear toe-in
6.) Thrust angle (rear)
7.) Wheel steering angle
1. Wheel Arch Height
1.) Adjust the tire pressures to specifications.
2.) Set the vehicle under “curb weight” conditions (empty luggage compartment, install spare tire, jack, service tools, and top off fuel tank).
3.) Set steering wheel in a wheel-forward position.
4.) Suspend a thread from the wheel arch (point “A” in figure above) to determine a point directly above the center of the spindle.
5.) Measure the distance between the measuring point and the center of the spindle.
6.) Consult the service manual for Wheel Arch Height specifications.
As we mentioned, it takes a special tool to work within the limited clearance area between the cylinder heads and the frame rails. The ST 498187 is a three part tool. One part wraps around the cam lobes, a second touches the outer edges of two shim buckets, and a third eccentric bolt exerts the necessary pressure to push a pair of shim buckets away from the cam lobe to make shim removal and replacement possible.
The tool installed in the three steps:
• Wrap the first half of the tool (part A) around the lobes.
• Attach the second half (part B) to part A by sliding its pins through the slotted holes in part A.
• Install the eccentric bolt (part C) into the hole in part A.
The eccentric bolt forces parts A and B away from one another. Because part A can’t move (it’s wedged against the cam lobes), the only thing that can move is part B. Part B moves by forcing the shim buckets downward, away from the camshaft.
The first versions of the 2.5 liter twin cam engines employed non-hydraulic valve actuation. Like the timing belt, the clearance between the engine valves and the shim and bucket valve actuators does not require inspection and/or adjustment until 105,000 miles have elapsed. However, various circumstances may require an adjustment before that milestone is reached.
Clearance is tight and there is little room to work between the cylinder heads and the left and right frame rails. A special tool (ST 49818700) is available for depressing the valves and removing the adjusting shims. Without this tool, the job is impossible to accomplish with the engine in the car. Once again, we had the benefit of working on an engine that had already been removed from the car. Before you can adjust the valves, the engine must be cold. Consult the service manual to determine the parts that will need to be moved or removed to make some room to work.
Unlike some overhead cam engines that require you to rotate the cam until each cam lobe is facing 180 degrees away from the adjustment shim, Subaru has very specific procedures for adjusting four valves at a time (a pair of intakes and a pair of exhausts). The pairs of intakes and exhausts are never for the same cylinder, which makes things rather interesting. This system requires you to turn the crankshaft a total of four times to complete the adjustment procedure.