Engine Mechanical - 3.0L: Other Mazda Tribute II

ENGINE - 3.0L

The 3.0L is a V-6 engine that has the following features

1. Dual overhead camshafts
2. Four valves per cylinder
3. Sequential Multi-Port Fuel Injection (SFI)
4. Composite lower intake manifold and composite upper intake manifold
5. Aluminum cylinder heads
6. 2-piece aluminum cylinder block
7. Variable Camshaft Timing (VCT) system
8. Electronic ignition with 6 ignition coils

Exhaust Emission Control System

For operation and required maintenance of the exhaust emission control devices used on this engine, see ENGINE EMISSION CONTROL - 2.5L AND 3.0L .

Induction System

The SFI provides the fuel/air mixture needed for the combustion in the cylinders. The 6 solenoid-operated fuel injectors

1. Are mounted between the fuel rail and the intake manifold.
2. Meter fuel into the air intake stream in accordance with the engine demand.
3. Are positioned so that their tips direct fuel just ahead of the engine intake valves.

Valve Train

The camshafts are mounted in the cylinder heads and act against a roller follower to open and close the valves. A hydraulic lash adjuster is located on one side of the roller follower and the valve tip on the opposite end. The camshafts are driven off the front of each cylinder head by 2 chains (one each side). Both of the chains are driven by sprockets that are located on the crankshaft, just in front of the oil pump.

Variable Camshaft Timing (VCT) System

The VCT system changes intake camshaft timing dependent on engine speed, load and oil temperature. Oil pressure advances and retards camshaft timing to improve low-speed and high-speed engine performance, engine idle quality and exhaust emissions.

Positive Crankcase Ventilation System

All engines are equipped with a closed-type positive crankcase ventilation system recycling the crankcase vapors to the upper intake manifold.

Oil Pump

The lubrication system is designed to provide optimum oil flow to critical components of the engine through its entire operating range.

The heart of the system is a positive displacement internal gear oil pump.

Generically this design is known as a gerotor pump, which operates as follows

1. The oil pump is mounted on the front face of the cylinder block.
2. The inner rotor is piloted on the crankshaft post and is driven through flats on the crankshaft.
3. System pressure is limited by an integral internally-vented relief valve which directs the bypassed oil back to the inlet side of the oil pump.
4. Oil pump displacement has been selected to provide adequate volume to make sure of correct oil pressure both at hot idle and maximum speed.
5. The relief valve calibration protects the system from excessive pressure during high viscosity conditions.
6. The relief valve is designed to provide adequate connecting rod bearing lubrication under high-temperature and high-speed conditions.

Cooling System

The engine cooling system includes the following

Scheme 623

1. Radiator
2. Dual electric fan assemblies
3. Degas bottle (aids in maintaining the correct volume of engine coolant)
4. Coolant thermostat
5. Coolant hoses
6. Coolant pump housing

Accessory Drive

The accessory drive

1. has a single serpentine belt with 6 ribs.
2. has an automatic drive belt tensioner.
3. has a 3-ribbed water pump belt.

The accessory drive system provides power to operate components which power other systems. These could include components such as the generator, power steering pump and A/C compressor. Each of these components is equipped with a pulley which is driven by the accessory drive belt. The accessory drive belt is driven by the engine crankshaft pulley. One or more idler pulleys may be provided to facilitate belt routing and alignment. The automatic belt tensioner maintains correct belt tension and compensates for component wear and changes in system load. System load changes can be caused by the A/C compressor clutch engaging or disengaging, or demand changes on other systems powered by the accessory drive belt. To maintain correct operation of this system, it is critical that the correct length drive belt be installed. The pulleys must also be correctly aligned and kept clean.

Scheme 624

Belt Tensioner

Automatic tensioners are calibrated to provide the correct amount of tension to the belt for a given accessory drive system. Unless a spring or damping band within the tensioner assembly breaks, or some other mechanical part fails, there is no need to check the tensioner for correct tension.

Scheme 625

Scheme 626

1. For additional information, see the procedures in this service information.

Scheme 627

1. With the vehicle in NEUTRAL, position it on a hoist. See «LIFTING»(ref-348626-S31954056142009112700000) .
2. Remove the pin-type retainer, 5 bolts and the RH lower splash shield. To install, tighten to 9 N.m {0.9 kgf.m, 80 in.lbf}.
3. Rotate the accessory drive belt tensioner counterclockwise and remove the accessory drive belt.
4. To install, reverse the removal procedure. NOTE: Refer to the illustration for correct belt routing.