Ok, below is a detailed description of each system. As far as interconnectivity, there is none between the brakes and the oil lubrication and cooling systems. The only interconnectivity between the cooling system and engine oil lubrications system is the oil cooler. A hose from the cooling system goes the engine oil cooler and circulates coolant thru it as the oil goes thru it in separate passages. This is designed to keep the engine oil from overheating and breaking down its lubricating properties.
The cooling system is made up of the passages inside the engine block and heads, a water pump to circulate the coolant, a thermostat to control the temperature of the coolant, a radiator to cool the coolant, a radiator cap to control the pressure in the system, and some plumbing consisting of interconnecting hoses to transfer the coolant from the engine to radiator and also to the car's heater system where hot coolant is used to warm up the vehicle's interior on a cold day.
A cooling system works by sending a liquid coolant through passages in the engine block and heads. As the coolant flows through these passages, it picks up heat from the engine. The heated fluid then makes its way through a rubber hose to the radiator in the front of the car. As it flows through the thin tubes in the radiator, the hot liquid is cooled by the air stream entering the engine compartment from the grill in front of the car. Once the fluid is cooled, it returns to the engine to absorb more heat. The water pump has the job of keeping the fluid moving through this system of plumbing and hidden passages.
A thermostat is placed between the engine and the radiator to make sure that the coolant stays above a certain preset temperature. If the coolant temperature falls below this temperature, the thermostat blocks the coolant flow to the radiator, forcing the fluid instead through a bypass directly back to the engine. The coolant will continue to circulate like this until it reaches the design temperature, at which point, the thermostat will open a valve and allow the coolant back through the radiator.
In order to prevent the coolant from boiling, the cooling system is designed to be pressurized. Under pressure, the boiling point of the coolant is raised considerably. However, too much pressure will cause hoses and other parts to burst, so a system is needed to relieve pressure if it exceeds a certain point. The job of maintaining the pressure in the cooling system belongs to the radiator cap. The cap is designed to release pressure if it reaches the specified upper limit that the system was designed to handle. Prior to the '70s, the cap would release this extra pressure to the pavement. Since then, a system was added to capture any released fluid and store it temporarily in a reserve tank. This fluid would then return to the cooling system after the engine cooled down. This is what is called a closed cooling system.
The coolant follows a path that takes it from the water pump, through passages inside the engine block where it collects the heat produced by the cylinders. It then flows up to the cylinder head (or heads in a V type engine) where it collects more heat from the combustion chambers. It then flows out past the thermostat (if the thermostat is opened to allow the fluid to pass), through the upper radiator hose and into the radiator. The coolant flows through the thin flattened tubes that make up the core of the radiator and is cooled by the air flow through the radiator. From there, it flows out of the radiator, through the lower radiator hose and back to the water pump. By this time, the coolant is cooled off and ready to collect more heat from the engine
ABS Description and Operation
This vehicle is equipped with a Bosch ABS 9.0 brake system. The electronic brake control module and the brake pressure modulator valve are serviced separately. The brake pressure modulator valve uses a four circuit configuration to control hydraulic pressure to each wheel independently.
The following vehicle performance enhancement systems are provided.
* Brake Assist
* Electronic Brake Distribution
* Electronic stability control
* Hill start assist
* Traction control system
The following components are involved in the operation of the above systems:
* Electronic Brake Control Module - The electronic brake control module controls the system functions and detects failures. It supplies voltage to the solenoid valves and pump motor.
* Brake pressure modulator valve - The brake pressure modulator valve contains the hydraulic valves and pump motor that are controlled electrically by the electronic brake control module. The brake pressure modulator uses a four circuit configuration with a diagonal split. The brake pressure modulator directs fluid from the reservoir of the master cylinder to the left front and right rear wheels and fluid from the other reservoir to the right front and left rear wheels. The diagonal circuits are hydraulically isolated so that a leak or malfunction in one circuit will allow continued braking ability on the other.
The brake pressure modulator contains the following components:
- Brake pressure sensor
- Four inlet valves (one per wheel)
- Four outlet valves (one per wheel)
- Pump motor
- Two traction/stability control supply valves
- Two traction/stability control isolation valves
* Body control module monitors the brake pedal position sensor signal when the brake pedal is applied and sends a high speed serial data message to the electronic brake control module indicating the brake pedal position.
* Brake pressure sensor is used to sense the action of the driver application of the brake pedal. The sensor provides an voltage signal that will increase as the brake pedal is applied. The electronic brake control module monitors the brake pressure sensor which is integral to the brake pressure modulator.
* Instrument cluster - The instrument cluster displays the vehicle speed based on the information from the engine control module. The engine control module sends the vehicle speed information via a high speed serial data to the body control module. The body control module then sends the vehicle speed information via a low speed serial data to the instrument cluster in order to display the vehicle speed, either in kilometers or miles, based on the vehicle requirements.
* Multi-axis acceleration sensor - The yaw rate, lateral acceleration and longitudinal acceleration sensors are combined into one multi-axis acceleration sensor, internal to the inflatable restraint sensing and diagnostic module. The electronic brake control module receives serial data message inputs from the yaw rate, lateral acceleration and longitudinal acceleration sensor and activates stability control and hill hold start assist function depending on multi-axis acceleration sensor input.
* Multifunction switch - The traction control switch is a multifunction momentary switch. The body control module monitors the signal circuit from the traction control switch and sends a high speed serial data message to the electronic brake control module indicating the switch position. The traction control and stability control are manually disabled or enabled by pressing the traction control switch.
* Steering angle sensor - The electronic brake control module receives serial data message inputs from the steering angle sensor. The steering angle sensor is integrated in the power steering control module. The steering angle sensor signal is used to calculate the desired yaw rate.
* Transmission control module - The electronic brake control module receives high speed serial data message inputs from the transmission control module indicating the gear position of the transmission for hill start assist functions.
* Wheel speed sensors - The wheel speed sensors are Active sensors that receive a 12 V power supply voltage from the electronic brake control module and provides an output signal to the module. As the wheel spins, the wheel speed sensor sends the electronic brake control module a DC square wave signal. The electronic brake control module uses the frequency of the square wave signal to calculate the wheel speed.
The electronic brake control module is able to detect many malfunctions whenever the ignition is ON. However, certain failures cannot be detected unless active diagnostic tests are performed on the components. Shorted solenoid coil or motor windings, for example, cannot be detected until the components are commanded ON by the electronic brake control module. Therefore, a power-up self-test is performed to verify correct operation of system components. The electronic brake control module performs the first phase of the power-up self-test when the ignition is first turned ON. This phase consists of internal self-testing of the electronic brake control module along with electrical checks of system sensors and circuits.
The initialization sequence cycles each solenoid valve and the pump motor, as well as the necessary relays, for approximately forty milliseconds to check component operation. The active test is initiated by the electronic brake control module at the start of the ignition cycle and the speed of the fastest wheel exceeds 16 km/h (10 MPH). If a fault condition is detected the electronic brake control module sets a DTC.
When wheel slip is detected during a brake application, an ABS event occurs. During ABS braking, hydraulic pressure in the individual wheel circuits is controlled to prevent any wheel from slipping. A separate hydraulic line and specific solenoid valves are provided for each wheel. The ABS can decrease, hold, or increase hydraulic pressure to each wheel. The ABS does not, however, increase hydraulic pressure above the amount which is transmitted by the master cylinder during braking.
During ABS braking, a series of rapid pulsations is felt in the brake pedal. These pulsations are caused by the rapid changes in position of the individual solenoid valves as the electronic brake control module responds to wheel speed sensor inputs and attempts to prevent wheel slip. These pedal pulsations are present only during ABS braking and stop when normal braking is resumed or when the vehicle comes to a stop. A ticking or popping noise may also be heard as the solenoid valves cycle rapidly. During ABS braking on dry pavement, intermittent chirping noises may be heard as the tires approach slipping. These noises and pedal pulsations are considered normal during ABS operation.
Vehicles equipped with ABS may be stopped by applying normal force to the brake pedal. Brake pedal operation during normal braking is no different than that of previous non ABS systems. Maintaining a constant force on the brake pedal provides the shortest stopping distance while maintaining vehicle stability. The typical ABS activation sequence is as follows.
The electronic brake control module closes the inlet valve and keeps the outlet valve closed in order to isolate the system when wheel slip occurs. This holds the pressure steady on the brake so that the hydraulic pressure does not increase or decrease.
The electronic brake control module decreases the pressure to individual wheels during a deceleration when wheel slip occurs. The inlet valve is closed and the outlet valve is opened. The excess fluid is stored in the accumulator until the return pump can return the fluid to the master cylinder.
The electronic brake control module increases the pressure to individual wheels during a deceleration in order to reduce the speed of the wheel. The inlet valve is opened and the outlet valve is closed. The increased pressure is delivered from the master cylinder.
The brake assist function is designed to support the driver in emergency braking situations.
The electronic brake control module receives inputs from the brake pressure sensor. When the electronic brake control module senses an emergency braking situation, the electronic brake control module will actively increase the brake pressure to a specific maximum.
Electronic Brake Distribution
The electronic brake distribution function is designed to support the driver in emergency braking situations.
The electronic brake distribution is a control system that enhances the hydraulic proportioning function of the mechanical proportioning valve in the base brake system. The electronic brake distribution control system is part of the operation software in the electronic brake control module. The electronic brake distribution uses active control with existing ABS in order to regulate the vehicle's rear brake pressure.
Electronic Stability Control
The electronic stability control adds an additional level of vehicle control to the electronic brake control module.
Yaw rate is the rate of rotation about the vehicles vertical axis. The electronic stability control is activated when the electronic brake control module determines that the desired yaw rate does not match the actual yaw rate as measured by the yaw rate sensor.
The desired yaw rate is calculated from the following parameters:
* The speed of the vehicle
* The position of the steering wheel
* The lateral acceleration of the vehicle
The difference between the desired yaw rate and the actual yaw rate is the yaw rate error, which is a measurement of over steer or under steer. If the yaw error becomes too large, the electronic brake control module attempts to correct the vehicles yaw rate motion by applying differential braking to the appropriate wheel. The amount of differential braking applied to the left or right front wheel is based on both the yaw rate error and side slip rate error.
The electronic stability control activations generally occur during aggressive driving, in turns or on bumpy roads without much use of the accelerator pedal. When braking during electronic stability control activation, the pedal pulsations feel different than the ABS pedal pulsations. The brake pedal pulsates at a higher frequency during vehicle stability enhancement system activation.
Hill Start Assist
When stopped on a hill, the hill start assist feature prevents the vehicle from rolling before driving off, whether facing uphill or downhill by holding the brake pressure during the transition between when the driver releases the brake pedal and starts to accelerate. The electronic brake control module calculates the brake pressure, which is needed to hold the vehicle on an incline or grade greater than 5% and locks that pressure for up to two seconds by commanding the appropriate solenoid valves ON and OFF when the brake pedal is released. The stop lamps will stay illuminated during the hill start assist operation even though the brake pedal is released, this is considered normal operation.
The hill start assist feature is determined by the electronic brake control module using the following inputs:
* Accelerator pedal position
* Brake pedal position sensor
* Brake pressure
* Clutch switch, if equipped
* Engine torque
* Longitudinal acceleration
* Multi-axis acceleration sensor
* Transmission gear information
* Vehicle speed
Traction Control System
When drive wheel slip is noted while the brake is not applied, the electronic brake control module will enter traction control mode.
First, the electronic brake control module requests the engine control module to reduce the amount of torque to the drive wheels via the serial data. The engine control module reduces torque to the drive wheels by retarding spark timing and turning off fuel injectors. The engine control module reports the amount of torque delivered to the drive wheels via the serial data circuit.
* Pressure hold
* Pressure increase
* Pressure decrease
Lubrication Description (Engine Oil)
1 - Engine Oil Tank
2 - Oil Fill Cap
3 - Oil Level Indicator
4 - Oil Pressure Sensor
5 - Valve Lifter Oil Filter
6 - AFM Solenoid
7 - Upper Main Oil Galleries
8 - AFM Valve Lifters
9 - Valve Lifters
10 - Piston Oil Nozzle
11 - Camshaft Bearings
12 - Crankshaft Bearings
13 - Bypass Valve - Oil Cooler
14 - Engine Oil Cooler
15 - Oil Filter
16 - Oil Pan Sump
17 - Oil Pump Screen
18 - Pressure Relief Valve - Oil Pump
19 - Oil Pump - Primary
20 - Oil Pump - 1st Stage Pressure Cavity
21 - Oil Cooler
22 - Oil Pump - Secondary
23 - CMP Actuator
24 - Oil Tank Screen
25 - Oil Temperature Sensor
Engine lubrication is supplied by a two-stage oil pump assembly. The oil pump assembly consists of a primary vane-type variable displacement pump and a secondary geroter-style pump. The primary pump contains a pressure relief valve that protects the oil pan mounted oil filter from over pressurization during cold engine start up. If system pressure exceeds 600 kPa (87 psi), the pressure relief valve will open and exhaust oil back into the oil pan. The front or forward gear set is the secondary pump (22). The rear or rearward housing contains the primary pump (19). Refer to Oil Pump Assembly in Disassembled Views (6.2L LT1) See: Engine > Components > Disassembled Views (6.2L LT1)Disassembled Views (6.2L LT1 with Z52 Option) See: Engine > Components > Disassembled Views (6.2L LT1 with Z52 Option). The pump assembly is mounted at the front of the engine and driven directly by the crankshaft sprocket. The vanes of the primary pump (19) rotate clockwise and draw oil from the engine oil tank (1) through the oil tank screen (24). The oil is pressurized as it passes through the primary pump and is sent through the engine block lower oil gallery.
Pressurized oil is directed through the engine block lower oil gallery to the full flow oil filter (15) where harmful contaminants are removed. A bypass valve is incorporated into the oil filter, which permits oil flow in the event the filter becomes restricted.
Oil exits the oil filter and is then directed to the external oil cooler (14). The external oil cooler consists of an oil pan mounted core, coolant lines and a reservoir in the vehicle radiator. A bypass valve (13) is incorporated into the oil cooler assembly in the event oil flow within the cooler is restricted. Oil returns from the oil cooler and is directed to the upper main oil galleries (7) and Valve Lifter Oil Manifold Assembly.
Oil from the left upper oil gallery is directed to the crankshaft bearings (12), valve lifter bores for cylinders 1, 3, 5, and 7, camshaft bearings (11), and piston oil nozzles (10) for cylinders 1, 3, 5, and 7. Oil from the right upper oil gallery is directed to the valve lifters bores for cylinders 2, 4, 6, and 8 and piston oil nozzles (10) for cylinders 2, 4, 6, and 8. The piston oil nozzle assemblies are designed to provide oil to the bottom side of the piston for cooling purposes. The piston oil nozzles have an internal check ball that is held in the normally closed position by the spring until system oil pressure exceeds 300 kPa (43.5 psi).
An oil passage at camshaft bearing location 1 permits oil flow to the upper rear of the primary oil pump (19). Oil is pumped through this passage and provides hydraulic pressure to the first stage oil pressure cavity (20) in the primary oil pump (19). Hydraulic pressure in the first stage pressure cavity regulates engine oil pressure and can help reduce the load on the engine during normal operating conditions.
An oil passage at camshaft bearing location 2 permits oil flow into the center of the camshaft. Oil enters the camshaft exiting at the front and into the camshaft position (CMP) actuator solenoid valve (23). The CMP valve spool position is controlled by the engine control module (ECM) and CMP magnet. When commanded by the ECM, the CMP magnet repositions the CMP actuator solenoid valve spool directing pressurized oil into the CMP actuator to control valve timing.
Oil from the right upper gallery is also pumped up to the Valve Lifter Oil Manifold Assembly. A Valve Lifter Oil Filter (5) and Oil Pressure Sensor (4) are located on the right front side of the Valve Lifter Oil Manifold Assembly. With active fuel management activated, or ON, the ECM commands the 4 manifold solenoids (6) to open, directing oil through the manifold and to the 4 active fuel management intake and exhaust valve lifters (8), for cylinders 1, 4, 6, and 7.
Oil exits the valve lifters and is then pumped through the pushrods to lubricate the valve rocker arms and valve stems. Oil returns to the oil pan (16), where the secondary pump (22) draws oil through a oil pump screen (17). The secondary pump (22) returns oil to the engine oil tank (1). Incorporated within the engine oil tank assembly are the oil level indicator (3), oil fill cap (2), oil temperature sensor (25), positive crankcase ventilation (PCV) fresh air port, and an oil pump screen (24).
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