Engine Description

Crankcase Ventilation System Description





The compressed combustion gas, which escapes past the piston rings into the crankcase is known as blowby gas. Blowby gas contains large amounts of carbon monoxide (CO) and hydrocarbon (HC). The positive crankcase ventilation (PCV) system prevents the blowby gas from being emitted into the atmosphere. The PCV system routes crankcase blowby gas back into the intake system where it becomes part of the combustion process. The PCV system consists of the following components:
- The PCV valve
- The crankcase vent or air inlet tube
- The air inlet filter or separator, if used
- Any hoses or couplers

Operation
The primary control of engine crankcase blowby gas is the PCV valve. The PCV valve meters the flow of blowby gas according to the manifold vacuum signal.

PCV Valve





In order to maintain idle quality, the PCV valve restricts the flow of blowby gas whenever intake manifold vacuum is high. Abnormally high crankcase pressure may cause the blowby gases to flow through the crankcase vent tube and into the air cleaner. The blowby gases are then drawn into the intake system and consumed in the normal combustion process. The relationship between the flow of blowby gas and engine manifold vacuum is charted in the following table:





PCV Valve Operation

Results Of Incorrect Operation
A plugged valve or hose may cause any of the following conditions:
- A rough engine idle
- Engine stalling or low engine idle speed
- High engine crankcase pressure
- Engine oil leaks
- Engine oil in the air cleaner
- Oil sludge in the engine
- Engine oil consumption
- Excessive exhaust emissions
A leaking valve or hose may cause any of the following conditions:
- A rough engine idle
- Engine stalling
- High engine idle speed
- Incorrect engine crankcase pressure
- Excessive exhaust emissions

Drive Belt System Description
The drive belt system consists of the following components:
- The drive belt
- The drive belt tensioner
- The drive belt idler pulley
- The crankshaft balancer pulley
- The accessory drive component mounting brackets
- The accessory drive components
- The power steering pump, if belt driven
- The generator
- The A/C compressor, if equipped
- The engine cooling fan, if belt driven
- The water pump, if belt driven
- The vacuum pump, if equipped
- The air compressor, if equipped
The drive belt system may use 1 belt or 2 belts. The drive belt is thin so that it can bend backwards and has several ribs to match the grooves in the pulleys. There also may be a V-belt style belt used to drive certain accessory drive components. The drive belts are made of different types of rubbers- chloroprene or EPDM-and have different layers or plys containing either fiber cloth or cords for reinforcement.
Both sides of the drive belt may be used to drive the different accessory drive components. When the back side of the drive belt is used to drive a pulley, the pulley is smooth.
The drive belt is pulled by the crankshaft balancer pulley across the accessory drive component pulleys. The spring loaded drive belt tensioner keeps constant tension on the drive belt to prevent the drive belt from slipping. The drive belt tensioner arm will move when loads are applied to the drive belt by the accessory drive components and the crankshaft.
The drive belt system may have an idler pulley, which is used to add wrap to the adjacent pulleys. Some systems use an idler pulley in place of an accessory drive component when the vehicle is not equipped with the accessory.

Tools and Equipment
Special tools (or their equivalents) are specially designed to quickly, and safely accomplish the operations for which they are intended. The use of these special tools will also minimize possible damage to engine components. Some precision measuring tools are required for inspection of certain critical components. Torque wrenches and a torque angle meter are necessary for the proper tightening of various fasteners.
To properly service the engine assembly, the following items should be readily available:
- Approved eye protection and safety gloves
- A clean, well-lit, work area
- A suitable parts cleaning tank
- A compressed air supply
- Trays or storage containers to keep parts and fasteners organized
- An adequate set of hand tools
- Approved engine repair stand
- An approved engine lifting device that will adequately support the weight of the components