Lubrication Flashcards
Oil functions
Reduce wear
Clean
absorb heat
seal
For long service life from engines
oil must be matched to the engine and the operating conditions
Viscosity
Viscosity is an oils resistance to flow
Measured by the time for a specific amount of oil to move through a fixed orifice at a certain temp
Oil with to high of viscosity will cause
increased load on the engine trying to overcome the friction of the oil
oil with to low of viscosity
oil will not cling together under load and causing metal to metal contact
SAE
society of automotive engineers
Viscosity index
the rate that oil will change viscosity as the temperature changes
pour point
is the lowest temperature at which the test fluid can be poured at a 45 degree angle
Oil additives
chemicals added to the oil by the manufacturer to eliminate specific problems that may be encountered during operation
carbon particles
is a by product of the combustion process and form an abrasive wear particle
detergents
keep oil by products from forming on internal engine parts
dispersants
keep deposits suspended in the oil to be collected in the filter
Oxidation inhibitors
prevent oil from absorbing excess oxygen also prevent general corrosion relating to alloy bearing material
Anti-rust agents
help maintain a film of oil on components when engine is not operating
API
American petroleum institute
sets standards for oil classification
SI classification
spark ignition engine oil
CI classification
Compression ignition Engine oil
Synthetic oil
Becoming more popular for its ability for cold weather starting and reduced drag on the engine
Storage and handling
oil and filter changes should have there own bay to avoid air born contamination
Majority of pre mature engine failure
Dirt introduced into the oil from service persons
Oil sampling
Analysis program that works best when developed by the appropriate oil laboratory and service tech
Most reliable oil sample is taken when
Oil is hot
sample location is clean
Taken from mid stream
Oil plugs with magnetic ends
Should be checked for after removal for contamination
two main purpose of oil analysis
determine the suitability of the oil
interpret results and determine if there are any existing internal problems
Oil analysis can reveal
proper oil temp during operation coolant leaks dirt and dust in engine fuel dilution effective oil filters crank case blow by effective oil change interval
Lubrication system functions
creates the pressure and provides the delivery system needed to move engine oil throughout the engine
Two types of lubrication systems
splash and pressurized
full pressure
Crankcase
used to store and cool supply of engine oil used in the system also allows dirt and debris to settle out
as well as air bubbles to disperse
RTV sealant
room temperature vulcanizing
can plug pick up screens if too much is used
Oil level indicators
Dip sticks and sight glass
oil must be check on level surface
Oil pressure gauge
reads the pressure of the oil during engine operation
will read high pressure when oil is cold
Engine run in
new engines have very small tolerance between components and oil pressure may read high until these components wear to a point where oil pressure will be a constant
Oil pump capacity
as much as 70% more to keep oil demand as engine wears over time
Two types of oil pumps
external gear
internal gear or rotor pump
external gear pumps
has two gears working in tandem to create a low pressure at the inlet and forcing oil out the outlet side
Rotor type pump
inner rotor drives the outer as rotor turns oil is squeezed between the rotor lobes and forced out the outlet
Pressure regulating valves
maintain system pressure during normal operating conditions
oil pressure relief valve
prevents system damage by allowing oil to return back to pan if pressures reach higher then operational normal
relief valve pressure set higher then regulating valve
Two types of oil coolers
Air to oil
oil to coolant
Oil bypass valve
thermostatic by pass valves allow cold oil to around bypass engine cooler until it reaches operating temp for faster warm up
two oil filter designs
bypass and full flow
by pass filter
5%-10% of oil from the oil pump is filtered and return directly back to oil pan
often clean oil much more thoroughly then full flow
may trap particles down to 10 microns in size
full flow filter
filters all oil supplied to the engine traps particles down to 25 to 60 microns in size
when bypass valve in filter is open
full flow filter becomes a shunt filter delivering both filtered and unfiltered oil to the engine
crank case ventilation system
required to remove water vapour oil vapour combustion vapours and fuel vapours
engine must remain warm to be most effective
crank case ventilation system operation
during vehicle a low pressure is formed at the end of outlet tube and vapours are drawn out and dispersed fresh air enters through the valve cover filter
