DICTIONARY OF AUTOMOTIVE TERMS - "Me"

Mean:

See indicated mean effective pressure

Mean distance to the sun:

240 million miles; used to specify the headroom in convertibles

Mean effective pressure: (MEP)

The average pressure of the burning fuel on the power stroke subtracted by the average pressure on the other three strokes. Pressure is in pounds per square inch.

Average pressure on a surface when a changing pressure condition exists.
Also See:
brake mean effective pressure
indicated mean effective pressure

Mean indicated pressure:

A mathematical value that indicates the relation between the effective area of the work diagram of the two-stroke engine and the movement of the piston

Measuring:

See:
ionic-current measuring technique
pushrod measuring tool

Measuring method:

See ionic-current measuring method

Measuring technique:

See ionic-current measuring technique

Measuring tool:

See pushrod measuring tool

Mechanic:

A person who works on engines or machines.
Also See:
automobile mechanic
car mechanic
DIY mechanic
do-it-yourself mechanic
motor mechanic

Mechanical advance:

See centrifugal advance mechanism

Mechanical advantage:

The ratio of the force exerted to the force applied. A manual brake pedal may have a mechanical advantage, or pedal ratio of 5 to 1.

Mechanical brake:

See mechanical brakes.

Mechanical brakes:

Service brakes that are actuated by a mechanical linkage such as rods or cables (rather than hydraulic lines) connecting the brakes to the brake pedal. The parking brake on most vehicles is mechanical.

Mechanical cycle:

Cycle which is a repetitive series of mechanical events.

Mechanical degree:

The popular physical understanding of degrees (360°=1 rotation)

Mechanical efficiency:

An engine's rating as to how much of the potentialhorsepower is wasted through friction within the moving parts of the engine. The ratio between the indicated horsepower and the brake horsepower of an engine.

Mechanical face seal:

A shaft seal consisting of two highly polished mating surfaces, one surface being connected to the shaft (rotating element) and the other to the casing (stationary element)

Mechanical fade:

Brake fade caused by heat expansion of the brake drum away from the brake linings. Not a problem with disc brakes.

Mechanical galvanizing:

See mechanical plating

Mechanical-hydraulic booster:

A power booster that uses hydraulic pressure from the power steering pump to increase brake application force.

Mechanical ignition timing:

Centrifugal and vacuum advance

Mechanical plating:

A deposition of zinc on another material by a cold-peening process, such as tumbling

Mechanical protection:

Where clogging materials are present in severe proportions, the air gap of open enclosure electric motors may become clogged. Therefore, the recommendation is a totally enclosed motor housing to obtain mechanical protection from the elements.

Mechanical seal:

A shaft seal consisting of two highly polished mating surfaces, one surface being connected to the shaft (rotating element) and the other to the casing (stationary element)

Mechanical stress:

A force acting across a unit area in solid materials in resisting the separation, compacting, or sliding that tends to be induced by external forces

Mechanical surface treatment:

A production of a dull or rough surface or a decorative finish by grinding, brushing, polishing, or abrasive blasting

Mechanic installed market:

(MIL) Vehicle maintenance and repair conducted by a mechanic/professional at a service outlet.

Mechanic's creeper:

See creeper

Mechanic's elbow:

A shallow dent in body panels, usually on the top of a fender near the engine compartment; caused when leaning over into the engine compartment and supporting the body with elbows on the fender

Mechanics lien:

When you take your vehicle to a shop to be repaired and you fail to pay your repair bill, the repair shop has a lien on your vehicle and can confiscate and sell your vehicle to pay for the work on your vehicle.

Mechanic's stethoscope:

See sonoscope

Mechanism:

See:
gearchange mechanism
locking mechanism
shifter mechanism
vacuum advance mechanism

MECP:

Acronym for "Mobile Electronics Certification Program."

Median:

See center median

Medium:

See aggressive medium

Medium carbon:

A type of carbon steel used extensively for sheet metal screws and grade 2 hex head bright cap screws.

Medium-duty truck:

Vehicle weighing from 10,001 to 25,000 lbs.

Megajoule:

(MJ) An SI measurement of energy (= l000 joules)

Megger:

A portable instrument used to measure insulation resistance. It consists of a hand-driven DC generator and a direct reading ohm meter.

Megohm:

A unit of measure for electrical resistance. One megohm is equal to a million ohms.

Megohmmeter:

Instrument for measuring extremely high resistances (in the millions of ohms ranges).

Melting point:

Temperature at atmospheric pressure at which a substance will melt.

MEMA:

Acronym for "Motor and Equipment Manufacturers Association."

Member:

A general term that refers mainly to the side rails and crossmembers but also to any structural hollow-section part on a vehicle.
Also See:
box member
cross member
frame member
longitudinal member
main member
reaction member
side member

Member of the gear train:

Sun gear, internal gear, and planet carrier are the members of a planetary gear train

Membrane:

See sill membrane

Memory:

See:
alive memory
fault memory
keep alive memory
last station memory

Memory button:

A button which operates the position of electric seats, mirrors, etc. and which stores the requirements of a particular driver in its memory

MEP:

Acronym for "mean effective pressure."

MERA:

Acronym for "Mobile Electronics Retailers Association."

Mercedes:

A vehicle brand of which the 1925-1948 models with required application are classic cars.
Click for books on Mercedes

Mercedes-Benz:

A vehicle brand of which all 230 and up, and K, S, SS, SSK, SSKL, Grosser and Mannheim models with required application are classic cars. The 1955-61 190 SL models are milestone cars. The 1951-54 220A Coupe and Convertible are milestone cars. The 1956-65 220S/220SE Coupe and Convertible are milestone car. The 1963-67 230SL Coupe and Convertible are milestone cars. The 1965-67 250SE Coupe and Convertible are milestone cars. The 1965-67 250 SL models are milestone cars. The 1969-70 280 SL models are milestone cars. The 1965-67 300 SE Coupe and Convertible are milestone cars. The 1952-64 300 S, SL, SE, 300 Coupe and Convertible are milestone cars. The 1964 600 model is a milestone car. The 1965-70 SWB-LWB 600 models are milestone cars.
Click image for books on Mercedes-Benz

Mercer:

A vehicle brand of which the 1925-1948 models are classic cars.

Mercoid bulb:

Electrical circuit switch which uses a small quantity of mercury in a sealed glass tube to make or break electrical contact with terminals within the tube.

Mercosur:

The southern zone common market of Argentina, Brazil, Paraguay, and Uruguay. Mercosur enacted a common external tariff on January 1, 1995 for almost 85 percent of tariff items of the four countries; most trade among members will be duty-free.

Mercury:

A vehicle brand of which the 1967-68 Cougar XR-7 models are milestone cars. The 1946 Sportsman is a milestone car. The 1954-55 Sun Valley models are milestone cars.
Click image for books on Mercury

Mercury column:

A reference term used in connection with a manometer

Mercury switch:

Safety switch to prevent erroneous deployment of the air bag. Due to ecological problems associated with mercury in automobile waste, mercury switches are being replaced by suspended-mass switches, e.g., a Hamlin switch

Merkur:

A model of automobile manufactured by Ford of Europe
Click image for books on Merkur

Mesh:

To engage, especially gears. The opposite is disengage.
Also See:
constant-mesh gearbox
metal mesh
stainless-steel mesh
wire mesh

Mesh gearbox:

See:
constant mesh gearbox
constant mesh gears

Meshing drive:

A device for engaging the starter pinion with the flywheel ring gear

Meshing spring:

A component of a pre-engaged starter which ensures that the shift lever will move to its final position and that the starter current will be switched on in case of tooth abutment

Message center:

Usually a multifunctional display of a diagnostic system. A typical messages are: "NORMAL," "DOOR AJAR," "TAILGATE OPEN," "LAMP OUT," "WASHER FLUID LOW," etc.

Met:

Term applied to the heat release from a human at rest. It equals 1 8.4 Btu/sq. ft./hr. (50 kcal/m2/hr or 58 W/m2).

Metacenter:

The intersection point of a vertical line drawn through the line of buoyancy of a slightly listed vessel which intersects the centerline plane

Metacentric height:

The distance from the metacenter to the center of gravity of a ship. If the center of gravity is below the metacenter the vessel is stable

Metal:

See:
babbitt metal
base metal
burned metal
ferrous metal
heavy sheet metal
light sheet metal
noble metal
nonferrous metal
pedal to the metal
platinum metals
pot metal
scrap metal
sheet metal
sound metal
weld metal
white metal

Metal-arc:

See gas metal-arc welding

Metal-arc welding:

See gas metal-arc welding

Metal blank:

See sheet metal blank

Metal brake pad:

See sintered metal brake pad

Metal catalyst:

A catalyst whose active phase is supported by a metal substrate, i.e., sheet steel. Compare metal monolith

Metal clamp:

See sheet metal clamp

Metal conditioner:

An acid-based metal cleaner that removes rust and corrosion from bare metal, etches it for better adhesion and forms a corrosion resistant film

Metal cutter:

A bench tool for cutting sheet metal.
Also See:
sheet metal cutter

Metal fatigue:

A crystallizing of the metal due to vibration, twisting, bending, etc. The unit will eventually break. Bending a piece of wire back and forth to break it is a good example of metal fatigue. See fatigue.

Metal folder:

See sheet metal folder

Metal forming:

Solid metal and molten metal process such as casting, forging, stamping, and machining.

Metal inert gas welding:

See MIG welding

Metallic:

Referring to or consisting of metal

Metallic drive screw:

A British term for a self-tapping screw

Metallic finish:

A type of paint in which tiny flecks of shiny metal has been added in order to give a sparkle effect.

Metallilc friction material:

A sintered friction material formulated with metallic or metallic-ceramic materials.

Metallic paint:

A finish paint colors that contain both pigment and small metallic flakes which reflect light. The opposite is solid paint. The flakes are often of different sizes. When the surface is viewed from different angles, the color shade seems to vary, since the flakes are all oriented at different angles in the paint and consequently reflect the light differently. Japanese motorcycles used a different size of flakes than was common in the USA. As a result, repainted tanks in the USA did not have the same "look."

Metallize:

To coat or impregnate a metal or non-metal surface with metal, as by metal spraying or by vacuum evaporation

Metallographic examination:

A test to determine the structural composition of a metal as shown at low and high magnification and by X-ray diffraction methods. Tests of this type include macro-examination, micro-examination, and X-ray diffraction analysis

Metal mesh:

See wire mesh

Metal monolith:

See metal support

Metal remains:

See sheet metal remains

Metal roller:

See sheet metal roller

Metal shafts:

These are used to attach the connecting rods to the crankshaft (also called eccentric journals)

Metal shears:

A scissor-like hand tool for cutting sheet metal. Also called "snips"

Metal spraying:

A coating of surfaces with droplets of molten metal or alloy by using a compressed gas stream

Metal support:

A thin corrugated strips of steel alloy rolled up into a tight coil as a support for the catalyst in a catalytic converter.
Also See:
ceramic honeycomb

Metalworking:

Forming and shaping metal

Metalworking spoon:

See body spoon

METC:

Acronym for "Mobile Electronics Technical Center."

Meter:

1. A device for measuring the quantity of a substance passing through it.
2. To measure with a meter.
3. To supply at a measured rate.
4. A distance of about a yard (actually a little over 39.37"). Also spelled "metre."

Also See:
airflow meter
CO meter
dwell meter
hot-wire airflow meter
L-jetronic air flow meter
mass airflow meter
newton meter
parking meter
smoke meter
trip meter

Metering jet:

A small hole or orifice used to control the flow of gasoline in various parts of the carburetor.

Metering orifice:

A small hole that restricts the flow of liquid -- usually coolant or oil

Metering port:

A part of the metering unit in the fuel distributor

Metering rod:

A thin, movable rod which varies the opening area in a carburetor jet. As the rod is raised it permits more fuel to enter the jet.

Metering signal:

A (relative) vacuum signal generated by the pressure differential that occurs at the venturi. The strength of the metering signal determines how much fuel is pulled from the main circuit into the venturi. The smaller the venturi the greater the pressure drop and the stronger the metering signal; the larger the venturi, the smaller the pressure drop and the weaker the metering signal

Metering slits:

In Bosch CIS, the narrow slits in the control-plunger barrel of the fuel distributor. Fuel flows through the slits in accordance with the lift of the control plunger and the pressure drop at the slits

Metering unit:

A unit which regulates the quantity of fuel injected in the K-jetronic system. A lever connected to the sensor plate raises or lowers a stepped control plunger in the metering unit. The position of the control plunger relative to the metering ports in the metering unit varies the flow of fuel to the fuel injectors

Metering valve:

1. A valve positioned in the hydraulic line to the front brakes, on some cars with front disc and rear drum brakes. It prevents the disc brakes from applying until after the rear brake linings contact the drum. The metering valve closes off pressure to the front disc brakes until a specified pressure level is generated in the master cylinder. This allows pressure in the rear brake circuit to overcome return spring force and an gap before the hydraulic pressure is admitted to the front disc brakes
2. A hydraulic control valve placed in the circuit to the front brakes, designed to restrict pressure to the front brake calipers until the rear brake shoes overcome the tension of the retracting spring
3. A hydraulic valve used in some brake systems to slightly delay the application of front-disc brakes to obtain a balanced braking.

Methacrylate:

A polymer used in toughening rubber.
Also See:
polymethyl methacrylate

Methanol:

An alcohol that is occasionally blended with gasoline (typically 3%) to raise octane levels, it is poisonous to humans and causes trouble with rubber and plastic parts of the fuel system not designed to handle alcohol-blended fuels. Also called "methyl alcohol" or "wood alcohol."

Methyl alcohol:

See methanol.

Methylated spirits:

Almost pure alcohol (which has wood alcohol and coloring added to make it unfit for human consumption); used for cleaning

Methylcyclopentadienyl Manganese Tricarbonyl:

(MMT) An organic manganese compound. It is used as a fuel additive designed to enhance octane levels in gasoline.

Metre:

See meter

Metric century:

A bicycle ride of 100 kilometers (62.14 miles). See century.

Metric size:

Units made to metric system measurements.

Metric system:

Decimal system of measuring.

Metric thread:

The threads of metric nuts, bolts, and screws. Two primary styles were common: ISO (International Standardization Organization) and JIS (Japanese Industrial Standard) which is no longer used. UNC thread and UNF thread cannot be interchanged with any metric nut or bolt.

Nominal diameter	Width across flat		Pitch
	ISO	JIS	ISO	JIS
3	5.5	6	0.5	0.6
4	7	8	0.7	0.75
5	8	9	0.8	0.9
6	10	10	1.0	1.00
8	12	14	1.25	1.25
10	14	17	1.25	1.25
12	17	19	1.25	1.5
14	19	21	1.5	1.5
16	22	23	1.5	1.5
18	24	26	1.5	1.5
20	27	29	1.5	1.5

Metro driving:

An American term for driving exclusively in the city rather than on the highway. The British term is "urban driving."

MEWA:

Acronym for "Motor and Equipment Wholesalers Association."

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