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Txn fluid

A transmission is a complex piece of machinery, and many different factors can cause it to wear

down sooner than it should. Whatever the underlying cause, most transmissions start wearing out

due to heat taking its toll on the individual parts. The most effective thing you can do to limit the

heat on a transmission is to keep it lubricated. A common mistake is to believe that any old

transmission fluid will do. Specific transmissions are built to perform optimally under particular

conditions, using transmission fluid that works best for them. So while there are more than 50

different fluids available, use only the one that is best for your transmission. You should also have

the fluid changed at regular intervals to maximize transmission longevity. Your car manufacturer's

maintenance schedule will tell you how often the transmission fluid should be changed. Be sure to

factor in how often and how hard you drive your car. Experts define severe use on a car as driving it

more than 50 percent of the time in heavy city traffic, with temperatures above 90 degrees F (32.2

degrees C). If this sounds like you, the recommended interval for changing the transmission fluid is

every 15,000 miles (24,140 kilometers).

If your transmission is due for a fluid change, it's probably not a smart move to try it yourself; it's

not as simple as changing the oil. An experienced service technician will inspect used fluid for

contaminants and other indications of any impending mechanical problems. Regardless of whochanges your transmission fluid, you should know how to check it from time to time. If you have an

automatic transmission, it likely came with a special dipstick, one that's different from your oil

dipstick. Keep the car running (your manual will tell you whether the car should be in neutral or

park) and smell the fluid when you remove the dipstick from the transmission. If it there is a burnt

smell, it could indicate a problem. Now wipe the fluid on a white paper or cloth and compare it to a

sample of fresh fluid. If there is a great variation in color, that could also indicate a problem

Provides Hydraulic Power

The main function of transmission fluid is to provide the hydraulic (fluid) power

used by an automatic transmission to perform its basic functions. All automatic

transmission functions--gear changing, transmission engagement and disengagement,

and downshifting--require the force provided by transmission fluid. Unlike manual

transmissions, which use manually operated clutches, gear shifts, and linkages, an

automatic transmission uses transmission fluid to operate those transmission

components. Pressurized transmission fluid provides the physical force, or pressure,

to perform automatic transmission functions.

Lubricates and Cools

As transmission fluid flows throughout an automatic transmission, it lubricates the

transmission gears and bands and helps to keep transmission operating temperatures

reduced. Just like an engine uses motor oil to lubricate and cool its inner parts, a

transmission uses automatic transmission fluid to perform the same functions. Heat

and friction are natural by-products of automatic transmission gear and band

function; transmission fluid reduces heat and friction and ultimately increases

automatic transmission life.

Collects in Transmission Pan

When a vehicle is not running and its automatic transmission is not in use, all thetransmission fluid flows into the transmission pan, a square metal holding basin

located directly underneath the car. The transmission pan is similar to a vehicle's oil

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pan. Both pans serve as nothing more than catch basins and reservoirs. When

transmission fluid is added to a vehicle, the fluid is poured directly into the

transmission dipstick, which funnels the fluid directly into the transmission pan.

When a vehicle is started, the automatic transmission engages and all the stored

automatic transmission fluid stored in the transmission pan begins to circulate

throughout the entire transmission.

Brake fluid

Brake fluid is a type of hydraulic fluid used in hydraulic brake and hydraulic clutch

applications in automobiles, motorcycles, light trucks, and some bicycles. It is used to transfer

force into pressure. It works because liquids are not appreciably compressible - in their

natural state the component molecules do not have internal voids and the molecules pack

together well, so bulk forces are directly transferred to trying to compress the fluid's chemical

bonds.

Because oils damage rubber seals and hoses in the braking system, brake fluids are not petroleum-

based. Most brake fluids used today are glycol-ether based, but mineral oil (Citron liquide

hydraulique minral (LHM) and silicone (DOT 5) based fluids are also available. Brake fluids must

meet certain requirements as defined by various standards set by organizations such as the SAE, or

local government equivalents. For example, most brake fluid sold in North America is classified by

the US Department of Transportation (DOT) under their own ratings such as "DOT 3" and "DOT

4". Their classifications broadly reflect the concerns addressed by the SAE's specifications, but with

local details - Alaska and theAzores have different normal temperature and humidity ranges to

consider, for example. Many countries defer explicitly to the SAE specifications, or simply refer to

"best practice" which in practice would defer to the SAE.

Characteristics

Brake fluids must have certain characteristics and meet certain quality standards for the braking

system to work properly.

Boiling point

Brake fluid is subjected to very high temperatures, especially in the wheel cylinders of drum brakes

and disk brake calipers. It must have a high boiling point to avoid vaporizing in the lines. This

vaporization is a problem because vapor is compressible and negates hydraulic fluid transfer of

braking force.Quality standards refer to a brake fluid's "dry" and "wet" boiling points. Wet boiling point, which is

usually much lower (although above most normal service temperatures), refers to the fluid's boiling

point after absorbing a certain amount of moisture. This is several (single digit) percent, varying

from formulation to formulation. Glycol-ether (DOT 3, 4, and 5.1) brake fluids are hygroscopic

(water absorbing), which means they absorb moisture from the atmosphere under normal humidity

levels. Non-hygroscopic fluids (e.g. silicone/DOT 5-based formulations), are hydrophobic, and can

maintain an acceptable boiling point over the fluid's service life, although at the cost of potential

phase separation/water pooling and freezing/boiling in the system over time - the main reason single

phase hygroscopic fluids are used.

Boiling points for common braking fluids ,Wet boiling point defined as 3.7% water by volume.

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Viscosity

For reliable, consistent brake system operation, brake fluid must maintain a constant viscosity under

a wide range of temperatures, including extreme cold. This is especially important in systems with

an anti-lock braking system (ABS), traction control, and stability control (ESP).

Corrosion

Brake fluids must not corrode the metals used inside components such as calipers, master cylinders,

etc. They must also protect against corrosion as moisture enters the system. Additives (corrosion

inhibitors) are added to the base fluid to accomplish this.

The advantage of the Citron LHM mineral oil based brake fluid is the absence of corrosion. Seals

may wear out at high mileages but otherwise these system have exceptional longevity. It cannot be

used as a substitute without changing seals due to incompatibility.[citation needed]

Compressibility

Brake fluids must maintain a low level of compressibility that remains low, even with varying

temperatures.

Service and maintenance

Most automotive professionals agree that glycol-based brake fluid, (DOT 3, DOT 4, DOT 5.1)

should be flushed, or changed, every 12 years.[1] Many manufacturers also require periodic fluid

changes to ensure reliability and safety. Once installed, moisture diffuses into the fluid through

brake hoses and rubber seals and, eventually, the fluid will have to be replaced when the water

content becomes too high. Electronic testers and test strips are commercially available to measure

moisture content, however moisture test strips were taken off the market because they absorb

moisture in the air before they can be used. The corrosion inhibitors also degrade over time.

Degraded inhibitors cause corrosion in the braking system. The first metal to corrode is copper. Youcan determine when it is time to replace brake fluid when copper ions hit 200ppm.[2] New fluid

should always be stored in a sealed container to avoid moisture intrusion.

DOT 5 is silicone fluid and the above does not apply. Ideally, silicone fluid should be used only to

fill non-ABS systems that have not been previously filled with glycol based fluid. Any system that

has used glycol based fluid will contain moisture; glycol fluid disperses the moisture throughout the

system and contains corrosion inhibitors. Silicone fluid does not allow moisture to enter the system,

but does not disperse any that is already there, either. A system filled from dry with silicone fluid

does not require the fluid to be changed at intervals, only when the system has been disturbed for a

component repair or renewal. The United States armed forces have standardised on silicone brake

fluid since the 1990s. Silicone fluid is used extensively in cold climate, particularly in Russia andFinland.

A small drop in brake fluid level in the master cylinder reservoir can be "topped up" but if the level

consistently drops, the cause should be investigated and repaired. Brake fluid level in the master

cylinder will drop as the linings (pads or shoes) wear and the calipers or wheel cylinders extend

further to compensate. Overspill from pushing back pistons should be avoided, because glycol

based fluid will quickly lift or strip paints and other coatings on contact (it can be removed by

quickly washing with water, not wiping). Brake fluid level may also be low because of a leak,

which could result in a loss of hydraulic pressure and consequently a significant loss of braking

ability. Modern cars have split hydraulic circuits to ensure against total hydraulic failure. Brake

fluids with different DOT ratings should not be mixed; not all DOT fluid is compatible. This is

because it will dilute and reduce the properties of the higher specification DOT fluid, or in the case

of mixing of glycol with silicone fluid may cause corrosion due to trapped moisture.

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Oil pressure

Oil pressure is an important factor in the longevity of most internal combustion engines. With

a forced lubrication system (invented by Frederick Lanchester), oil is picked up by a positive

displacement oil pump and forced through oil galleries (passageways) into bearings, such as

the main bearings, big ends and camshaft bearings. Other components such as cam lobes and

cylinder walls are lubricated by oil jets.

Sufficient oil pressure ensures that the metal of the rotating shaft (journal) and the bearing shell can

never touch, and wear is therefore confined to initial start-up and shutdown. The oil pressure,

combined with the rotation of the shaft, also hydrodynamically centers the journal in its shell and

cools the bearings. Such a bearing is known as a fluid bearing.

Oil pressure is higher when the engine is cold due to the increased viscosity of the oil, and also

increases with engine speed until the relief valve opens to divert excess flow. Oil pressure is lowest

under hot idling conditions, and the minimum pressure allowed by the manufacturer's tolerances is

usually given at this point. Excessive oil pressure may indicate a blocked filter, blocked oil gallery

or the wrong grade of oil. Low oil pressure indicates worn bearings on the crank shaft or a broken

oil pump.Engine Oil Pressure

A worn oil pump will cause low oil pressure. They wear in time and the clearance between the

pump housing and the gears, shaft end play, etc. gets excessive resulting in a loss of oil pressure.

Pumps also fail if debris in the oil gets caught in the housing causing premature wear and damage.

If the pickup screen gets clogged this will cause a restriction to oil flow and a loss in oil pressure.

Bearings are designed to wear and are replaced whenrebuilding an engine. The growing gap between the bearing and the journal increases the flow

which in turn lowers the oil pressure. These two are proportionate to each other, the more flow

between the bearing and the journal the lower the oil pressure.

Worn crankshaft, camshaft, and rod bearings will all cause a loss in oil pressure. There are different

specifications and tolerances according to the application. Most manufacturers and machinists will

tell you no more than .001 inch off the diameter of the bearing. Bearings should also be checked for

scoring and tapered wear. This may indicate a problem with a worn or damaged part such as a

twisted rod.

High oil pressure may be present. A restriction in the oil filter, a stuck closed or clogged oil pressure

valve will cause high oil pressure. This can be a bad thing. High oil pressure can result in oilleaking past the oil seals and oil leaks in other areas of the engine. Either way, always keep your eye

on the engine oil light or gauge during a test drive and inform your customers of its location,

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importance, and function.

fuel pressure

A fuel pressure regulator (FPR) is a device which is designed to keep the pressure in the fuel

lines of a vehicle consistent. It is located between the fuel source and the engine, along the fuel

rail, the line which carries fuel to the engine. This device is critical to the smooth functioning

of an engine, as fluctuations in pressure can cause a variety of problems. To determinewhether or not the fuel pressure regulator is working properly, a test can be performed to

determine the fuel pressure; correct fuel pressure ranges vary, depending on the vehicle, and

they are often listed in the owner's manual.

If the fuel pressure is too high, it can cause an engine to run rich. This increases the emissions from

the vehicle, and it can cause clogging, racing, misfiring, and a variety of other problems. Low

pressure makes the engine run lean, in which case the engine may take a long time to start, if it

starts at all, and it may misfire, hesitate, or halt. Both of these circumstances are highly undesirable,

and the fuel pressure regulator prevents them from happening.

This device can sense the pressure in the fuel rail, and modify it with a flap which can be opened or

closed to decrease or increase pressure. If the pressure becomes extremely high, a valve opens toallow fuel to flow into a line which leads back to the fuel tank. A number of things can influence

fuel pressure, including leaks in the line and problems with the fuel pressure regulator.

If a car's gas efficiency radically declines, it has trouble passing emissions tests, or its engine is

running irregularly, it can indicate a problem with the fuel system, and the fuel pressure regulator is

an easy thing to test. A mechanic can usually test the device in a few minutes, determining whether

it is working properly or not. If the fuel pressure regulator is working, additional diagnostic tests

will be needed to track down the problem.

Having an engine which runs poorly is not just annoying. It also increases vehicle emissions, which

is bad for the environment, and it is hard on the engine. An engine's life may be shortened if it is

consistently run with the wrong fuel pressure, leading to potentially costly repairs or a catastrophicfailure in the future. If an engine starts to run rough, it's time to make an appointment with a

mechanic, or to take a look under the hood, for the mechanically-inclined.