CLUTCH - HOW IT WORKS - COMMON PROBLEMS

The clutch is an essential part of manual transmission systems. The hidden parts include a clutch plate, typically of 8" to 10" diameter, with friction material on both faces and splined to the gearbox input shaft. The clutch diaphragm is bolted to the engine flywheel; it is essentially a very strong spring which can clamp the clutch plate to the engine flywheel and force it and thus the gearbox input shaft to rotate with the engine. A clutch disengagement mechanism can release the diaphragm and allow the clutch plate and the engine to rotate independently for the purpose of changing gear.

The clutch pedal is connected to the disengagement mechanism either by a cable or, more commonly, by a hydraulic system. Either way, pushing the pedal down operates the disengagement mechanism which puts pressure on the fingers of the clutch diaphragm via a throwout bearing and causes the diaphragm to release the clutch plate. With a hydraulic mechanism, the clutch pedal arm operates a piston in the clutch master cylinder. This forces hydraulic fluid through a pipe to the clutch slave cylinder where another piston operates the clutch disengagement mechanism. The alternative is to link the clutch pedal to the disengagement mechanism by a cable.

COMMON PROBLEMS

Slippage: The Classic clutch symptom is slippage. The engine seems to race but the vehicle does not keep up and there would be partial or total loss of drive. Slippage is most often caused by a worn clutch disc. Or, the clutch pressure plate may be weakened by heat, age, or abuse, it means the vehicle needs a new clutch.

Less common causes of slippage include oil on the clutch, a broken disc or pressure plate, a release cable binding or transmission damage. Even when the problem is external you may still have to replace the clutch as Slippage causes almost instant damage to the clutch.

Clutch Release Problems: The symptoms of this would be difficulty in obtaining gear, particularly first and reverse gears. Sometimes there is an accompanying sound of grinding gears! When these symptoms occur, they are most often the result of the clutch not fully disengaging. The transmission input shaft is not allowed to come to a stop. Engine revolutions are still being transmitted to the transmission. Sources for this problem vary according to the type of clutch mechanism your vehicle has.

Mechanical Linkage: Worn pivot points, broken or bent push rod, worn or broken cross-shaft, bent pedal bracket, or cracked firewall can each cause this problem. Usually, several parts are contributing to the problem. This type of mechanism tends to wear and fail with age and continued use.

Cable Operated Clutch: Stretched, frayed or binding cable, broken or bent pedal bracket, or cracked firewall can be the cause. Problems with a cable mechanism will often herald internal clutch problems as well. When something happens inside the clutch that requires extra force to be exerted on the clutch pedal, things break! Cables can also wear simply from age and use.

Hydraulically Operated Clutch: Clutch master cylinder leaking or bypassing pressure, slave cylinder leaking, clutch flex hose leaking, pedal bushings worn or missing, or a cracked firewall can reduce the system's ability to disengage the clutch. Rule of thumb: If the clutch master cylinder is bad, replace both master and slave cylinders as a pair. This will save you future heartache.

Internal clutch Release Problems: Not all release problems are caused by the release mechanism. Things can go wrong inside the clutch as well. A loose damper spring in the clutch disc, bent disc, frozen pilot bearing, collapsed release bearing, or metal shrapnel from a broken cover can cause the clutch to bind and not fully release when the pedal is depressed. The release fork might bend. The pivot ball can wear or break. There are many reasons for a clutch to hang up.

Clutch Chatter: Clutch chatter, a shudder and vibration as the vehicle moves off from rest, is likely to be caused by an internal clutch problem. A warped friction plate, engine/gearbox mounts broken, hotspots on the flywheel or pressure plate surfaces, worn or dry input shaft splines, or worn release bearing. 

Q. I hear noises when operating the clutch.
         How do I know what they mean?

There are various noises that occur depending on the problem to correctly interpret the cause of clutch related noises, it is important to identify the type of noise, the exact condition under which they become evident and when they are silent.

     Squealing, scraping or crunching that starts when the
     clutch pedal is first depressed and continues until the
     clutch pedal is fully released:

          Usually caused by a frozen or damaged release bearing.
          The bearing may have failed on its own or may have
          been damaged by any of a number of associated failures.
          Replace the release bearing and the entire clutch kit. Be
          sure to check for wear of the metal sleeve on which the
          bearing slides and the shift fork and pivot ball.

     Scraping "rolling", or scraping noise when clutch pedal is
     fully released that continues until the clutch pedal is fully
     depressed:

          This one is usually expensive! The noise is in the
          transmission. In rare cases, it may indicate just an
          easily replaced transmission input shaft bearing. But,
          for most transmissions, even this small repair is not
          easy or inexpensive. And, this noise often indicates
          damage throughout the transmission.Requires
          transmission rebuild or replacement.

    Noises only in certain gears. Some gears are quiet. Silent or
     changes drastically when clutch pedal is fully depressed:

          Transmission! Internal wear, either bearings or gears.
          Indicates required transmission rebuild or replacement.

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BRAKES - HOW THEY WORK / COMMON PROBLEMS The typical brake system consists of brake discs in front and either disc or brake drums in the rear connected by a system of tubes and hoses that link the brake at each wheel to the master cylinder.  Other systems that are connected with the brake system include the handbrake, power brake booster and the anti-lock system. When you step on the brake pedal, the leverage pushes a small piston inside the master cylinder which forces hydraulic oil (brake fluid) through a series of tubes and hoses to the braking unit at each wheel. Since hydraulic fluid (or any fluid for that matter) cannot be compressed, pushing fluid through a pipe is just like pushing a steel bar through a pipe.  Unlike a steel bar, however, fluid can be directed through many twists and turns on its way to its destination, arriving with the exact same motion and pressure that it started with.  It is very important that the fluid is pure liquid and that there are no air bubbles in it.  Air can compress, which causes a sponginess to the pedal and severely reduced braking efficiency.  If air is suspected, then the system must be bled to remove the air. There are "bleeder screws" at each wheel cylinder and caliper for this purpose.   On a brake disc, the fluid from the master cylinder is forced into a caliper where it presses against a piston. The piston, in-turn, squeezes two brake pads against the disc (rotor) which is attached to the wheel, forcing it to slow down or stop. This process is similar to a bicycle brake where two rubber pads rub against the wheel rim creating friction.   With brake drums, fluid is forced into the wheel cylinder which pushes the brake shoes out so that the friction linings are pressed against the drum which is attached to the wheel, causing the wheel to stop. In either case, the friction surfaces of the pads on a disc brake system, or the shoes on a drum brake convert the forward motion of the vehicle into heat. Heat is what causes the friction surfaces (linings) of the pads and shoes to eventually wear out and require replacement. Renewing the pads or shoes as they wear is the most common requirement and frequent inspections are recommended. If the lining material wears excessively, it's not only extremely dangerous but inevitably other components become damaged calling for costly replacements. Fluid leaks are the second most common fault and can result in total brake failure.

Handbrake calipers - Handbrake not working properly.
Cause: Usually because the caliper has not been adjusted on installation or when pads have been replaced. The auto adjusting mechanism is only designed to gradually remove play as the pads wear down, not the major initial adjustment required.

Solution: Disconnect the handbrake cable, unbolt the caliper from its guide pins and firmly force the piston back to remove any play (put slight hand pressure on the caliper lever and you'll feel the play gradually disappear - stop at this point to avoid possible damage to the adjuster mechanism). Then, depending on type of adjusting mechanism (some have a hex key adjuster screw hidden behind a bung), wind the piston out so that the gap is just adequately wide enough to fit over the pads and disc. Refit the caliper and then press the brake pedal several times to let the auto adjuster remove any fine play still remaining. Finally reconnect the handbrake cable ensuring the caliper lever returns fully home when the handbrake lever is off.

Brake pedal creeps - Possible solutions.

There may be fluid loss caused by a leak somewhere in the hydraulic braking system. Urgent attention is required if regular top up of fluid is needed - because this indicates a leak!

Cause: If there is no loss of fluid, the problem will be caused by fluid being forced past a worn seal or a valve. This could happen in the master cylinder, ABS valve block, or pressure regulator valve.

Master Cylinder fault.
On a single circuit system (one outlet pipe), the fault is likely to be in the master cylinder. Pedal creep (with no loss of fluid) is unusual with tandem (twin circuit) master cylinders; but it may happen. The answer is to strip down the cylinder and check for damaged or contaminated seals or corrosion of the cylinder bore and rectify. It may be necessary to replace the cylinder.

Brake pedal creeps - Diesel engines.

Diesel engine vehicles usually use a pump to generate the vacuum for servo assistance. Unlike the inlet manifold of a petrol engine, there is no vacuum relief with a pump. If excessive pedal pressure is applied when the vehicle is stationary (and the engine is running) the hydraulic pressures required to stop the vehicle will be grossly exceeded and fluid will be forced past seals that are between circuits. Larger vehicles such as vans and 4x4s are more prone to this problem as they use servos with a higher boost ratio. The phenomenon is known as diesel creep; and it is often incorrectly diagnosed as being caused by a faulty master cylinder. The solution is to stop applying the excessive pressure.

IMPORTANT - If you can get the brake pedal to creep with the engine switched off and servo exhausted, or actually under braking there is a serious problem that requires urgent attention!

Brakes bind - Only after driving for a while.

Symptoms: Brakes are free at the start of a journey, but gradually bind or lock on as you drive.

Cause: When braking, heat is generated. This heat is transferred to the brake fluid. As the temperature increases, the fluid expands. Under normal circumstances, this expanded fluid returns to the master cylinder reservoir. If the expanded fluid cannot return to the reservoir, pressure builds up and applies the brakes; and more heat and more pressure are generated. When the fluid cools down, pressure reduces and the brakes release. Solutions: Take your tools with you and drive the vehicle until the brakes bind on. (The more they bind on, the more time you will have to diagnose the problem).

Follow these steps.

Step 1
With the brakes stuck on, slacken, by two to three threads, the nuts that hold the master cylinder to the servo. Then press and release the brake pedal. If the problem persists proceed to

Step 2
If the brakes are free after you've done this, the problem lies with the servo or the mechanical links to the pedal. Check that an incorrectly adjusted brake light switch is not holding the pedal on slightly. If the pedal has a link rod to the servo, check that this is well lubricated and moves freely. If the problem is not caused by the brake light switch or by the link rod sticking, it's possible that the link rod or servo push rod has been adjusted incorrectly. Otherwise, the servo is probably faulty.

NOTE Just in front of the master cylinder valve seals are small holes; these are compensating ports. With the brake pedal released, the master cylinder pistons should be fully home; otherwise the compensating ports will be blocked by the valve seals.

Slacken one pipe at the master cylinder for each circuit in sequence. (Use a rag to stop fluid squirting everywhere because brake fluid works like paint stripper). This will release any pressure in that circuit. If the problem persists proceed to Step 3. If the brakes release now, then it's highly probable that the master cylinder seals have swollen through contamination and are blocking the compensating/relief ports.

Step 3
Feel each wheel and start with the hottest wheel/brake first. Careful, things will be very hot! Slacken the bleed nipple/s on the caliper or wheel cylinder. If the brakes do not release, proceed to the next hottest wheel and repeat. When the brakes release, the problem is a faulty flexible hose attached to that wheel.

NOTE It is not uncommon for the inner wall of a flexible hose to collapse. When this happens, the collapsed wall can act like a one-way valve and can restrict the return of fluid.

Step 4
If the brakes are still stuck on, release the handbrake and start again!

IMPORTANT Remember to re-tighten all pipes/unions, nuts/bolts and bleed nipples.

Disc Judder problem - Cause/rectification.

Symptoms: Vibrations are felt through the car with a pulsating pedal when braking. If the steering wheel vibrates also, this tends to indicate the problem is with the front brakes.

Cause: Usually due to variations in disc thickness -

NOTE These variations in thickness are usually the result of excessive disc run-out, caused by mating the disc to dirty or distorted hubs. When driving (brakes off), the pads are normally in close contact to the disc. However, when there is excessive disc run-out, the pads scuff the 'high' parts of the disc on every rotation. This scuffing gradually wears the disc thinner where most contact is made. If you had a buckled bicycle wheel, the brake blocks would catch the wheel rim at the same 'high' points on every rotation. Disc run-out is similar, but the rotation speeds on cars are slightly quicker and brake pads are far more abrasive than a bike's rubber blocks. So when you've driven 2,000 miles, the pads have scuffed the same 'high' spots over two million times. Eventually the disc becomes thinner in two parts and causes a judder under braking. Simply replacing the discs without rectification will lead to the problem re-occurring.

Solution: Replace the damaged discs; but when doing so inspect the hubs properly and use a dial gauge to ensure disc run-out is less than 0.1mm (0.004"). This will avoid damaging the new discs. Alternatively, if the discs are only slightly worn, they can be machined on the car so that they run perfectly true.

Facts: If you fit new discs and they're great for the first 1,000-2,000 miles and then you start to notice a very slight judder developing, you've probably got DTV caused by run out.

If you fit new discs and they immediately judder, then it's probable (although very rare) that they have been machined incorrectly or there was a flaw in the casting.
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Your oil is pumped around your engine by an oil pump, which is usually in the bottom of the engine. The pump circulates your oil making sure it reaches all the components that need lubrication by forcing the oil through small passageways cut inside your engine, reaching the moving parts and protecting them. In this cycle the oil is pushed through an oil filter which collects all the small particles and debris and stores them until you have your filter changed. Each vehicle has different intervals stated by the manufacturer of when the oil filter should be changed.

Oil
10W/40 - What does that mean? 10W/40 is a classification used to describe the viscosity (thickness) of an engine oil. The viscosity is the most important factor to consider when buying oil since this number ensures that adequate lubricating films exist between the working parts. 10W - where "W" stands for winter, describes the flow of oil from cold start and reflects how quickly the oil is able to flow around the engine. Since most wear and friction occurs from cold starting, most vehicle manufacturers agree that low viscosity oils i.e. 0W-5W-10W-15W-20W etc. are the best option. 40 - Relates to how the oil flows at full operating temperatures and describes the ability of the oil to provide adequate film strength when the engine is hot i.e. separate sliding metal surfaces.

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TIMING BELTS - HOW THEY WORK

Certain engines with overhead camshafts have timing belts that have a limited life span. Manufacturers use these belts instead of more durable chains because chains are noisier and cost more to manufacture.  Your vehicle owner's manual will recommend at what mileage the timing belt must be replaced, but you can also check with your local dealer for up to date information.

The job of the timing belt is to turn the camshaft(s) at exactly 1/2 the speed of the crankshaft while maintaining a precise alignment.  This means that the crankshaft will make two revolutions for every revolution of the camshaft.  Engines will have at least one camshaft, or as many as four camshafts in some of the V-type engines.  The camshaft causes the intake and exhaust valves to open and close in time with the pistons which move up and down in the cylinders.  The valves must open and close at exactly the right time in relationship to the piston movement in order for the engine to run properly

There are two types of engines that use timing belts.  They are described as: "Interference Engines" and "Non-interference Engines" The difference lies in the proximity between the valves and the pistons.  On an interference engine, if the timing belt slips even one notch, the piston can crash into an open valve causing serious engine damage by bending valves and breaking pistons.  Non-interference engines will usually not self destruct, but in either case if the belt fails, the engine will immediately shut down leaving you stranded. 

Timing belts fail without warning and on some vehicles, are almost as hard to check as they are to change.  In most cases, your only protection is to change the belt at the recommended intervals. Timing belt replacement is not a cheap job but it is far less costly than the alternative.

You may think about replacing the water pump during a timing belt job even if there is nothing wrong with it.  This is because 90% of the laboUr to change the water pump has already been done with the timing belt job. Some water pumps can last the life of the car but many do fail and will cost big money to replace at a later date.
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 RECOMMENDED WEEKLY VEHICLE CHECKS

Although many modern vehicles are low maintenance, weekly checks are important to avoid major damage to your engine. If the engine has been running for any length of time, there are areas under the bonnet that can be very hot. Except for checking automatic transmission fluid level, all checks should be done while the engine is turned off. If the engine is running, do not put your hands near any belts or fans

Engine oil level

This is the most important under-bonnet check you can do.  An engine cannot run without oil even for a minute without serious engine damage or total destruction!
To check the oil level, make sure that the engine is turned off, allow a few minutes for the oil to settle then find the engine oil dipstick and remove it. With a paper towel or rag, wipe off the end of the stick and notice the markings on it. You will usually see a mark for "Max" and another mark for "Min." Check your owners manual to be sure. Push the stick back into the tube until it seats then immediately pull it out to see the oil level. Add Oil to bring the level to the "Max" mark and NEVER add oil to bring the level above the "Max" mark.
Your main concern with this check is that oil consumption is not rapidly increasing. It is acceptable for the oil to be dark as long as you change it at the recommended intervals. However, it should never be foamy and should never have a strong petrol smell.

Brake fluid
The brake fluid reservoir is under the bonnet right in front of the steering wheel. Most cars today have a transparent reservoir so that you can see the level without opening the cover. The brake fluid level will drop slightly as the brake pads wear out. This is a normal condition and you shouldn't worry about it. If the level drops noticeably over a short period of time or goes down to about two thirds full, check your brakes as soon as possible. NEVER PUT ANYTHING BUT APPROVED BRAKE FLUID IN YOUR BRAKES. ANYTHING ELSE CAN CAUSE SUDDEN BRAKE FAILURE!
Keep the reservoir covered except for the amount of time you need to fill it and never leave a can of brake fluid uncovered. Brake fluid must maintain a very high boiling point. Exposure to air will cause the fluid to absorb moisture which will lower that boiling point.

Power steering fluid
The power steering fluid reservoir usually has a small dipstick attached to the cap. Remove the cap and check the fluid level. The level should not change more than the normal range on the stick. If you have to add fluid more than once or twice a year, then check the system for leaks. These systems are easily damaged if you drive while the fluid is very low. Another warning of low power steering fluid is a buzzing noise when you turn the steering wheel at slow speeds.

Coolant (Antifreeze) level
Never open the radiator of a car that has just been running. The cooling system of a car is under high pressure with fluid that is usually hotter than boiling water. Look for the cooling system reserve tank, somewhere near the radiator. It is usually translucent white so you can see the fluid level without opening it. (Do not confuse it with the windscreen washer tank). The reserve tank will have two marks on the side of it. "FULL HOT" and "FULL COLD." If the level frequently goes below "full cold" after adding fluid, you probably have a leak which should be checked as soon as possible. Today's engines are much more susceptible to damage from overheating, so do not neglect this important system.

Battery
Most batteries today are "maintenance free" which simply means that you can't check the water level. This doesn't mean however, that there is nothing to check. The main things to check are the top of the battery which should be clean and dry, and the terminal connections which should be clean and tight. If the top of the battery continuously becomes damp or corroded soon after cleaning, then check the charging system and battery.

Windscreen washer solvent Windscreen Washer Solvent is fine to use with or without adding water but will clean better undiluted. Never dilute it during winter months to insure that it retains its antifreeze protection.

Automatic Transmission Fluid
Most automatic transmissions should be checked while the engine is running. Check your owners manual to be sure. Also make sure the car is on a level surface and fully warmed up. Pull the transmission dipstick out, wipe off the end and note the markings on the end of the stick. Push the stick into the tube until it seats, then immediately pull it out to see the fluid level. Transmission fluid should be pink or red in color with the look and consistency of cherry cough syrup.  If the fluid is a muddy brown or has a burnt smell, check the system. Add fluid to bring it above the "Min" mark and never bring it above the "Full" mark. Make sure you use the correct transmission fluid for your vehicle. You will need a special funnel to get the fluid into the small tube that the dipstick came out of.  Check your owners manual for the type of fluid and do not substitute anything else.
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 FUEL SYSTEM - HOW IT WORKS

The function of the fuel system is to store and supply fuel to the cylinder chamber where it can be mixed with air, vaporized, and burned to produce energy. The fuel, which can be either petrol or diesel is stored in a fuel tank. A fuel pump draws the fuel from the tank through fuel lines and delivers it through a fuel filter to either a carburetor or fuel injector, then to the cylinder chamber for combustion.

FUEL FILTERS

The fuel filter is the key to a properly functioning fuel delivery system. This is more true with fuel injection than with carbureted cars. Fuel injectors are more susceptible to damage from dirt because of their close tolerances, but also fuel injected cars use electric fuel pumps. When the filter clogs, the electric fuel pump works so hard to push past the filter, that it burns itself up. Most cars use two filters. One inside the fuel tank and one in a line to the fuel injectors or carburetor. Unless some severe and unusual condition occurs to cause a large amount of dirt to enter the fuel tank, it is only necessary to replace the filter in the line.  

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COOLING SYSTEM - HOW IT WORKS

RADIATOR: Cools off the anti-freeze/coolant mixture by allowing air passing through the tube/fin area to dissipate the heat generated by the engine.

WATER PUMP: Draws the cooled anti-freeze from the radiator and pumps it through the engine block, cylinder head(s), heater core and back to the radiator.

FREEZE PLUGS: Is actually a steel plug designed to seal holes in the engine block and cylinder head(s) created from the casting process. In freezing weather they may push out if there is not enough anti-freeze protection.

HEAD GASKET /TIMING COVER GASKET: Seals the major parts of the engine. Prevents oil, anti-freeze and cylinder pressure from mixing together.

HEATER MATRIX: Provides heat to the interior of the car by using heat removed from the antifreeze and blown in by the heater motor. May cause steam, odoUr or actual dripping inside the car when it leaks.

THERMOSTAT: Controls the minimum operating temperature of the engine. The thermostat is closed when the engine is cold in order to speed warm-up and opens when normal operating temperature is reached to allow the anti-freeze / coolant to pass through the radiator.

HOSES (Radiator, Heater, By-pass): Connect the other main components of the cooling system. Hose manufacturers recommend replacing every 4 years regardless of appearance because there may be deterioration of the inside of the hose which cannot be seen.

FAN CLUTCH: Senses the temperature of the air coming through the radiator and either slips or binds up to pull the required amount of air through the radiator.

ELECTRIC COOLING FAN: Most front wheel drive cars use this because of the transverse mounted engine. It is turned on by a system of sensors and relays when the engine reaches about 230° F and stays on until the radiator is cooled to about 200° F.

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STARTING SYSTEM - HOW IT WORKS

The "starting system", the heart of the electrical system in your car, begins with the Battery. The key is inserted into the Ignition Switch and then turned to the start position. A small amount of current then passes through the Neutral Safety Switch to a Starter Relay or Starter Solenoid which allows high current to flow through the Battery Cables to the Starter Motor. The starter motor then cranks the engine so that the piston, moving downward, can create a suction that will draw a Fuel/Air mixture into the cylinder, where a spark created by the Ignition System will ignite this mixture. If the Compression in the engine is high enough and all this happens at the right Time, the engine will start.

 SHOCK ABSORBERS - HOW THEY WORK

When a spring is compressed and then released, the energy within the spring causes it to continue to flex up and down before it settles to its original shape. Going over a bump in your car compresses the springs, so the car would also continue to bounce up and down making the car difficult to control. The effect of the shock absorber is to dampen the spring's natural reaction to bounce.
	Shock absorbers are filled with hydraulic fluid. When the 'shocker' is compressed, this fluid is forced by a piston through a small hole in the shock absorber cylinder and into the other end of the unit. The design prevents this action happening quickly, so the spring is restricted from continuing to bounce, helping to keep all four tyres in good contact with the road surface.

If you want to check whether your shock absorbers need replacing, try this simple 'bounce' test. Press down on one corner of your car and let go. Count the number of bounces before the car comes to rest. If the car bounces even twice, your shock absorbers are faulty and should be checked straight away.

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