How shock absorbers work in car

Even though shock absorbers have been in use since the early days of the automobile, they are not well understood by the general driving public. Even automotive enthusiasts will neglect and often ignore the shock absorbers on their car, degrading the car’s handling performance and ride comfort.

Even worse, worn shocks can be dangerous, especially during the severe maneuvers that might be necessary to avoid an accident. As we will see, for such a simple yet effective device, shock absorbers seem to get little respect.

The gravity of the situation
Strangely enough, despite their name, shock absorbers don’t absorb shocks. In reality, that is the job of the springs in a vehicle’s suspension system. As a wheel encounters a bump, the wheel moves upward, compressing and storing the energy of the bump into the spring. This compression is actually what absorbs the shock of the bump.

But now that the spring is compressed, it contains potential energy that must be released. The spring does this by bouncing back to its original uncompressed length, at the same time pushing the vehicle’s body upward. In an example of the old adage “what goes up, must come down,” gravity pulls the weight of the body back down, recompressing the spring. If the shock absorbers are worn, the vehicle ends up bouncing its way down the road after every bump until all of the energy is used up. In the worst cases, this bouncing can actually pull a vehicle’s tires off the ground, making the vehicle uncontrollable.

Bring on the dampers
Shock absorbers, more properly called dampers, are mounted alongside (or inside) the springs at each corner of the vehicle. A shock absorber’s job is to provide resistance to the movement of the spring. Technically speaking, it does this by taking some of the energy that is being used to compress the spring and turning it into heat. So whether the vehicle is bouncing up or down from a bump in the road, that motion is held in check by the shock absorber, and once again some of the kinetic energy released by the spring is changed into heat by the shock absorber. This conversion of energy keeps the vehicle’s body from bouncing more than once or twice, providing a controlled ride and helping to keep the vehicle’s tires safely in contact with the ground.

How do shock absorbers work?
If you have ever waved your hand back and forth through water, then, in principle, you know how a shock absorber works. The resistance to motion you feel with your hand changes with speed – the faster you move your hand, the more energy it takes to push against the resistance of the water.

A shock absorber works much the same way. Inside the shock absorber there’s a piston that moves inside a tube that is filled with oil. As the piston moves, the oil is forced through tiny holes and valves within the piston, precisely controlling the amount of resistance to movement. This resistance to the motion converts the energy into heat. (Yes, a shock absorber that has been doing its job over a rough road does get warm!)

Although there have been many different designs for shock absorbers over the course of automotive history, today there are four basic types available:

• Twin-tube
• Mono-tube
• Gas-filled mono-tube
• External reservoir

Sometimes these types of shock absorbers are incorporated into a strut-type suspension that uses the shock absorber as part of the spring support, but the basic principles still apply.

Twin-tube shocks
The twin-tube design is the most common and often the least expensive. These are the ordinary shock absorbers that typical passenger cars and trucks use, and they are widely available at car dealerships, auto parts stores and repair facilities. As the name implies, in a twin-tube shock, there are two actual tubes – one the outer shock body and the other an inner cylinder in which the piston moves. Tiny holes or orifices in the piston as well as special valves between the inner and outer tubes restrict the flow of oil to control wheel motion.

The limitations of twin-tube shocks become apparent when they are used over very bumpy roads. In this case, the rapid motion of the piston can cause the oil to overheat and to foam, reducing the shock absorber’s ability to control wheel motion. The result is a ride that becomes increasingly sloppy, especially when traveling over a washboard surface. Heavy-duty twin-tube shock absorbers are usually stronger, with more robust piston shafts and mounting points, and they may use oils that are more resistant to foaming, but ultimately they still have the same limitations.

Mono-tube shocks
The heat generated in the twin-tube shock tends to get trapped within the walls of the shock absorber body, reducing its effectiveness in controlling wheel motions. The mono-tube shock absorber uses a piston traveling within a single tube that is exposed more directly to the air. The general advantages and disadvantages of this design are:

• By getting rid of heat more easily, mono-tube shocks are less susceptible to overheating on rough roads.
• They are more expensive to manufacture, and the tolerances must be higher and the seals better to keep the oil inside the shock body.

Gas-filled mono-tube shocks
To prevent foaming and bubbles in the oil, which degrades shock-absorber performance, a gas-filled mono-tube shock has a chamber of high-pressure nitrogen above the oil chamber. This high-pressure gas makes it difficult for bubbles to form in the oil, even when the shock absorber moves in and out very quickly, as it might while traveling rapidly on a very rough or washboard road.

Gas-filled shocks are expensive, since they require strict manufacturing tolerances, but they are very resistant to fade and consequently are popular in off-road racing and rallying. Gas-filled shocks, by the way, are not the same as “air shocks,” which use an air chamber separate from the shock oil. An air shock is actually an air spring that raises or lowers the vehicle when air is added or removed through a valve.

External reservoir shocks
The top of the line in shock absorbers is the external-reservoir design. These shocks, primarily designed for ultra-high performance and racing applications, use a small, lightweight shock body that is connected through a hose to a reservoir of oil mounted in a different part of the vehicle. The goal of an external reservoir shock is to:

• Reduce the weight at the wheel for better handling
• Provide better cooling for the oil in the reservoir
• Provide significant air space within the reservoir so that the hot oil can expand without blowing out seals
• Allow superb adjustability as the oil flows to and from the shock body

External reservoir shocks are very expensive and are really only needed in extreme high-performance applications.


When to buy shocks
Shock absorbers last a long time, but they tend to degrade slowly throughout their life. So when is it time to replace them?

• In some cases, a seal will rupture. A shock covered in oil is a good indication that it has failed.
• The age-old test of bouncing on a fender is really only a rough guide as to whether your vehicle needs new shocks.
• Usually the slow degradation in your shock absorber’s performance won’t be noticed until it affects handling fairly dramatically.
• Depending on how rough your roads are, modern shocks can last 80,000-100,000 miles, but remember that a shock with 60,000 miles on it won’t perform as well as a new one.

Shocks can be tested on a shock machine, but to do so requires them to be taken off the car. With labor rates what they are, if your mechanic already has the old shocks off, it makes sense to replace them with new ones.

Replacing worn-out shocks can revitalize the handling of a vehicle, returning much of the crispness it had when new. When combined with a new set of tires, new shocks can transform a high-mileage vehicle with sloppy handling and a bouncy ride.

Choosing shock absorbers for your vehicle
Choosing which shocks to buy largely depends upon what kind of vehicle you own and the kind of driving you do.

• Shocks are available in a range of prices. Often you get what you pay for.
• If you liked the way your vehicle rode and handled when it was new, go with original-equipment replacements.
•  If you are looking for more, there are a variety of options open to you, including heavy-duty shocks for carrying heavy loads and performance shocks for crisper handling.

As with most automotive components, it is important that you buy the right shocks for your specific vehicle, since mismatched shocks can drastically affect handling and could even be dangerous. The best advice will probably come from a mechanic who is familiar with your type of car. It goes without saying that if you make the right choice, the improvements in your vehicle’s ride and handling can be shocking!

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What Does It Mean When Your Spark Plug Wells Are Filled with Oil?

I recently pulled out the spark plug wire and found there is engine oil in the plug well. This problem has me worried and I need advice. Is it a big problem I should get fixed right away?
Answer: Repair Oil Leaks Into the Spark Plug Wells As Soon As Possible

There is an O-ring that seals the spark plug well and keeps oil from leaking into it. As with any valve cover gasket, it will start to leak over time. Sometimes tightening the valve cover bolts will stop the leakage, but more often than not the valve cover gasket, and well seals, will need to be replaced.

The seals will come with the valve cover gasket set. I would get it fixed as soon as possible. The oil will cause the spark plug boot to swell and lead to a misfire. This will certainly hurt engine performance as well as a possible engine fire.

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10 WAYS TO KEEP YOUR CAR RUNNING AND LOOKING BEAUTIFUL

Whether you bought it new or willingly took it off of Pop-pop's hands, your automobile deserves TLC. If your vehicle looks and runs bad, you look bad. To ensure your car (and you) remain looking and running cool, we spoke with Valvoline Senior Scientist Erin Findley to help with 10 essential maintenance tips.

1. Change your oil regularly -- and use the right oil
“Engines are smaller today, but they’re doing more, so oil is expected to handle those higher demands,” says Findley. What’s that mean in real talk? Though engines are more powerful and efficient, changing your oil is as vital as ever if you want to extend the life of your car. So how often, and when should you do it? To find out…

2. Read the damn manual
“Most of the time when people say they know better (about choosing a particular grade of motor oil), they don’t,” says Findley. “Manufacturers have spent millions on knowing what type of oil is the best for a particular car. By choosing the wrong one, you could increase wear and lose fuel economy.” Pay attention, Findley says, to the definition of “severe driving” in your particular model’s manual. “Most people think they’re ‘normal drivers’ and follow what they perceive as normal guidelines, but they don't read the manual.  If you look at what the definition of "severe driving" is, most people fall into that category which consists of lots of short trips in stop and go traffic, or living in dusty, hot, or cold conditions.”

3. Change your wiper blades
Would you go on a date with your specs covered in grease from your sweaty mitts? No? Then you shouldn’t drive around town with a windshield that’s slowly taken on a layer of grime, thanks to deteriorating rubber blades. Most experts recommend swapping your old wiper blades out for new ones every six months. The cost (between $10 and $25) is worth it -- for a clearer, prettier Instagram-worthy sunset view -- but only from the passenger seat, of course.

4. Inspect your tires regularly
Yeah, we are about to get all fatherly up in here. Like Dad always said: bald, worn out tires provide less control on the road, and worse braking. Turn to a founding father -- Abe Lincoln -- to see if yours need replacing. Grab a penny and put it Lincoln-head down in one of the tread grooves, if part of Honest Abe’s head is always covered by rubber, you likely don’t need need to replace your tires. If you can see all of Abe, it’s probably time for a fresh set.

5. Maintain your brakes
It shouldn’t need to be said, but never neglect the warning signs that your brakes need care. Even if you don’t see a brake warning light, hearing squeaking, squealing, or other odd noises coming from your brakes might mean that your pads or rotors need to be replaced. Don’t just turn up your music to try to drown out the sound -- deal with it!

6. Change your air filters annually
Before the magic of internal combustion begins, an air filter prevents dust and debris from getting into your engine, where oxygen and fuel meet to make sweet, sweet love. Like a bouncer outside of the backstage. But when it’s clogged, an air filter can’t do its job properly, and your car’s ability to accelerate can be cut by as much as eleven percent. That’s why it’s vital to change yours at an annual interval, or earlier, if your manufacturer recommends it.

7. Use the right fuel
If your car's owner's manual doesnt call for premium fuel, don't use it -- higher octane fuel doesn't provide higher performance for engines that don't need it. Again, read the manual to find out what your car requires. But that doesn’t mean you should buy the most bargain-basement gas you can find from some off-brand station you've never heard of. “When you’re using the cheapest gas in town, you could be getting what you pay for,” says Findley.

8. Watch your coolant
Coolant absorbs the heat of the engine and disperses it. Seriously, you should have it flushed once a year with a mix that’s fifty percent coolant, fifty percent distilled water to ensure endless chill for your ride.

9. Maintain your battery
The phrase “Looking good, feeling good” doesn’t just apply to your gym routine -- it applies to your car battery too. Dirt and oil can drain your battery’s current and shorten its life, so treat it to a shammy. Check the terminals for corrosion and apply a mixture of baking soda and water if they’re crusty.

10. Don’t use dish soap to wash your car 
You don’t use dishwashing soap to wash your princely mane in the shower and you shouldn’t use it to wash your car, either. Dish soap’s abrasive nature wears down the finish of your car and can lead to a dull sheen and oxidized paint. Most car soaps are pH balanced and can give your ride the sweet caress it deserves.

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How to change brake pads?

Replacing brake pads on disc brakes is far easier than the job used to be on drum brakes. However, it’s always good to know what you’re doing beforehand. Read the instructions fully before you get started.

Tools and materials:

• Replacement brake pads and any hardware that comes with them
• Jack and jack stands
• Lug nut tire tool
• Socket set with ratchet (open-end wrenches also work)
• Stout, straight-edged screwdriver
• Hammer and punch
• Pliers
• Pry bar (tire tools also work)
• Wire brush
• Aerosol brake cleaner
• Brake fluid (just in case)
• Thread-locking compound
• Five-gallon pail or other waterproof container of similar size
• Rags to catch fluid spills under master cylinder
• Inexpensive turkey baster

Types of disc brake systems

Unfortunately, all disc brake systems are not the same. But they are similar enough that we can generalize quite a bit here. The two main types are fixed calipers and moving calipers ("floating" or "sliding"). Fixed calipers are the easiest, as you do not have to remove the caliper to get to the pads. After disconnecting any electrical wear sensors, remove a small pin or spring clip and pull out the pads with a pair of pliers. Some of these systems have the pads secured by a pin that must be driven out with a hammer and punch; most systems are no longer of this simpler type. With moving calipers, the caliper is either removed or flipped up, rotating on the top pin, which is left in place.

How-to tips

If the brake fluid was topped off when the pads were worn, there may be too much fluid in the system to support the new, thicker pads. Leaks can occur under the hood. Some fluid can be drained from the reservoir with a vacuum pump or simply with a turkey baster. Or you can use rags under the master cylinder to catch minor spills. Loosen the reservoir's cap and proceed to the first wheel.

Whether you are servicing the front or rear of the vehicle, you should do both sides, never just one. But do them from start to finish – one at a time. The first reason for doing one at a time is so you can more effectively monitor the fluid level as you work. You’ll find out the second reason soon. Make sure to secure the vehicle in position and remove the lug nuts (both wheels). After the vehicle is jacked up and stable on the jack stands, finish loosening the lug nuts and remove the first rim. Now you can really get started. For vehicle-specific brake pad replacement procedures, always consult a service manual.

The general procedures for most systems are as follows:

1. Disconnect any electrical wear sensors.

2. Using a socket wrench, remove the two long guide pins ("slider bolts"), usually accessed on the back of the caliper. On front wheels, they are easier to see if you turn the steering wheel toward the other side of the vehicle. To loosen the caliper, you may need to pry it slightly with a sturdy screwdriver. Again, with some systems, you may be able to remove only the bottom pin and flip the caliper up over the top pin. But whether you flip it up or remove the caliper, take care not to stress the brake hose. If removing the caliper, use the five-gallon pail, inverted, to support the weight of the caliper.

3. The pads are now exposed. If present, remove any clips, anti-rattle springs and anti-squeal shims. Some pads have tabs that are bent over. You may need to straighten them with pliers before removal. And now the second reason for doing the brakes one side at a time: You have the other side to refer to if you lose track of where any of the hardware came from.

4. Remove the old pads with pliers or a light hammer tap.

5. Dust the caliper sliding area with a wire brush and spray brake cleaner. Note: Never use high-pressure, compressed air on brake dust, as it contains asbestos and should not be inhaled.

6. Lightly lubricate the same area with heat-resistant brake grease. Be careful with the lubricant, not allowing any of it to come into contact with the swept area of the rotor, or getting any on the new brake pads.

7. If your system is equipped with hardware such as clips, they should be included with your new pads, especially if you get Original Equipment Manufacturer (OEM) parts. There may also be a packet of grease.

8. With the old pads out, the internal pistons are exposed. They need to be retracted back into the caliper. Your vehicle may have two pistons. If so, be sure to compress them both at the same time. Pressing one could pop the other all the way out, which is a bad thing. Reposition one old pad back into place and tighten the large C-clamp on it to retract the pistons. You can also use a piece of two-by-four and a pry bar to push them back. Or, if you only have one piston, just use a pry bar with a rag around the end. The piston(s) need to be fully retracted to fit over the rotor, but take care not to damage their rubber seals.

9. Compression of the piston into its bore forces fluid back into the master cylinder's reservoir. This is when leakage may occur if too much is in the system for the new, thicker pads. Check the reservoir, particularly after you finish the first wheel. You should be able to tell if the second wheel is likely to force too much fluid into the reservoir, so you can remove some fluid ahead of time.

10. Insert the new pads, replacing any hardware you removed with new parts, if available. If yours are the bent-tab style of pads, you have to ensure a snug fit. If it is not snug, adjust the tab lightly with a hammer until you have a tight fit.

11. Reposition the caliper over the rotor and secure it with the long guide pins. Use a thread-locking compound on the pins' threaded area to ensure a secure fit.

12. Reconnect any electrical wear sensors. Now refer back to step one on this list to start work on the second wheel. Once the second wheel also has new pads, please proceed to step 13.

13. When finished, pump the brake pedal several times to seat the new pads. The brakes won't stop the vehicle until the pads are properly seated. Recheck the reservoir for proper fluid level and adjust.

14. Install wheels and tighten the lug nuts to just snug.

15. Lower the vehicle and fully tighten the lug nuts. Note: You must use a torque wrench to properly tighten your lug nuts. The ft-lbs specification necessary for your vehicle will be located in the owner’s manual.

16. It’s time for a road test. Remember, don’t forget to seat your new pads or to properly tighten lug nuts before driving off.

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Different types of oil filters and how they work

Oil is the lifeblood of the engine in your car or truck (or motorcycle, boat, airplane, tractor and so on). Plain and simple. But as the oil circulates through the engine, it picks up any number of contaminants (in simple terms, dirt). That dirt can obviously damage your engine. And over time, that dirt can bring the engine to its death.

How do oil filters work?
Early internal combustion engines did not use oil filters and, coupled with the poor quality of oil available at the time, vehicles required frequent oil changes. Eventually, the first full-flow oil filtration system was developed. Basically, this arrangement allowed for the oil to flow through the filter before it reached the critical working components inside the engine.

So far so good, but there was (and still is) a big caveat: The vast majority of pressurized lubrication systems found in internal combustion engines incorporate some form of filter by-pass to protect the engine from starvation under certain circumstances. A good example is very cold weather. In this situation, if the oil is too thick, it is allowed to bypass the filter. Oil can also bypass the filter when the filter is plugged. Because of these events, oil is sometimes not filtered, even when the engine is fitted with a full-flow oil filter.

In operation, oil enters the oil filter through a series of small holes on the outer edge of the base flange. The oil is then directed through the filter, eventually making an exit into the engine through the large center hole. Most modern oil filters are equipped with an anti-drain back valve. This is often some form of rubber membrane that covers the perimeter holes in the base flange. The membrane is forced aside as oil enters the filter case. When the engine is not running, the rubber membrane covers the holes. Obviously, the anti-drain back valves maintain oil within the filter. In turn, they prevent engine dry starts (when the engine is started with no oil).

Early oil filter designs
Early oil filter designs were based on a replaceable element fitted inside a metal housing. When changing the filter, one removed the housing, discarded the element, cleaned the housing, added a new filter and re-installed the assembly to the engine. By the mid-20th century, spin-on filters gained popularity. Here, the filter element and the cartridge are self-contained. You simply remove the works, discard it, and screw on a new filter during the oil-change process. Today, there's been a move back to the earlier oil filter design. In this system, oil is filtered through an element contained within a separate housing, because the replaceable filter element may be more environmentally conscious than a spin-on filter. Keep in mind that today's motor vehicles require far fewer oil changes than those of yesteryear.

Today’s oil filter types
There are many types of oil filters available today, and there are likely an equally large number of tests in which various filters are cut apart and diagnosed. The truth is, all oil filters are not created equal. The bottom line: You usually get what you pay for.

But are there any real differences between standard filters, high-performance filters, race filters and synthetic filters? Absolutely.

You have to first consider the mission of the motor vehicle. Case-in-point is a racecar. Here is something that will seldom, if ever, experience cold starts (in many cases, the oil is warmed prior to starting). Oil is changed frequently, simply because the engines are inspected and regularly disassembled. Oil in racecar engines was once far thicker than that found in passenger cars, but today it's just the opposite. Racers have discovered the benefits of light oil.

Without going into detail, it's not uncommon to find race engines filled with oil as light as zero grade. Racing filters are engineered to work with those oils. Some race filters are not fitted with drain back valves.

On the other hand, many racing oil filters are engineered with an internal media that is resistant to high temperatures and water levels in the oil that can plug standard oil filter media types. Many racing oil filters are engineered to provide high levels of oil flow with low restriction. Certain racing oil filters engineered for use in endurance applications (for example, 12- or 24-hour races) contain a different media that is designed to trap smaller contaminants.

Some race or high-performance filters are built with more robust cases to protect against damage from track debris. Heavier base plates are also incorporated in some of these filters. This ensures that the filter body does not flex under high-pressure conditions. Some are constructed so they can be safety-wired to prevent accidental loosening. A few of the high-performance filters also incorporate rolled threads instead of cut threads to ensure the filter doesn't strip during installation.

Paper or plastic?
Filter media is another difference. Some filters are engineered with synthetic filter media (rather than pleated paper-based media). The synthetic media is said to be capable of trapping small contaminants over a longer period of time (higher miles). Additionally, some synthetic filters include special blends of rubber for gaskets and drain back valves. The purpose? Like the filter media, they're designed to last longer. Finally, some synthetic filters actually have larger (typically longer) bodies than conventional filters, which means they have more capacity. Because of these factors, some synthetic oil filters have service lives of anywhere from 7,000 to 25,000 miles.

As you can see, there are plenty of variables found inside oil filters. So what's right for your car, truck, motorcycle or other vehicle fitted with an internal combustion engine? The answer is, it depends. You really need to carefully study the specifications of each filter to determine the suitability for your particular application. If your vehicle is newer, you should also give some serious consideration to the warranty. Some filters may not be deemed compatible by the vehicle manufacturer, and that's important when it comes to a warranty claim.

The reality is, you might want to think twice before using high-grade synthetic oil and a top-of-the heap high-performance oil filter in a thrashed beater. And, similarly, it doesn't make much sense to use the cheapest oil and filter possible in a collectable Ferrari. In the end, selecting a filter is much like selecting oil. Pick the one that best fits the application and your budget.

The filtered facts

• The car oil filter required for the vintage six-cylinder Buick is far different from the one found on the 7,000 (or more) horsepower Top Fuel dragster. In both cases, the mission is the same: Keep the oil clean.
• Filters are not created equal. The intended application for a given oil filter has a big impact on the design and engineering of the component. Internally, a racecar’s oil filter is far different from a passenger car’s filter.
• In a typical passenger car engine, oil enters the filter at the filter pad, most often part of the engine block. From here, it circulates through the series of smaller holes in the outer perimeter of the filter. At this point, oil is forced through the filter element (from the outside, in) and eventually is forced toward the center of the filter (going back into the engine through the large threaded hole below the pointer).
• When a filter does its job, internal engine components – such as the connecting rods, camshaft and valve train – are protected from contaminants that can cause major damage. These components are expensive. Picking the right oil along with the right filter can definitely promote long engine life.