Can You Answer All of These Questions an Auto Mechanic Should Know?
By: Justin Cupler
After any suspension or chassis work, a vehicle needs what?
After disassembling the chassis or suspension, the alignment will be way off. Performing an alignment after any suspension or chassis work is a requirement. Without this, the vehicle may be unsafe to drive.
What are the telltale signs of internal transmission issues?
Any mechanic can identify internal transmission issues from the fluid alone. Black fluid indicates worn-out internal clutches. Sticky fluid indicates overheating. Smelly fluid indicates high heat that caused the fluid to burn.
What is a telltale sign for overinflated tires?
An overinflated tire tends to bulge in the center of the tread. This puts most of the car's weight on this center section and causes it to wear out prematurely.
What is the correct pattern for torquing a wheel?
You should always tighten lug nuts in a crisscrossing pattern. This ensures you tighten the wheel evenly and avoid stretching or weakening the wheel studs.
What is a Road Force balancer?
A Road Force balancer is a special machine that applies force to the tread of the tire for more effective balancing. It can also detect flaws in a rim and tire, and recommend match-mounting the tire and wheel to offset these imperfections.
What’s it mean to “turn” a rotor?
Turning a rotor means to put it on a lathe and shave off small amounts of material to remove any imperfections. This helps prevent vibration and decreases stopping distances by giving the brake pads a rough surface to grip. Every brake job should include turning or replacing the rotors.
What is a parasitic draw?
A parasitic draw is a small electrical issue that pulls a small amount of power from your battery when the vehicle is off. Under normal operation, you likely won't notice an issue, but if it sits overnight or for a few days, it could kill the battery.
What is the name of the orange-colored coolant General Motors cars use?
GM began using Dex-Cool -- a silicate-free, orange-colored coolant -- in the 1990s. While this coolant was supposed to be a longer-lasting alternative to the green stuff, there have been numerous complaints and lawsuits surrounding corrosion and co0ling-system clogs causing major damage.
A car comes in with a slipping transmission and the customer wants a transmission flush. What should you do?
When a transmission starts slipping, this means there is already internal damage. Forcing new fluid into the transmission can actually cause more damage or even lead to complete transmission failure.
Transmission fluid has three main functions. What are they?
The transmission fluid not only lubricates the transmission's moving parts, but it also acts as the hydraulic fluid and washes away any loose debris. Failure of any one of these functions can result in serious transmission damage.
What’s the significance of the D.O.T. number on a tire?
The D.O.T number shows the factory and batch numbers, and the manufacture date of your tires. This way you know how old they are and the manufacturer can easily issue recalls for select batches of tires.
What is a directional tire?
A directional tire's tread is designed to only roll one direction. These are typically high-performance tires with asymmetrical tread patterns. These tires will have an arrow pointing in the direction they are supposed to roll.
What are the three main types of brake pads?
They are organic, semi-metallic and ceramic. Organic pads are typically cheapest, and are a mixture of natural materials, like glass, rubber and more. Semi-metallic pads mix in metallic fibers for longer life and better stopping power. Ceramic pads replace the metal fibers with ceramic ones to reduce brake dust.
What should you always wear when installing a replacement light bulb?
The oils on your fingers can transfer to the light bulbs on installation. These oils can get very hot and cause the bulb to burn out prematurely. Wearing gloves can prevent this transfer of oil.
The enemy of a rusty bolt is?
Rusty bolts are the bane of a mechanic's existence, but they are not impossible to work with. Most shops keep a torch handy to heat up these bolts and break down the seemingly impossible bond the rust has created. After heating the bolt, it should come out under normal pressure.
Can you easily adjust every vehicle’s camber, caster and toe?
Almost every vehicle has quick toe adjustment, but camber and caster may require special bolts or shims to get right. Most parts stores stock these items. In some cases, the only way to fix severe issues is with new parts.
How do you compress the piston in most rear calipers?
Most rear calipers use a screw-style piston to activate the parking brake. This piston requires a delicate combination of clockwise rotation and inward pressure to compress it. The only way to effectively do this is with a special rear-caliper tool. Many auto parts stores rent these tools to DIYers.
A customer complains about a mild drift to the right, does his car likely need an alignment?
Most major roadways have a peak in the middle and mild slopes downward on the edges. This can cause a car to drift slowly to the right. It is still a great idea to check his alignment, but make sure to set this expectation of the mild drift.
Will an alignment issue cause a vibration?
While an alignment can technically cause a vibration in some instances, these are very rare occurrences. Vibrations typically stem from tire or braking issues. It's always worthwhile to check the alignment, but you will also want to check the tires and brakes.
In the mid-1990s and early-2000s, Chrysler was famous for hiding car batteries where?
In its midsize sedans from the mid-1990s through the early-2000s, Chrysler saved room under the hood by putting the battery in the wheel well. To access the battery, you had to turn the wheel to one side and peel back the wheel-well cover.
What is the correct brake-bleeding sequence?
Each model's brake system is different, so their brake hoses route in different ways. This means each model of vehicle will have a different brake-bleeding procedure. You must do this in the right sequence or risk reintroducing air into the brake system.
You’ve got a car throwing an “EVAP Leak” code. What is the first thing you check?
An "EVAP" code means there is a vacuum leak in the evaporative emissions system, and the fuel tank is part of this system. Oftentimes, drivers will refill their fuel tank and forget to tighten the cap, which may trigger a check engine light with an "EVAP" diagnostic code. This does not mean this code always points toward a fuel cap, but it is the best place to start.
With any electrical problem in a vehicle, what is the first thing you check?
Blown fuses and relay sometimes cause the most frustration for any tech chasing down what appears to be a mystery electrical issue. Starting at the fuse and relay block can eliminate the frustration of finding out you spent three hours chasing an issue that ended up being just a blown fuse or faulty relay.
A car is overheating, and the upper radiator hose is significantly cooler than the lower hose. What’s the likely issue?
If the thermostat fails and does not let the coolant flow back into the radiator, the engine will overheat but the upper radiator hose will remain dramatically cooler than the lower hose because no coolant will flow through it.
A customer asks for a free diagnostic scan, and you turn up a “random misfire” code. What is your next step?
A free diagnostic is purely to give you an idea of where to start, and a "Random Misfire" code can lead you down several paths. The safest bet is to get a per-hour diagnostic approval so you can find the source of the problem and fix it the right way.
Some performance vehicles -- particularly German ones -- require this to perform an alignment.
Many performance cars, especially German ones, have their suspensions tuned for carrying passengers and still delivering top-notch performance. This means an alignment technician must simulate the weight of the passengers and driver in the car. They do this using special sand bags.
What other components should you always replace when doing a timing belt?
The timing belt is one of the most sensitive and expensive belts in your vehicle. While replacing it, it is best practice to also replace all the timing belt pulleys, tensioners and the water pump. This helps prevent other problems in the area from damaging the expensive repair you just did.
A customer brings in already-balanced aftermarket wheels and tires for you to install. What do you need to add to prevent vibrations?
Every manufacturer's hubs are different diameters, and installing wheels directly onto these hubs can cause vibrations. Hub centric rings sit inside the hub of the aftermarket wheels and fit snugly over the manufacturer's hub, preventing vibrations.
Is a tire plug a reliable repair method?
Plugs are great for quick on-the-road repairs, but they are not a permanent solution. The only permanent repair for a punctured tire is an internal patch bonded to the tire itself.
A car’s A/C is blowing warm, and you find it is low on refrigerant. Will refilling the system fix the problem?
A/C systems should never leak refrigerant, as they are sealed systems. If the refrigerant level is low, there is a leak somewhere and refilling a leaking A/C system is actually a violation of federal law.
What are torque sticks?
Torque sticks attach to an impact gun like any other socket. The socket is at the end of a long, thin stem that varies in size to help limit the amount of torque transfer from the gun to the lug nut. This allows mechanics to quickly reinstall wheels without worrying about overtightening them.
What is a telltale sign of underinflated tires?
Underinflated tires tend to sag in the center, putting all the weight on the outer edges of the tires. This causes excessive wear on the outer edges of the tread.
A timing belt broke, is the engine toast?
Timing belts in interference engines -- those with very tight tolerances -- can cause valve damage if they break during operation. That said, a broken timing belt is not a death sentence. A full inspection may prove there was no valve damage.
What is the typical cause for vibration while braking?
While people are quick to say, "My rotors are warped," they fail to realize just how hard it is to actually warp them. Typically, vibration when braking is from brake pad material transferring from the pad to the rotor due to high heat. A quick rotor resurfacing generally fixes the issue.
What is a non-serviceable rotor?
Non-serviceable rotors are ones you cannot resurface on a brake lathe. Whether it's because the rotors are manufactured within tighter tolerances or just made of a metal that cannot be resurfaced, you have to replace them every time you replace the pads. You'll typically find these on performance and foreign cars.
Automotive knowledge is earned, not given. You earn it through countless years of getting grease under your fingernails, banging your knuckles off sharp metal and hammering off rusted bolts while sticking your arm in spaces it really shouldn't fit. This is the life of an automotive mechanic, and there is no way to fake this type of experience.
Automotive knowledge includes things like basic history and understanding the difference between horsepower and torque, but there is a whole other side of cars that is foreign to many car lovers. I'm talking about the mechanical side of them, like how the engine actually creates its power, how the air conditioner cools a vehicle and why coolant is always such a bright color. These are all questions automotive mechanics should be able to answer in their sleep.
Any gearhead or car junkie can call themselves an automotive expert, but a true car expert understands the mechanics of the vehicles they love so much. Do you think you have the automotive knowledge of an auto mechanic? Give this test a shot to see how much you know about auto mechanics and the inner workings of cars.
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