Professional auto technicians use their sense of smell, touch, sight and hearing all the time to help diagnose vehicle problems. With a little knowledge and practice you can as well. In this article series, “Use Your Senses to Diagnose Vehicle Problems”, we’ll explain how to use each one of your senses as a diagnostic tool. Let’s start with the sense of smell.

Sense of Touch

For centuries, humans have been interacting with machines. Our sense of touch has enabled us to create and manipulate all sorts of devices; marvelous inventions that we’ve designed to make our lives easier, fun and more efficient. The vehicles we drive everyday are perfect examples. But what do we do when they break down?

In the automotive world, we can diagnose many problems with our sense of touch. An unusually rough ride, difficult handling, vibrations, odd temperatures and poor engine performance are tangible symptoms that can be felt. They almost always indicate some type of problem. In this article, we’ll focus on how to use your sense of touch as a diagnostic tool.

Control and Vibrations

Steering and Control – If your vehicle’s steering feels vague or is hard to hold in a straight line on the freeway, it may be something as basic as under-inflated tires or something more serious like your front wheels are misaligned, and/or you have worn out steering components. The most common components to cause steering issues are tie rods, control arm bushings, tension rod bushings, ball joints or steering rack bushings.

Ride and Handling – Worn struts or shock absorbers and other suspension components can contribute to a rough ride and poor cornering characteristics. Original equipment shocks and struts usually maintain optimum performance for about 20,000 miles, depending on the type of roads you drive on. An easy way to determine if your shocks or struts are worn out, is to bounce your vehicle up and down hard at each wheel and then let go. How many times does the vehicle bounce? Weak shocks or struts will allow the vehicle to bounce twice or more. Your vehicle’s springs usually do not need replacement unless one corner of the vehicle is sagging lower than the others.

Vibrations – When you drive at speeds between 50 and 70 miles per hour on a smooth road, does your steering wheel shake or do you feel a vibration in your seat? Unbalanced or improperly balanced tires are the most common cause of these types of vibrations. If you feel vibrations in the steering wheel, that’s typically caused by problems with the front tires. Vibrations in your seat are usually caused by rear tire issues. In some cases, worn out front or rear suspension components can cause vibrations. Also, worn out driveline U-joints or an unbalanced driveline can cause vibration in the seat.

A damaged front tire can cause a shimmy in the steering wheel, especially at speeds below 35 miles per hour. Hitting a curb or pothole can cause belt separation and damage.

Address vibrations as soon as possible to avoid premature wear on steering and suspension components.

Brake Vibrations – Vibrations when braking is almost always caused by warped brake rotors. You may feel the brake pedal pulse under your foot during high-speed braking if either front or rear brake rotors/drums are warped. To better pinpoint which brakes are the problem, pay attention to what else is vibrating. If you feel the vibration in the steering wheel, the problem is with the front brake rotors; if you feel vibrations in your seat, the problem is with the rear brake rotors/drums. Braking efficiency is compromised when the brake rotors or drums are warped so replace the rotors or drums or have them machined as soon as possible.

If the vehicle pulls to the right or left when the brakes are applied, look for a sticking brake caliper on only one side. In these cases, the set of brake pads doing the stopping is excessively worn out. If the brake pedal sinks to the floor while maintaining constant pressure, an internally leaking brake master cylinder is the most common cause.

Do you feel and hear scraping or grinding during braking, especially at low speeds? If so, your vehicle’s brake pads are completely worn out and the metal brake pad backings are now contacting the brake rotors. You can usually look through the wheels and see your brake rotors. If they are deeply grooved and discolored, plan on replacing the brake pads and rotors. Because this situation creates a lot of heat, it’s best to rebuild or replace the brake calipers and replace the brake fluid.

Incorrect or Odd Temperatures

Cooling System Issues – When the engine is fully warmed up and the cooling system is operating correctly, the top radiator hose should be hotter than the bottom hose. The upper portion of the radiator core should also be warmer at the top and cooler at the bottom.

Radiator – Feeling radiator core temperatures can be used to diagnose cooling system issues. Once the engine is warmed up completely, shut it off and CAREFULLY feel the radiator core for hot and cold spots. You can also use a digital inferred thermometer.

• If the radiator is hot on the bottom and not on top, air may be air trapped in the system that will need to be bled out.
• If the radiator core has cool spots in various areas, it’s partially clogged.
• A typical plugged radiator core symptom is when the engine temperature is normal on the freeway or with an electrical radiator fan running but runs hot in stop-and-go traffic.
• In some cases, a transmission or power steering cooler mounted too close to the front of the radiator can cause overheating issues.
• Many vehicles use separate internal tubes in the radiator to help cool the automatic transmission. Sometimes an overheating transmission can cause higher engine temperatures because the radiator can’t cool both efficiently.
• Radiator fins that are plugged with dirt and debris can restrict air flow resulting in engine overheating issues. Clean radiator fins by spraying water through them from the backside.

  CAUTION: Do not use a pressure washer. You can also use a soft brush to remove debris from the fins.

Radiator Hoses – With the engine warmed up, feel the upper radiator hose.

• If the upper radiator hose is cold, the thermostat is likely stuck closed.

• If the upper radiator hose gets hot before the engine has properly warmed up, it means the thermostat is not closing correctly or is stuck open.
• In some cases, a cold upper radiator hose is due to poor coolant circulation, which can be caused by a restricted radiator or a water pump with broken or worn off impeller fins.
• If the upper radiator hose is collapsed after the engine has cooled down, a stuck radiator cap is likely the culprit. To fix it, replace the cap with the correct pressure rating.

  CAUTION: Do not remove the radiator cap or overflow bottle cap when the engine is hot. Doing so may results in severe burns.

Heater Core and Hot Water Valve – During normal heater operation, you can feel that both heater hoses going through the firewall are hot. It’s normal for the heater hose coming out of the vehicle to be a little cooler than the hose going in.

But, if the heater hose coming out of the vehicle feels a lot cooler than the heater hose going in, and the heater doesn’t feel very hot, look for a restricted heater core or a malfunctioning hot water valve.

Air Conditioning (A/C) System – Use your sense of touch to diagnose problems with you’re A/C system. Set the blower fan speed to a medium or high and select the vents you want the A/C to come through (defrost, dash vents, foot vents).

• Put you hand in front of the selected vents to verify air is exiting through those vents.
• With the A/C on, you should feel very cold air exiting the vents. If it’s warm or just cool, you’re A/C system likely has a refrigerant leak, blend door issue or A/C component malfunction.
• When the A/C is operating normally, the big low-pressure line at the A/C compressor will feel cold, the small high-pressure line will feel hot.

Hot Electrical Components – No electrical component or wire should ever feel hot to the touch. If they do, an excessive circuit load or resistance is likely.

Lack of Engine Performance

Lack of power can happen suddenly, which is easy to detect, or it can decrease gradually, which is more difficult to notice. Gradual loss of power is most common. Here’s an example. Say six months ago, your car was able to zip up a particular hill with little effort. You barely had to press the gas pedal down. But over the last month or so you’ve noticed that you had to press the gas pedal down further and the automatic transmission is downshifting more often to get up the same hill. You may have also noticed that it takes longer to get up to speed when merging onto the freeway. These are signs you’ve lost engine performance.

Items like a restricted air or fuel filters, dirty fuel injectors, weak fuel pump or a malfunctioning fuel pressure regulator are the most common reasons for gradual loss of power.

Sudden loss of power, on the other hand, may be caused by a defective mass air flow (MAF) sensor, manifold absolute pressure (MAP) sensor or an engine misfire. Problems with fuel injection system components will typically cause the malfunction indicator light (MIL) in the dash to come on. You may notice a lack of power just before that happens.

Other problems like a slipping transmission or clutch, dragging brakes or excess weight in the vehicle can cause power loss without triggering the MIL. Whatever the reason is for a lack of power, it’s best to fix problem as soon as you notice it. The longer you wait, the more it could cost to fix.

Use Your Senses to Diagnose Vehicle Problems
What's That Smell? | Looks Like Trouble | Did You Hear That?