1. Does your repair shop have ASE certified technicians working on customer's cars?
2. What is the difference between diagnostics and inspections?
3. What is diagnostics and why is it not waived if I approve the necessary repair?
4. What is the difference between OEM and After Market parts?
5. What is an O2 sensor and what does it do?
6. How long does an alignment last?
7. How often should the hoses and belts be replaced in my car?
8. How often should the engine antifreeze or coolant be flushed?
9. What is the difference between preventative maintenance and vehicle repairs?
10. What if my vehicle fails the Illinois Emission Test?
11. What kind of testing is done by the IEPA to check my vehicle's emissions?
12. What is the difference between the OBD test and the IM240 test?

1. Does your repair shop have ASE certified technicians working on customer's cars?

Rockdale Automotive has ASE certified technicians to repair any of your vehicle's needs.  Our technicians attend training at least twice a year to continually stay up-to-date on the latest trends and technology available to repair your vehicle.

2. What is the difference between diagnostics and inspections?

An inspection is a physical or visual check that does not require the use of sophisticated testing equipment.  Diagnostic testing requires the latest technological equipment and highly trained technicians with specific diagnostic experience.  Typically any repairs that use computer controls require diagnostic testing.

3. What is diagnostics and why is it not waived if I approve the necessary repair?

Diagnostic testing is used to determine the root cause of the vehicle's performance concern.  In order to ensure the best diagnosis, the mechanic must be highly trained and use state-of-the art testing equipment.  The labor time that the technician requires during the diagnostic process is mutually exclusive of the labor time required to actually fix the problem.

4. What is the difference between OEM and After Market parts?

OEM stands for "Original Equipment Manufacturers".  OEM parts are the exact same parts that are supplied to the manufacturer during fabrication of the car.  After market parts are made by companies other than OEM.  Some after market parts can be better than OEM parts.  The after market parts meet or exceed the OEM design and usually carry a longer warranty period.  Rockdale Automotive only uses OEM or after market parts that meet or exceed the manufacturers specifications.

5. What is an O2 sensor and what does it do?

An O2 sensor is short for oxygen sensor.  The purpose of the oxygen sensor is to provide an onboard analysis of the air and fuel mixture by measuring the amount of unburned oxygen in the exhaust.  Oxygen sensors that are not operating properly can cause drivability problems and will cause the check engine light to come on.  This can reduce your vehicles fuel economy by 10-15%.  The most common problem causing oxygen sensors to fail is contamination by lead, carbon or silicone that coats the sensor.  Contaminated sensors must be replaced.

6. How long does an alignment last?

To everyone's dismay, there is no specific answer to this question.  A vehicle's alignment requires mechanical adjustments to the steering and suspension.  Once adjusted, your vehicle will drive straight.  Steering and suspension become 'out of alignment' due to road hazards such as curbs and potholes.  The harsher the road conditions, the more often the alignment will need to be readjusted.

7. How often should the hoses and belts be replaced in my car?

Each vehicle's manufacturer provides recommendations outlined in the vehicle's owners manual.  You should have your belts and hoses checked by a certified technician each time you have an oil change and the typical lifespan of belts and hoses are around 30,000 to 40,000 miles.  You should particularly have your belts and hoses checked before summer and winter.

8. How often should the engine antifreeze or coolant be flushed?

Once again, the vehicle manufacturer will provide you with recommendations outlined in the owner's manual.  Typically, the cooling system should be flushed at least once every two years or 30,000 miles.  A cooling system flush should never be performed to repair an overheating problem.

9. What is the difference between preventative maintenance and vehicle repairs?

When your car stops performing properly, and something is broken, you need to take your vehicle in for repairs.  The technicians will diagnose your vehicle to determine the problem and will suggest a repair strategy.  Most often, vehicle repairs are not expected.  Your car may not start, or your car may be running at a high temperature.  Repairs MUST be completed to get your car back on the road.

Vehicle maintenance is performed on your vehicle to keep it in the best possible running order.  Maintenance work is suggested at certain mileage intervals by the manufacturer to ensure that the vehicle continues to run properly.  If you neglect the maintenance schedule, your vehicle will require repairs because it will stop running properly.  Performing scheduled maintenance will not prevent your vehicle from breaking down, but it will keep the costs of repairs down and will let you get more miles out of your car.

10. What if my vehicle fails the Illinois Emission Test?

If your vehicle fails the IM240 Emission test, our highly skilled IM240 technicians can repair your vehicle.  Call us to schedule an appointment and bring the paperwork from the testing facility and we can perform our emission diagnostic service.  Our service includes:



• On-board computer analysis
• Analysis of primary and secondary ignition systems
• Fuel delivery system analysis
• Drive trace evaluation
• Cylinder balance test
• EGR system evaluation
• Data stream analysis
• Exhaust Gas analysis


This testing takes approximately 2 hours to complete and will determine what repair your vehicle needs.  Once we have discussed the options for repair with you, we will do the necessary work and bring your vehicle back to the test station for a retest.  If you have the work performed that we recommend, Rockdale Automotive guarantees that your vehicle will pass.

11. What kind of testing is done by the IEPA to check my vehicle's emissions?

Three types of tests are used.  In July 2002, an On-Board Diagnostic Test (OBD) replaced the traditional exhaust emissions test for most 1996 and newer passenger cars and light duty trucks (including vans and sports Utility vehicles.) An IM240 test is used for most 1981-1995 vehicles and a basic Idle test for 1968-1980 vehicles.

12. What is the difference between the OBD test and the IM240 test?

To simulate actual driving conditions, the IM240 test uses a treadmill device called a dynamometer.  The drive wheels are placed on the dynamometer while a hose collecting the vehicle's emissions is placed on the tailpipe.

Currently, OBD testing is being performed on most 1996 and newer vehicles.  Vehicles passing the OBD test will not receive the exhaust emissions (IM240) test.  Vehicles failing the OBD test will continue to receive the exhaust test, which will be used to determine compliance.  The test is designed especially for computer controlled vehicles, and it monitors emissions control systems for fault codes.  A connector, generally located under the driver's side dashboard, is used so the information can be downloaded from the vehicle's computer to the testing station's computer.  The codes are printed on the motorist's Vehicle Inspection Report to help automotive repair technicians diagnose emissions related problems.

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