Pre-Purchase Inspection On A Used Car: Uncover Hidden Issues

The Importance of Getting A Pre-Purchase Inspection On A  Used Cars

Unlike new cars, used vehicles come with a history, which may include accidents, mechanical issues, or hidden defects that aren’t immediately apparent during a casual test drive. This is where a pre-purchase inspection on a used car becomes invaluable. In this article, we’ll explore why a PPI is essential when buying a used car, what it involves, and how it can save you from potential headaches and financial losses down the road.

Even if you’ve been buying cars your whole life, you can’t check everything about a used car while it’s sitting in someone’s driveway. It needs to be up on a lift, and it needs to be checked with a professional-grade scan tool to make sure the seller hasn’t recently erased trouble codes, codes that will pop up again right after you buy the car.

A Pre-Purchase Inspection On A Used Car Uncovers Hidden Issues You Can’t Find At The Car Lot Or in The Seller’s Driveway

One of the primary reasons for conducting a PPI is to uncover hidden issues that aren’t immediately visible. Even if a car looks immaculate on the outside and drives well during a test drive, there could be underlying problems that only a trained eye can detect. These issues might include:

• Engine Problems— A mechanic can check for signs of wear or impending failure in the engine, such as oil leaks, unusual noises, or irregular emissions.

• Transmission Issues— Problems with the transmission, like slipping gears or delayed shifting, may not be obvious to a non-expert during a short drive.

• Suspension and Brakes— The suspension and brakes are critical for safety. A PPI will reveal if these components are in good working order or if they need expensive repairs.

• Electrical Systems— Modern cars are full of electronics, from the infotainment system to critical safety features like airbags and anti-lock brakes. A PPI ensures that all electrical components are functioning properly.

• Frame Damage— A vehicle with frame damage from a previous accident may not be safe to drive, and such damage can be expensive to repair. Inspectors can identify signs of previous repairs or structural issues.

When and How to Get a Pre-Purchase Inspection

Ideally, a PPI should be conducted after you’ve selected a used car that you’re seriously considering but before finalizing the purchase. Most sellers, whether private individuals or dealerships, will agree to a PPI if you request one. It’s a reasonable request, and any seller who refuses should raise a red flag.

To arrange a PPI, you can either take the car to a trusted mechanic or hire a mobile mechanic who can come to the location of the vehicle. Ensure that the mechanic performing the inspection is experienced and reputable.

Here’s what a shop normally checks during a pre-purchase car inspection

1) Stationary scan tool review— With the car parked, ignition on, but engine off

Readiness monitors

Any time trouble codes are erased, the vehicle computer must complete a “drive cycle” to test that system and make sure it passes. If that system passes the tests, a “readiness monitor” will show that the system is “ready.” However, if the seller recently cleared a trouble code but didn’t conduct the drive cycle, the readiness monitor will show “not ready.” That’s a dead giveaway that the seller has been trying to trick you by clearing the trouble codes.

History codes

Many computers keep track of trouble codes that have been set in the past. Checking the history codes is a great way to see which codes have been set but are not “current” codes.

Pending codes

If a sensor is seeing bad data, but the data hasn’t exceeded the threshold to turn on the check engine light or the data has exceeded the threshold but the test requires the data to fail a set number of times before turning on the check engine light, the computer will store the trouble code as a “pending code.” That’s the sign that you’re about to have a check engine light come on.

Mode $06 for misfires

Mode $06 is a way to peek behind the curtain to see exactly what data the vehicle computer is seeing. For example, by using Mode $06 you can see the number of misfires the computer is tracking for each cylinder, even though the total hasn’t reached the threshold to turn on the check engine light and set a trouble code. Mode $06 is a valuable tool in the hands of a skilled technician.

2) Test drive scan tool diagnostics

Short and long-term fuel trims

When a vehicle comes out of the factory, it runs on factory programming. As the engine wears, the computer makes changes to the factory programming to maintain proper operation while meeting emissions standards.

Short and long-term fuel trim readings tell the technician the general condition of the engine and what changes have been made to factory programming. Short-term fuel trim, for example, shows how much extra fuel the computer is adding to the factory programming to make the engine run properly. Once short-term fuel trim exceeds a certain value, the computer figures that it must continue to add that amount all the time and moves that data into the long-term fuel trim section.

Short—and long-term fuel trim data are expressed as a percentage above or below factory programming. So, a scan tool review that shows a long-term fuel trim of ±25% is a sign of a problem since short-term fuel trims should generally be less than +10%. What causes such a high fuel trim value? Vacuum leaks, clogged fuel injectors, low fuel pump pressure, and engine wear.

On the flip side, a negative fuel trim reading means that the engine is receiving too much fuel, and the computer is trying to cut back from factory programming. What causes negative fuel trim? Things like leaking fuel injectors or improper fuel pump pressure.

3) Pre and post O2 sensor operation

The scan tool can also be used to check the operation of the oxygen sensors and the catalytic converter.

4) Inspection of the AC system can determine the proper performance.

The technician installs pressure gauges and operates the AC to determine if high and low side pressures are within normal limits.

While the system is running, the tech checks the outlet temperature at the center duct to determine proper temperature drip.

5) Belt and belt tensioner inspection

Back in the ’80s and 90’s you could check the drive belt condition by checking for cracks in the ribs. By the late 1990s all car makers had switched away from neoprene belts and moved to EPDM belts that don’t crack. You can inspect an EPDM belt visually for tears and glazing, but you can’t detect wear visually. You must use a wear gauge to determine if the belt is worn. That’s what the tech will use during the pre-purchase inspection. They’ll also check the condition of the automatic belt tensioner to make sure the dampener components are working properly.

6) Timing belt Condition

The technician will remove a cover from the timing belt system and check for cracks, glazing, missing, or broken belt teeth.

7) Fluid checks

In addition to checking fluid levels, the technician will check for fluid condition of the coolant, power steering fluid, transmission fluid and brake fluid using test strips and a refractometer.

Brake fluid test strips check for the presence of copper in the fluid, which is an indication of the breakdown of the fluid’s anti-corrosion additives. A brake fluid moisture meter detects the presence of moisture in the system.

Coolant test strips detect improper pH balance, and a refractometer detects freeze protection and coolant/water concentration.

8) Tires

Tires should be checked for even tread depth across the tire and between all tires, tire damage, uneven wear, heat cracks, and age

9) Suspension checks

Shocks and strut condition

A test drive will determine strut and shock condition by checking for nosedive and rear squat during acceleration and vehicle stability in turns. A visual strut and shock inspection will detect leaks and mount condition.

Ball joints, control arm bushings, lateral links, stabilizer bushings and stabilizer bar end links

A visual inspection of all bushings and a test drive can determine the condition of most suspension components and the technician can also measure wear on the vehicle’s ball joints.

10) Steering checks

The technician will check inner and outer tie rods for wear as well as rack and pinion operation and intermediate link condition.

11) Leak check

The technician will check transmission and engine seals for evidence of leak, as well as a leaking rack and pinion, power steering pump and lines, transmission cooler lines, radiator and heater hoses, oil pan, valve cover leaks.

12) Brake check

The technician will remove the wheels to check for the remaining amount of friction material on the brakes and check for proper caliper and drum brake hardware operation. They’ll also check the friction material for signs of uneven wear and check the brake lines for signs of corrosion

13) Drivetrain components

Check CV axle shaft boots
Check drive shaft U-joints for wear
Chassis inspection
Check for signs of severe rust and previous repairs

14) Flood inspection

Check for signs of water damage from flood

15) Body panel inspection

Check for signs of previous body repair

16)Lights

Check all bulbs for proper operation

Test drive to check for proper shifting, wheel balance, and tire pull issues, handling in turns, proper engine temperature, and stopping ability.

What to do with the results of a pre-purchase inspection on a used car

If the pre-purchase inspection turns up serious issues like severe rust, major engine or transmission issues, or accessory failures that will cost a lot to fix, you should cancel the purchase and find a different vehicle. However, like buying a used house, a used car will most likely have some issues that need to be addressed. For example, you wouldn’t want to cancel the sale just because the pre-purchase inspection revealed that the brakes are worn. That’s a normal wear item that’s easily fixed.

However, if the pre-purchase inspection turns up multiple issues that require repair, get an estimate from the shop and re-negotiate the price of the used car

©, 2020 Rick Muscoplat