How to Check a Used Car Part Before Buying

Last Updated: September 22, 2026

One of the smartest ways to keep a vehicle on the road without paying new-part prices is to purchase used car parts. But a second hand part is only a bargain if it fits, works and lasts. A cracked housing, incorrect revision or worn bearing can turn a bargain buy into an expensive return trip.

To summarise, when checking out a used car part before you buy, make sure it will fit your car’s build specifications and part number, check it for cracks, rust and heat damage, assess how worn it is and ask how it was tested. Before you pay, check the seller’s return policy. Experienced mechanics and parts interpreters use this step-by-step process. 

Step 1: Gather Your Vehicle Details First

Most wrong part buys occur before anyone touches the part. Have these ready before you call a wrecker or visit a yard:

• VIN (Vehicle Identification Number): Found on the compliance or build plate, windscreen area and your registration papers.
• Build date and model series – A Toyota Hilux from 2015 and 2016 may use different parts as there was a model change partway through the year.
• Engine and transmission codes: usually stamped on the engine block or in the build plate.
• Specification details: auto or manual, 2WD or 4WD, trim level and whether the car has options such as ABS, parking sensors or HID headlights.

A common pitfall is facelift models. Two cars can look almost identical, but use different headlight plugs, bumper mounts or sensor connectors. 

Step 2: Match the Part Number

The part number is the most reliable compatibility check you can do. Original equipment (OEM) numbers are typically stamped, cast or printed on a label on the part itself. When numbers are compared: Check the full number (with suffixes). One or two letters or digits at the end may indicate a revision with different internals or connectors.

• Know about supersessions. Manufacturers frequently replace an old number with a new one. A superseded part will usually fit, but check! Don’t assume it will fit.
• Understand the distinction between supplier and OEM numbers. An alternator may have a Denso or Bosch number as well as the car maker’s number. Match the car maker’s number when you can.
• Be careful of the electronic modules. Even if the part number is the same, ECUs, body control modules and some instrument clusters may need coding or immobiliser pairing to work in your car. Check with an auto electrician before you buy. 

Step 3: Inspect the Overall Condition

Look at the part as a whole before diving into the details. Is it flawless? Cost and time are added by missing brackets, sensors, pulleys or heat shields. Be sure the electrical connectors are not damaged or have any broken locking tabs or bent pins. Plastic connectors become brittle with age and Perth heat, and a cracked plug can cause intermittent faults which are very difficult to trace. And ask where the part was from. Knowing the donor vehicle’s make, model, year and rough kilometres tells you a lot more than a photo. 

Step 4: Check for Physical Damage

The main issues to be excluded are crash, heat and handling damage.

• Cracks: Check cast aluminium parts (gearbox housings, cylinder heads, intake manifolds) carefully, especially around mounting points. Wipe away the dirt. Oil and dust hide the hairline cracks.
• Mounting tabs and threads: Commonly found broken tabs on headlights and bumpers. A part with stripped or cross-threaded bolt holes can be unusable.
• Bent flanges and shafts: Even small bends in driveshafts, CV joints and suspension arms impact alignment and cause vibration.
• Heat damage: If any discolouration, melted plastic or scorched wiring is present around exhausts and turbos then the component has been over-heated.
• Flood damage: Warning signs are silt in crevices, white or green corrosion on terminals, or a visible tide line, particularly on electrical parts. 

Step 5: Assess Rust and Corrosion

Not all rust is a deal breaker. Knowing the difference keeps you from walking away from a good part or buying a bad one.

• Surface rust: A light orange film on cast-iron brake discs or steel brackets is normal for a part that has been sitting. Usually it wipes off.
• Scale rust: If rust is flaking and forming layers, metal is being lost. Use with care on suspension or structural parts.
• Perforation: If you see holes or crumbling metal, that part is done.

Inspect seams, spot welds and lower edges on doors and tailgates where water collects. Salt air in coastal suburbs may result in greater corrosion on cars so check under panels, not just the painted face. 

Step 6: Measure Wear

The biggest difference in used auto parts is wear, and a little knowledge pays.

• Brake discs: the minimum thickness is usually stamped on the disc. A pronounced lip on the outer edge is a sign of heavy wear.
• Suspension parts – inspect for cracked or perished rubber bushes and split ball joint or CV boots. If grease is flying around a CV joint, the boot has failed and grit may have got in.
• Rotating parts: Manually spin the alternator, power steering and air conditioning compressor pulleys. They should turn smoothly and quietly, without grinding or discernible play.
• Turbochargers – Check shaft for excessive in and out or side to side movement. Check for oil in intake side.
• Headlights: yellowed or fogged lenses, and water in the housing, reduce light output and may affect roadworthiness. 

Step 7: Confirm Functionality

A visual check doesn’t get you far. Ask the seller if and how the part was tested. Ask for compression readings or a video of the engine running before removal. For engines, ask. Pull the dipstick, if you see milky oil it could be a sign of head gasket failure. Burned smelling oil or heavy metal particles on the magnetic drain plug are warning signs for gearboxes. Many electrical parts such as window motors, fans and starter motors can be bench tested with a 12V supply. For major items, our guide about whether used engines are a good idea or not discusses more about the benefits and risks. 

Red Flags to Watch For

If you see any of the following, walk away or ask more questions:

• Part numbers ground off, painted over or labels missing
• A seller who doesn’t know what vehicle the part is from
• A freshly power-washed engine or gearbox – can hide oil leaks
• Fresh paint, filler or overspray on panels showing previous repairs
• Gasketed joints with silicone smeared around them
• Mismatched or missing screws
• Same part for much less than market price
• Refusal to give photos, part numbers or return terms. 

Buyer Checklist for Used Car Parts

Before you pay, check them off:

•  VIN, build date, engine and transmission codes verified
•  Part number matched with suffix
•  Donor vehicle model, year and mileage known
•  Partly finished, brackets, sensors and connectors in place
•  No cracks, bent areas, stripped threads or heat damage 
•  Rust only on the surface 
•  Wear within acceptable limits
•  Agreed-upon testing method with seller
•  Read and understood return and exchange policies 
•  Saved receipt 

Buying Used Car Parts in Perth: Be Upfront About the Terms

Used parts are used parts, period. Good sellers spell out their terms. For example, WA Auto Parts has a refunds and returns policy which states that parts are sold as second hand and that returns are handled on faults under certain conditions, with change of mind and incorrect orders not being covered. That’s why it’s so important to check compatibility before you buy. Keep your receipt always. WA Auto Parts is a Welshpool-based wrecker that dismantles all types of vehicles, from everyday sedans to utes and 4WDs. You can check out the brands covered on the brands page including Toyota, 4×4 and 4WD vehicles. To learn more about why wreckers are a great place to source quality used car parts, visit the benefits of buying used car parts from auto wreckers. 

Frequently Asked Questions

Are junkyard car parts any good?

If they are the right ones for your car and are properly checked they can be very reliable. A lot of OEM parts from lower mileage donor cars have a lot of life left in them. The key is checking condition and wear, and knowing the return policy of the seller.

How do I know if a used car part will fit my car?

Match the OEM part number then confirm your VIN, build date, engine code and spec. When you enquire, give these details to the seller to greatly reduce the risk of ordering the wrong part.

Surface rust on brake discs – is this a problem?

Discs that have been sitting around will often have a light surface rust, which will usually disappear after a few stops. If the disc has deep pitting, a heavy outer lip or thickness below the stamped minimum, it should be replaced.

Which second hand parts to avoid?

Many mechanics will recommend buying new consumables , such as brake pads , filters , timing belts , spark plugs and rubber hoses . Air bags and other safety-critical items require special care and professional advice.

Can I return a used part if it doesn’t fit?

That depends on the seller. WA Auto Parts returns policy does not cover wrong orders or change of mind purchases so make sure you check compatibility before you buy. Bad parts? See the full policy for details. 

Find the Right Used Car Part, the First Time

Have your VIN, build date and the part number handy then send a parts enquiry to WA Auto Parts or call (08) 9358 1392. Ask the team for donor vehicle details, condition and availability before purchase. You can also visit the yard at 103 Sheffield Rd, Welshpool (Mon to Fri 7.30am – 4.30pm, Sat 7.30am – 2.00pm) or get in touch online. We can make arrangements for postage of used parts depending on your location.