Buying a used car can be a smart financial move—but only if you know exactly what you’re getting. One of the most important (yet often overlooked) checks is whether the engine is original or has been replaced. At Double Chex, we inspect vehicles across Sydney and surrounding areas, and we know the signs to look for when an engine swap has occurred.
Here’s a simple guide to help you identify if your car’s engine is still the one it left the factory with—or if it’s had a heart transplant.
1. Check the Engine Number Against the PPSR Register
Every engine has a unique number. You can find this stamped on the engine block (location varies by manufacturer). Once located, run a PPSR (Personal Property Securities Register) check.
This report will show if the engine number matches the original registration details. A mismatch could indicate the engine has been swapped—or worse, that the car has been written off, stolen, or rebuilt.
2. Compare the Engine Number to the Vehicle Logbook
A new car’s service logbook often lists the original engine number. Cross-reference it with what’s currently in the vehicle. If the numbers don’t match and there’s no documentation of an official engine replacement, it’s worth digging deeper.
3. Inspect for ‘Witness Marks’ on the Subframe and Fittings
Trained eyes can spot signs of mechanical work. Look for:
Tool marks on bolts and brackets
Scratches or scuffs near engine mounts
Fresh sealant or gaskets that seem newer than the rest of the engine bay
These ‘witness marks’ suggest the engine has been removed and reinstalled.
4. Is the Engine Too Clean? It Might Be Too Good to Be True
If the engine bay looks immaculate, especially compared to the rest of the car, it may have been swapped or detailed to hide something. Most engines in used cars show signs of wear—some grime, dust, and oil residue is normal.
An engine that looks fresh off the factory floor in a 10-year-old car? That’s a red flag.
5. Look for Paint Texture Markings from Wreckers or Used Parts Suppliers
Motor vehicle recyclers often use specific paint pens or texture marks to label parts. These could include:
Colour-coded paint dabs
Numbers written on major components
Stickers with yard codes
If you spot any of these markings, it’s likely the engine (or parts of it) came from a wrecking yard.
6. Inspect Electrical Plugs and Wiring Looms
Wiring looms are rarely touched unless the engine has been out. Look for:
Clips that don’t match others in the bay
Broken or brittle connector tabs
Non-original tape or heat shrink
Tags or stickers on the wiring
These signs may suggest the loom has been removed, re-routed, or replaced.
7. Check the Full Service History
This is your most important piece of evidence. A complete, well-documented service history will usually note any engine replacements, repairs, or rebuilds. Look for:
Consistent servicing by a dealership or licensed mechanic
Invoices for engine-related repairs
Notes or records of an engine swap
If the service history is patchy—or missing entirely—proceed with caution.
Final Thoughts: Trust the Experts
Determining whether an engine has been replaced isn’t always straightforward. That’s why it pays to get a professional pre-purchase car inspection from a team that knows what to look for.
At Double Chex, we offer mobile car inspections across Sydney, and we check every vehicle as if it were our own. From engine number checks to structural integrity and service history verification—we’ve got you covered.
Need peace of mind before buying your next car?
Book a pre-purchase car inspection with Double Chex today.