Buying a used car can be a great way to save money, but it also comes with a few risks — especially when it comes to the engine. You can polish the paint, replace the tyres, or clean the seats, but if the engine’s not in good shape, you could be buying a headache instead of a bargain.
So, before you hand over your hard-earned cash, it’s worth taking a few minutes (or hours) to check the engine’s health. You don’t need to be a qualified mechanic to spot the obvious warning signs — just a bit of patience, common sense, and this handy checklist.
1. Start with a Visual Inspection
Pop the bonnet and have a good look around. Even if you’re not a car expert, your eyes can tell you plenty.
Check for:
- Oil leaks or residue – If you spot fresh oil around the engine block or under the car, that’s not a good sign.
- Coolant leaks – Look for dried coolant stains (often green, pink, or orange) near the radiator or hoses.
- Corrosion or rust – Some surface rust is normal, but heavy corrosion on engine components can hint at neglect.
- Loose wires or hoses – These can indicate poor maintenance or dodgy repair work.
A well-kept engine bay usually means the owner has taken care of the car overall.
2. Check the Engine Oil
Pull out the dipstick (usually marked yellow), wipe it clean, dip it back in, and pull it out again.
You’re looking for:
- Oil level – It should be between the “min” and “max” marks. Low oil might mean poor maintenance.
- Oil colour – Clean oil is golden brown. Dark, dirty, or sludgy oil suggests it hasn’t been changed regularly.
- Metal flakes or grit – If you notice shiny bits on the dipstick, that’s a red flag. It could mean internal engine wear.
Pro tip: Ask the seller when the oil was last changed. If they’re vague or unsure, that’s another warning sign.
3. Look at the Coolant
Next up, check the coolant level and condition. The coolant reservoir is usually a translucent plastic tank near the radiator.
Healthy coolant should be bright in colour and free of oil or sludge. If it looks brown, thick, or has an oily film on top, it could mean the head gasket is leaking — a costly fix you don’t want.
4. Listen to the Engine Run
Start the car and let it idle. A healthy engine should start easily and settle into a smooth, steady rhythm.
Listen for:
- Knocking or tapping sounds – These could signal worn bearings or valve issues.
- Hissing – This might be a vacuum leak or cracked hose.
- Rattling – Could mean loose timing chains or components.
Also, give it a few light revs. The engine should respond smoothly without hesitation or strange noises.
5. Watch the Exhaust Smoke
Exhaust smoke can tell you a lot about what’s going on inside the engine.
- Blue smoke – Burning oil. This could mean worn piston rings or valve seals.
- White smoke – Could be coolant leaking into the cylinders (a sign of a blown head gasket).
- Black smoke – Too much fuel is being burned, possibly due to a fuel system issue.
A little puff on startup is okay, especially for older cars, but constant smoke is a no-go.
6. Check for Vibrations or Rough Idling
While the car’s idling, pay attention to how it feels. If the engine shakes excessively, misfires, or the revs keep fluctuating, it may be struggling with ignition, air intake, or fuel delivery issues.
Take it for a short drive if possible — a healthy engine should pull smoothly without jerks or loss of power.
7. Scan for Warning Lights
Modern cars make life easier with dashboard warning lights. If you see the Check Engine, Oil Pressure, or Temperature light glowing, don’t ignore it.
You can even use a simple OBD2 scanner (available for under $50 online) to read any error codes. This can reveal issues the seller might not mention — or even know about.
8. Check Service Records
A car’s service history can tell you almost everything about how well it’s been looked after. Regular oil changes, timing belt replacements, and cooling system checks are great signs.
If the logbook shows gaps or “DIY” repairs with no receipts, it’s best to be cautious. In Australia, most reputable sellers or dealerships will provide full service records — if they don’t, ask why.
9. Get a Pre-Purchase Inspection
If you’re unsure or don’t feel confident doing these checks yourself, hire a licensed mechanic for a pre-purchase inspection.
In Australia, mobile mechanics can come to the seller’s location and check the car on the spot. They’ll give you a written report detailing any mechanical issues, which can save you from buying a lemon.
10. Don’t Rush the Decision
Finally, take your time. A used car is still a big investment, and there’s no rush to buy the first one you see. If something doesn’t feel right — the engine noise, the seller’s attitude, or the condition — trust your gut and walk away. There are plenty of good cars out there.
In Short
Checking a used car’s engine health isn’t just about poking around under the bonnet — it’s about paying attention to details. Look, listen, and ask questions. Whether you’re buying from a dealer or a private seller, a few simple checks can save you thousands down the line.
Because at the end of the day, a shiny car means nothing if the engine’s not happy — and neither will you be.
If you are in South Yarra, and looking for a cash for cars service, this is the best way to visit us.
Richmond Cash 4 Cars
(03) 7047 6388