Buying a used car can be a smart decision – you save money, get a decent vehicle, and avoid the heavy depreciation that new cars face. But there is a problem- engine condition. Most buyers only check the body condition or interior, but engine inspection is the most important part. A well-maintained engine means peace of mind, but a repaired or tampered engine can cause endless trouble later.
In this blog, we’ll explain how to identify if a used car’s engine has been repaired, what signs to look for, and how to protect yourself before making a deal.
1. Visual Clues That Indicate Engine Repair
The first step in engine checking is visual inspection. You don’t need to be a trained mechanic – just a little observation. Let’s see what you should look for.
A. Fresh Paint or Mismatched Color
If you open the bonnet and see that some parts of the engine have fresh paint or a color different from the rest, it can be a clue. Manufacturers paint engines in a single uniform tone, but after a repair, local garages sometimes repaint a section to hide scratches or welding marks.
| Visual Clue | Possible Reason |
| Fresh black or silver paint on the engine block | The engine head or block may have been opened or replaced |
| Uneven paint or rough texture | Local repaint after repair |
| New-looking bolts or seals | Recent opening or part change |
B. New Sealant or Gasket Lines
Engine gaskets & sealants are used to keep fluids in place. If you see fresh sealant (silicone-type glue) around the cylinder head or oil pan, that means the engine has been opened recently. Factory sealants are clean and uniform, while repaired ones look thick, uneven, or messy.
C. Bolt Marks or Scratches
Factory-fitted bolts are machine-tightened – they look neat and untouched. But after a repair, bolts often have spanner marks or scratches. Check carefully around cylinder head bolts, manifold joints, and engine mounts.
D. Welding or Non-factory Joints
Where you see welding marks or non-factory joints, it’s a red flag. It may indicate crack repair or replacement of the engine block, which is a major repair.
2. Unusual Engine Sounds or Vibrations
For an experienced driver, the sound of the engine tells everything. A repaired or unhealthy engine often produces abnormal sounds or vibrations, even if everything looks fine from the outside.
A. Knocking or Tapping Sound
A knocking sound (tak-tak or knock-knock) usually means some problem inside the engine – maybe the connecting rod bearings or piston rings have been replaced or fitted incorrectly. This is a strong hint that engine work has been done.
B. Hissing or Whistling Noise
If you hear hissing when the engine is running, it could be due to a vacuum leak or loose hose – sometimes caused by improper reassembly after repair.
C. Rough Idling or Vibration
When the car is at idle (neutral gear, engine running) and vibration is being felt in the steering or body, there could be an engine mount or balancing issue. Engine mounts are often removed or replaced during major engine work.
D. Smoke Color Check
Observe the exhaust smoke:
- Blue smoke → Oil burning (possible piston or valve issue)
- White smoke → Coolant leak (head gasket repair issue)
- Black smoke → Rich fuel mixture (engine tuning problem)
These are clear indications that something inside the engine has been repaired or is malfunctioning.
3. Checking for Oil Leaks and Fluid Condition
Engine oil and fluids are like the blood of a car – everything runs through them. Let’s see how to check properly.
A. Engine Oil Condition
- Pull out the dipstick, wipe it clean, and insert it again.
- If the oil is very black or gives a burnt smell, it means poor maintenance.
- Milky or foamy oil indicates coolant mixing – could mean head gasket repaired or damaged.
B. Oil Leaks
Look around:
If you notice leakage near the oil pan, valve cover, head gasket area, and timing cover, it’s a concern.
Fresh oil marks or wet areas show a recent leak, maybe after improper fitting.
| Area to Inspect | What It Indicates |
| Around the head gasket | Recent repair or engine opening |
| Near the oil filter housing | Poor installation |
| Under the car (oil pan) | Crack or loose bolts after engine work |
C. Coolant and Other Fluids
Coolant color is green, red, or blue – if brownish, it means oil mixing, which happens after gasket repair or overheating.
Also, check brake fluid and power steering fluid – any contamination or leak is not normal.
4. Inspecting Service Records and Engine History
Paperwork never hesitated. Even if the seller tries to hide, service records reveal everything.
A. Authorized Service Center Records
If the car has been serviced at an authorized centre, ask for the service history printout. You’ll see all repair entries there – including engine overhaul, gasket replacement, or piston work.
B. Independent Garage Invoices
If there are no authorized records, ask for local garage bills. Genuine owners will share maintenance bills; doubtful sellers will avoid.
C. Engine Number Verification
Each engine has a unique number. Compare it with the number on the RC book and chassis plate.
If they don’t match, it means the engine has been replaced – a major repair case.
| Document | What to Check | What It Means |
| Service Book | Engine overhaul entry | The engine was opened/repaired |
| RC Book | Engine number | Mismatch means engine change |
| Warranty Papers | Expired or void | Major repair done |
D. Ask About Ownership and Usage
If the car was used for taxi, ride-share, or long-distance runs, engine repair chances are high. Such cars usually have higher engine wear.
5. Using an OBD Scanner for Hidden Engine Issues
Modern cars come with an On-Board Diagnostics (OBD) system that stores all engine-related error codes. This is a smart way to detect hidden problems that you can’t see manually.
A. What is an OBD Scanner?
It’s a small device that connects to the car’s OBD port (usually below the steering). It reads all error codes stored in the ECU (Engine Control Unit).
B. What You Can Detect
- Misfire codes (P0300–P0306)
- Sensor issues (oxygen, crankshaft, camshaft)
- Fuel mixture or timing issues
- Previous repair-related errors were not erased properly
If no “Check Engine Light” is still on, the OBD scanner can still show pending or historical codes – proof that engine work was done recently.
C. Example Table – Common OBD Codes
| Code | Problem | Possible Cause |
| P0300 | Random Misfire | Faulty spark plug, piston issue |
| P0420 | Catalyst Efficiency Low | Exhaust or sensor issue after repair |
| P0171 | System Too Lean | Air leak or wrong tuning |
| P0117 | Coolant Temp Sensor Low | Wiring issue after gasket repair |
You can even ask your local mechanic or a GoMechanic workshop to run this scan before finalizing the deal. It hardly takes 10–15 minutes and gives a full picture of engine health.
Conclusion
Buying a used car can be a smart choice, but only if you understand the condition of the engine well. The engine is the heart of a car – if it’s in good condition, the car will run problem-free for a long time. But if the engine has been repaired and you don’t know about it, then servicing, oil leakage, vibration & performance issues start to arise later. So, when looking at the car, always do a visual inspection of the engine, check the oil and coolant & take a short test drive to get a feel for the sounds & vibrations. Check the service records and OBD scanner report; these all provide proof whether the engine is genuine or repaired. If you have even the slightest doubt, have it inspected by an expert mechanic – this simple step can save you a significant expense. Ultimately, the best decision when buying a used car is when you can confidently say the engine is in perfect condition.
FAQ’s
1. How do you check if an engine has been replaced?
First, check the car’s service record or invoice – it will indicate if the engine has been replaced. Match the engine number to the RC book and chassis number. If the number is different or the bolts appear to be new, understand that the engine has been replaced. Also, have a mechanic confirm this.
2. How to check if a used engine is good?
Listen for any odd noises, such as tapping or knocking, as soon as you start the engine. The exhaust should not produce any blue or white smoke. Verify the oil’s colour & level; it shouldn’t be dark or milky. Feel the pickup and fluidity on a test drive.
3. How to check if an engine is okay?
At idling, the engine should be steady and not frequently fluctuate in RPM. There should be no jerks in the acceleration. There should be no leaks, and the levels of coolant and oil should be appropriate. It should crank easily when starting. If the engine smells, smokes, or vibrates excessively, there could be a problem.
4. How to check a second-hand car engine?
Make sure to examine the engine for noise, smoke, and vibration before purchasing a used vehicle. Look for coolant and oil leaks by opening the hood. Match the engine number to the RC. Take a test drive and feel whether acceleration and gear shifting are smooth. It’s best to have a mechanic perform a compression test.
5. What’s the average cost to repair an engine?
The cost of repairs depends on the damage and engine type. Typical repairs cost between 15k to 50k rupees, while critical problems, such as head or piston damage, might cost up to 1 lakh. A trusted garage should always handle repairs.
