When should a car engine be replaced?

This blog will answer the question “when should a car engine be replaced” and provide the issues and scenarios for identifying a failed engine for replacement and specify the benefits of opting to replace your engine instead of purchasing a new car.

When should a car engine be replaced?

A car engine should be replaced

 if the existing engine seizes or fails to propel forward. These problems might be due to the engine’s age or might be noticeable through high pitched noises and vibrations, leakages, engine stalling, etc. Engines are mostly driven upto 150000 miles before the engines’ systems and parts begin to malfunction completely.

Symptoms of Engine Failure     

Abnormal Noises

If any excessive vibration or common misfiring occurs even after replacing the necessary spare parts initiated the problems. Commonly. The parts associated with the above two mentioned problems are:

  • Spark plugs
  • Fuel injectors
  • Cylinder Block/Head and its related parts 
  • Air filters
  • Oxygen, throttle body, and MAF sensor, etc.

Cylinder block and its associated parts, such as the combustion chamber, piston, crankshaft, timing belt and gears, etc., are critical to the engine’s operation.

Any severe damage to these parts or their operation can switch on the check engine light and cause the engine to produce abnormal noises and vibrations like loud knocking sounds. 

They are caused by unburnt air-fuel mixture that combust after the combustion stroke gets completed, this action causes the engine to produce extremely loud knocking sounds.

The recurring issue with failing engines are broken or damaged engine bearings. Since, failed engine bearings can cause all engine parts to get succeptible to damage and create failure in operation. 

It is important to note that replacing these parts is not a viable option due to the high cost of parts and repair associated with these problems. Hence, it is best to consider replacing the engine itself. 

Deteriorating Fuel Efficiency

Fuel Efficiency reduces when the engine ages and the vehicle starts to lose its mileage, i.e. car consumes more fuel than it ideally does. This reduction of fuel efficiency occurs due to problems faced by the integral parts of the engine related to calculating, measuring fuel dispersion and flow rate and storing fuel. If the problem persists for an extended period, replacing the machine will be the most suited option.


Engine Stalling and Stuttering

An engine requires help if it stalls or stutters. This occurrence corresponds to the integral parts of the engine not operating efficiently to ensure the vehicle attains power and propels without any abnormal disturbance. 

You can opt to replace the entire engine before these types of issues occur since engines can stall even in the middle of their commute through a congested highway with vehicles. This event can cause catastrophic problems for the passenger vehicles and your personal vehicle itself. (Arora 2020)

Fluid leaks 

Fluid gets depleted when the hoses, joints, and fittings face excessive wear and tear. Clouds of black smoke emitted from the tailpipe correspond to leakages and incomplete combustion occurring in the engine bay. 

Other common leaks are head gasket leaks and engine oil leaks. It is worth observing the colours of smoke from the exhaust tail pipe, you must note that if various colours of smoke are found regularly, this corresponds to multiple leakages present in your engine. 

This issue can either be addressed by conducting a complete rehaul of the related parts or replacing the engine. Rehauling all internal factors related to fluid leaks can become a highly complex task. So, replacing the engine is a viable option to solve this problem.

Pulley Bearing and Belt Failure

Several mechanical operations occur in the engine bay using the pulley system to transmit motion from the crank pulley to the other pulleys, such as the Alternator pulley, Air conditioning pump pulley, Power Steering, and Idler pulley. 

These pulleys also accommodate bearings to aid the serpentine belts to move smoothly and seamlessly around the pulley. But once the vehicle runs more than 50000 miles, bearings and belts get worn out, or the tension of belts reduces, causing the engine to produce a high-frequency noise from the Serpentine Belt.

Benefits of Replacing An Engine

When you choose to replace our engine instead of purchasing a new vehicle, you obtain numerous benefits specifically in terms of expenses; the total costs incurred acquiring a replacement engine are significantly lower than buying a new car.

The replacement engine must have enough capacity to run as much as the original engine, ensuring all systems are in top-notch mechanical condition. It should run the same amount of kilometres as the initial engine. 

With the current market, you can easily find an engine with similar mileage to swap it with the existing engine on your vehicle. If only the engine is replaced instead of the vehicle. You reduce a considerable amount of costs from your overall expenditure. 

The benefits of swapping engines are listed below:

  • Total incurred costs due to taxes, insurances and other charges are all neglected when replacing the engine instead of the car. 
  • You can swap your vehicle’s engine if its other parts are in optimal working condition and if the car might be in service for an extended period. 
  • Engines can either be replaced after reaching a fixed mileage or after the engine fails. 
  • The remanufactured engines are an excellent option to swap your existing old machine that is on the verge of failure. Since it runs as much as the current engine, it doubles the vehicle’s service life.


In this blog, we have addressed the question “when should we replace an engine” and provided a brief description of the issues that can cause an engine to fail and when you must replace your engine. Adding to that, we determined that most topics leading to engine failure are related to incomplete combustion or disruption during one of the strokes. Finally, we discussed the significant benefits of swapping your vehicle’s engine instead of purchasing a new car.


  1. Arora, Vaibhav. 2020. “When is the Right Time to Replace your Old Car? Telltale Signs.” GoMechanic. https://gomechanic.in/blog/when-to-replace-your-old-car/.
  2. “Engine Replacement or Car Replacement?” 2013. Central Avenue Automotive. https://www.centralaveauto.com/engine-replacement-or-car-replacement/.
  3. “Replacing Engines Instead of Buying New Vehicles – Maintenance.” 1999. Automotive Fleet. https://www.automotive-fleet.com/147285/replacing-engines-instead-of-buying-new-vehicles.
  4. “SERVICE & PARTS GUIDE.” n.d. Mitsubishi Motors. Accessed December 28, 2021. https://www.mitsubishi-motors.com/en/maintenance/pdf/Mitsubishi_PARTSandGUIDE.pdf.