When to replace a car engine?

This blog will answer the question, ‘When to replace a car engine?’, and cover topics like standard operating procedure for replacing a car engine, and cost of replacing a car engine.

When to replace a car engine?

These are the following scenarios when the replacement of an engine should be considered:

  • In case of thick and dark smoke comes out from either the engine or the hood, it is a telltale sign that the engine needs an immediate replacement and you should visit a professional mechanic.
  • Another case of immediate engine replacement is when a repeated and distinct knocking sound is heard from the engine. This sound is indicative of the engine bearings failing and that the engine is in dire need of a replacement.
  • Often it has been noticed that the engine suffers from sudden fuel consumption and low mileage. This is indicative of an engine fault that is causing all the liquids inside to mix with the gas.
  • If an engine causes a stuttering sound, it needs replacement with immediate effect as this means that the internal components of the engine that support it are aging and won’t be able to go on for long.

Standard operating procedure for replacing a car engine 

An engine replacement is divided into three parts. They are as follows:

  • Removal of the old engine
  • Installation of the new engine
  • Connections of the new engine

Removal of the old engine

The removal of the old engine involves the following steps.

Taking out the hood

Before starting any kind of replacement work, it is necessary to first remove the engine hood as doing so creates more work space and makes lifting the engine easier. The hood can be removed easily by unhinging it from the sides indicated by about three such bolts.

Draining all the fluids

The next important step is to be able to drain all kinds of fluid from within the engine. This should be initiated by draining out the engine oil by collecting it in the oil pan by means of the oil drain.

The coolant can be collected from the radiator while the washer fluids can be left as it is .

Disconnect all the inlet, outlet, and coolant connections

It is important to open or disconnect all connections to the old engine. Disconnect the inlet pipe from the throttle and the outlet pipe from the exhaust manifold. Also, make sure to disconnect the coolant supply coming from the radiator.

Remove the battery

The car battery needs to be removed to facilitate disconnecting all the wiring to avoid causing a short circuit.

Remove the engine mounting bolts

Next, we must remove the engine mounting bolts, which are a pair or three such bolts holding the engine to the transmission line and chassis.

Remove the old engine

The old engine now devoid of any connections or wiring can be lifted either by an engine jack or an engine hoist.

To perform the removal of the old engine from the car, an engine jack needs to be used due to the sheer weight of the engine. We will be needing an engine lever that enables tilting the engine at angles according to our requirements.

The engine needs to be attached to either a crane or the hook of the hoisting machine, attaching it under the compressor bracket and under the alternator. One surplus hooking needs to be done for the transmission.

Installation of the new engine

The following steps need to be followed to perform the installation of the new engine.

Compare the two engines

It is important to compare the new engine with the old one to check for the same size, connections, and wiring. Check if all the components like the transmission, alternator, and the location of all the valves are similar to the old one.


Firstly, it is important to reconnect and rejoin the motor bolts along with linking the engine to the transmission and chassis. Perform everything similar to the dismantling process but in a similar manner

Establish all the connections back to the new engine

It is important for the engine to now get connected to installing the intake and exhaust valves and also the radiator and coolant.

Next, the coolant supply line to the engine should be connected and engine oil and coolant should be added according to the user manual.

Cost of replacing a car engine

An estimated cost of replacement for a car engine can range anywhere between 3200$-5500$.

Cars with a complex engine setup can suffer a cost of up to 6000$ for an engine replacement, while cheaper and compact cars like the four-cylinder ones take only up to 4000$ to perform a replacement on.

Research has shown why an engine replacement is an expensive process and is a potentially big investment. This is why the symptoms of an engine replacement should be identified earlier and dealt with.


We came to understand the exact signs to identify the need for an engine replacement and also came across the standard operating procedure for performing an engine replacement. Furthermore, the costs of conducting an engine replacement have also been provided. Please feel free to comment on the content or ask any questions in the comments section below.

Frequently Asked Questions (FAQs): When to replace a car engine?

Is it worth it to change car engine?

Yes, this is because changing or replacing a car engine presents a more long-term approach and is also a reliable solution. Although an engine should be repaired or serviced at the first sign of problems as it can be an expensive set of repairs if ignored for long.

Does replacing engine reset mileage?

No, replacing the engine does not reset the mileage as the odometer measures the aging of all components of a car rather than confining the measurement to the engine only.

How long does it take to replace a car engine?

It takes roughly about 10-15 hours to completely replace a car engine, although that is entirely dependent on the brand of the car used and in what condition it is being replaced.



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