You will need to replace your car engine when: it has over 150,000 miles on it and is slowing down, it stops working or if it starts smoking excessively. Replacing a car engine is a complex procedure. It will require extensive knowledge of the car and its mechanical components, as well as the proper equipment and tools.
Find out the exact problem in the engine and see if the starter, transmission or other parts need replacement. If the problem is not caused by a non-engine mechanical problem, then you will need to replace the engine.
Buy or rent the right tools and equipment for the job. You will first need to buy a factory made engine, or a remanufactured engine, that is appropriate for your car to replace the one that no longer works. If you don't have all of the tools that you need, then you can either buy them or rent them from a local car center. One of the pieces of equipment that you will probably want to rent is an engine hoist and stand.
Start by disconnecting the negative battery cable in the car. Proceed with removing the top most accessible parts around the engine. Detach the distributor cover, cap, the cooling fan and the electrical harness. Unplug the fuel lines and store any excess fuel in an airtight jar. Disengage the throttle links. Give each removed part a proper code and write down their exact placement on a piece of paper.
Remove the coolant and heater hoses from the radiator respectively. Take out the AC compressor and its assembly and store it at an appropriate location. Pull out the alternator bolts and belts and disconnect the battery that is connected to it. Unbolt and remove the power steering pump.
Remove the car tires while using the jack stands for support. Put away the water pump and its pulley. Disconnect the lower radiator, power steering bracket, pump, exhaust shield and pipe.
Remove the motor mount and, once the engine is visible, drain any excessive liquid that may come out. Take out attached bolts and starter. Use a hoist to remove the engine. Place it somewhere safe. Hoist the new engine and carefully place it back in the engine compartment. Jack up the car and start installing the mechanical components that you removed in the reverse order that they were taken out. Connect the engine to the transmission. Put in the fan and the pulley. Reattach the fuel lines, hoses, alternators and the bolts. Install the AC compressor and the upper radiator hose.
Add oil to the engine before starting it up as a dry new engine can damage the surrounding parts. Let it warm up. Check for any leakage and then take the car for a test drive.
