How to Change a Car Engine Yourself Step by Step


Dec 10th, 2018

How to Change a Car Engine Yourself Step by Step

A car is not meant to run forever without the occasional change of parts; these parts may range from glass parts, metal parts, transmissions, clutches, panels, wiper motors to the car's engine. Should the need arise for you to replace your car's engine - whether for reasons of a damaged engine or the need to upgrade to a more sophisticated engine - you can follow these steps. The following steps will guide you in this task.

Get All the Tools You Need

You need to be adequately prepared for this process. Some necessary tools and a can-do spirit is all you need. If you have a toolkit (you should), chances are you already have the tools required to replace your engine. 

Isolate the Engine

In order to remove the old engine from the car, first, you need to isolate the engine (you have to make sure that nothing is attached to it). For you to isolate the engine completely, you have to follow this sequence:

  • Remove the Hood: First, you need to detach the bonnet of the car to provide room for any activity on your car's engine. The hood or bonnet of your vehicle will most likely be held to the body of the vehicle by four pairs of screws, two on the left and two on the right. Unscrew them and disconnect the hood, then screw them back on the hood to avoid misplacing the screws.
  • Remove the Front Bumper: You need to take down the front bumper too so that you can get more elbow room. When you take down the bumper, make sure to put the screws back where they belong, so you wouldn’t lose them or mix them up with other one screws (throughout this job, you will be removing lots of bolts so any time you take one off, make sure to put it back). 
  • Remove the Air Box and Air Manifolds: Doing this will give you a better view of the wiring of the car’s engine.
  • Take Photos: Before you start disconnecting the wires, take a picture. Replacing an engine can be intimidating especially if you are doing it for the first time. The biggest fear for most people is to remember where all the wiring's go back when it's time to reconnect them. You need to take clear photos from different angles to know the position of all the wiring and hoses, so you wouldn't mix them up when it is time to reconnect.
  • Remove the Battery: To disconnect all the wiring, first, you need to remove the battery so that you wouldn't short-circuit anything. When this is done, you can now advance to the next stage of the isolation process leading to the disconnection of the wiring of the car's engine.
  • Drain the Radiator: To do this, put a drain pan under the radiator and take off the drain plug, wait until all the coolant is drained from the radiator, then you can begin work on the cooling system.
  • Detach the Cooling System: The first thing to do is to remove the coolant hoses going in and out of the engine. You need to be very careful when you are taking off the coolant hoses because rubber hoses tend to stick tight to the pipe. You wouldn't want to break anything (you can try some wiggling, some twisting or you can apply some heat to break the bonded hose). When you are done disconnecting the hoses, you can now take off the whole cooling system, including the AC compressor. You can uncouple the compressor by sliding its pulley belt and unbolting from the engine.
  • Disconnect the Exhaust: Due to extreme heat, the exhaust manifold bolts practically weld themselves and are often very difficult to detach. Spray some WD40 and leave overnight if you experience any difficulties in taking them off.
  • Disconnect the Wiring: To disconnect the wiring of the engine, start with the wires on top of the engine and work your way down to the bottom of the engine. Take off the entire fuel rail (keep in mind that the fuel in the rail is under pressure and may squirt into your eyes). You can disconnect the wiring on the starter motor and the alternator. When this is done, you can now take off all the wiring harness from the sites so that you can have a clear view of the engine.

Remove the Engine Mounts

After removing all the wiring, you will have a clear view of the engine. You will see that there are basically two mounts holding the engine to the chassis. These mounts are located at the front of the car underneath the radiator and behind the engine below the entry point of the coolant hoses respectively. The other thing holding the engine to the chassis is the bolt underneath the transmission. 

For you to get enough clearance to lift up the engine, you need to shift the engine to the side and unclamp it from the transmission. Please note that you will need to remove all the pulleys from the engine before you can get enough room to move the engine to the side.

To unmount the engine from the chassis, you need to jack up the car and put it on jack stands. This will give you enough room to unscrew the mounts and disconnect the engine from the chassis. You can now free up the drive shafts (one from the wheel and the other one at the base of the engine). Unless you like surprises, you need to drain the transmission fluid before you disconnect the base driving shaft. 

You can now unscrew the mounts of holding the engine to the chassis of the car. Once this is done, your engine will be free and ready to be taken out of the car.

Remove the Old Engine

To remove the old engine from the car, you are going to need an engine jack because engines are very heavy. You also need an engine lever that allows you to tilt the engine at different angles. 

You need to attach the engine to the crane by using two steel chains (one under the compressor bracket and another one under the alternator bracket) and one extra strap at the transmission (to balance the weight). You can then lift up the engine with the use of the crane. You also want to look around as you lift to see if there is anything attached to the engine (you don't want to damage anything that gets in the way).

You can now source for parts (compressor, alternator, starter motor, and others) from the old engine and use them for the new engine. Make sure to clean and oil the old parts before coupling them with the new engine. Once this is done, you can now install the new engine into your car.

Install the New Engine

With the aid of the crane, lower the new replacement engine into the car carefully and work your way backward through the dismantling process. Consult the pictures you took at the beginning so you won't mix things up when connecting the wiring and hoses. When you have screwed on all bolts, you need to replace all the drained fluids. Replace the hood and bumper of the car and you are done!

Start your engine and let it run for some time to see the result of your hard work. Take some selfies - you deserve it!