There are many times throughout the world today that people are told they should replace their engine. There are many reasons this is recommended to vehicle owners rather than simply repairing the engine that is originally in the vehicle.
Common reasons for recommending replacement vary from mechanic to mechanic but at the heart of the matter it normally boils down to two factors, the cost of repairing the old engine and the time involved in repairing the old engine. If the original engine has failed because of internal problems, such as the oiling system failing because of lack of service or the cooling system failing allowing the engine to overheat, the repair of the original engine might exceed the amount of money the owner has available to correct the problem.
One instance where replacement of an engine might be recommended is in the case of a common head gasket failure. When broken down into individual costs: removal of the cylinder head, sending the head to a machine shop to have it magna-fluxed to check for cracks, pressure tested to check for leaks, having the head skimmed to ensure the mating surface is flat, cost of the head gasket itself including other gaskets needed to complete the repair, and all labour involved for time spend to complete the repair. Adding all of those items up it may be more beneficial to find and purchase another engine (either reconditioned or second hand) remove the old one and install the new one. Labour times may be found to be less to replace an entire engine than it is to replace a head gasket, the cost of all the bits and machine work might be found to exceed the cost of a replacement engine. In this case it would be more beneficial to not only the vehicle owner but to the garage itself to remove the old engine and install a replacement engine in its place.
At the end of the day, through a garages point of view, ramp time equals money. The time it takes to remove and send the cylinder head away to have the necessary machine work done equates into a loss of income for their business. So if they can locate and install a replacement engine in less time, the garage will normally lean towards that avenue as it is the quicker more convenient option for both the vehicle owner and themselves. They can complete the exchange and then be able to move on to the next customer to keep their garage going.
What many vehicle owners do not understand is that the costs of such jobs as a cylinder head gasket is not just a matter of taking the head off, throwing a new gasket in it and then driving down the road. A hack repair like that will have you back at the garage in very short time having the same work done all over again because the machine work had not been done.
