Reasons for a Rebuild
There are two main reasons people choose to rebuild an engine: wear to engine bearings, and poorly seating piston rings. The moving parts of the engine (such and the crankshaft, rods and pistons) are mounted on bearings that allow them to move freely. These bearings are lubricated by engine oil. Bearings are built to last many thousands of miles, but they do experience wear after time. This wear is accelerated exponentially when a vehicle is poorly maintained and is run on low oil levels or the oil change schedule isn’t properly followed.
Worn bearings produce loud knocking and eventually can cause a destructive failure of the engine. Piston rings seal in the expanding gasses created by the burning of gasoline within the engine. As Piston rings wear, they no longer seal the cylinders properly, resulting in a phenomenon called “blow-by.” Blow-by occurs when crankcase oil escapes past worn rings and is burned with the fuel mixture in the cylinder. Often this is the reason that older engines have an excessive amount of smoke in the exhaust.
Is it worth it to rebuild or repair my engine?
Most of the time it comes down to a personal choice. There is no good formulaic solution to the question. There are cases where it’s an easy decision. If the car is 20 years old with 300,000 miles on it and is falling apart at the seams then it’s pretty obvious it makes no sense to fix it. If the car is 5 years old and in good shape it’s definitely worth fixing. Most of the cars that need engines fall somewhere in-between. Our best advise is to have a full vehicle inspection done before having the engine repaired, then consider the total projected cost of the engine plus any needed maintenance and repairs. Consider whether you like your car or not and the cost of buying a new or used car you would like. Keep in mind that there is some uncertainty in buying a used car even if you have it inspected. Remember to include financing costs and full coverage insurance when thinking about a new car. In some cases it is worth doing repairs to a car in excess of its bluebook value.
What’s Done during an Engine Rebuild
When an engine is rebuilt, a few basic things are done to restore it to good working condition. First, the “short block” or lower half of the engine is removed and sent to an automotive machine shop. At the shop it is disassembled and cleaned so that the condition of the block can be properly assessed. Depending on the condition of the internal parts of the engine, the piston rings, bearings and sometimes the pistons themselves are replaced. The internal surfaces of the cylinders are also reconditioned to ensure that the new piston rings can form a proper seal with the cylinder walls. Finally, the engine is reassembled and installed back in the vehicle. Often the cylinder head is also reconditioned at the same time.
Signs You May Need a Rebuild
There are some frequently seen signs that a rebuild may be necessary for your engine. The most common sign is oil consumption and excessive white smoke in the exhaust, especially when the engine is cold. This is normally a sign of worn piston rings. More extreme signs could be metal shavings in the engine oil (a common sign of dangerously worn bearings) and “knocking” or “chattering” from the engine bearings.
Remember that a rebuild can be very expensive and it might not be the right choice for all vehicles. If you think that you might be in the market for a rebuild, you might also want to consider swapping in a lower-mileage engine or an engine that is in better condition as this option could be cheaper.
So my car will be like new, right?
Nope. The car is much more than just the engine. There’s steering, suspension, transmission, brakes, tires, axles, fuel injection, smog equipment, and a lot more. A car with a rebuilt engine will still run poorly with bad ignition wire, and still fail smog with a bad O2 sensor, and still overheat with a bad radiator.
What are the different ways of repairing the engine?
The least expensive is a ring and valve job. This is done for a engine that has lost compression in one or more cylinders or is burning oil. A ring and valve job is done with the engine block in the car. It includes removing the head and rebuilding it, removing the pistons and re-ringing them, honing the cylinder walls if needed and replacing the rod bearings. The philosophy is to repair the engine as needed. Parts that are still good are not replaced. For instance, if the valve guide diameter is still within manufacturers specification, then they are not replaced. You pay for what you get, so if your engine is less damaged then it costs less. Usually you will be quoted for the basic job and after inspection of the components you will get a call back with a more accurate estimate. A ring and valve job cannot be done if the cylinder walls are worn beyond specification, the crank is worn, or the deck surface is warped or irregular. These are things that cannot be inspected until the engine is taken apart.
How do I break in the rebuilt engine?
Vary the engine speed and load. Don’t use over 75% throttle. Don’t go over 75% of the maximum RPM. Don’t use synthetic oil. Don’t let the engine idle for extended periods. Don’t cruise on the freeway at the same speed for extended periods. It should only take about 500 miles to break an engine in. After that change the oil and do what you want. Believe it or not, how you break your engine in can make a huge difference in how long your rebuilt engine lasts and how much oil it uses. You should also be aware that the rebuilt engine will burn more oil as it is breaking in, so check the oil frequently.