Used Engine Buying Guide

Used Engine Buying Guide

The process of replacing an engine in your vehicle can be a nightmare. From deciding on if you want a refurbished or salvaged engine, to determining compatibility, the sheer amount of steps that need to be taken can be overwhelming, not to mention the potential money pit that your beloved car can become. When replacing a engine, often times it is most economical to simply buy a used engine from a similar car, drop it in, and keep on engineing. However, determining where you should buy the engine from, and what information you need to gather can be intimidating. Not to worry, we’re here to help.

Step 1: Verify which engine you need.

There are several ways to verify the exact engine you need. This is a crucial step as the same series of engine may be used in different cars, often times the engine will only fit that specific model of car, as there can be differences in manifolds, emission equipment, and mounting points. You can verify which engine you need through a number of processes.

  1. Check the engine in your vehicle for markings such as a series or part number. On many engines there is a code or part number stamped into the block, and using this number can ensure that you get a compatible engine with your vehicle.
  2. Check which engine came in your car by your VIN number. There are services on the internet that can decode your VIN and show you which engine came in your car from the factory. A dealership can also provide this service with a quick phone call.

Example of a block stamped engine code.

Block Stamp Example

Step 2: Check for the engine you need, from both local suppliers and online vendors.

  • At this point you must decide if you want to go with a rebuilt/refurbished engine, or a salvaged engine. A rebuilt engine is reassembled with new parts to make it as close to new as possible, and a salvaged engine is just one that has been pulled from a running car. A rebuilt engine is probably the better option, but is also more expensive, and it may be difficult to verify the quality of the work that was done.
  • Many people may look to their local junkyards for a replacement engine. This may not always be the best option, as many of the cars that make it to the junkyard may have ended up there due to an engine issue, and it is impossible to check if the engine is running while you are there. On top of that, you may have to pull it yourself.
  • A simple web search consisting of the phrase “your engine part number or code” followed by “for sale” should return many online vendors that carry those engines. Often times people may be hesitant to buy a engine that they cannot physically inspect, but it is important to consider that an online seller has to stand by their product, and it is a huge inconvenience to have to refund a buyer and arrange for return shipping if the engine is delivered in a defective state. Shipping costs may be an area of concern, but often times you can save money by getting it shipped directly to the shop that is performing the work, or by picking it up at a local freight center.

Step 3: Ask for information about the engine.

  • The supplier should be able to provide information about the engine including the mileage, which car it came from, the condition of the engine, and any applicable warranty.
  • If possible, ask for pictures of the engine. The pictures can tell a lot about the condition of the engine, including any physical damage or leaks.
  • If you are inspecting an engine locally or at a junkyard, there are a number of tests you can perform. These tests will already have been done by the supplier in some cases. These include:
    • Pull the oil cap and look for sludge buildup in the head.
    • Pull the spark plugs and check their condition. Poor condition plugs can indicate lack of servicing to the engine.
    • If you can, take a ratchet to the crank bolt and see if you can turn it by hand. This will ensure the engine is not seized and can turn freely.
    • If possible, pull the oil pan and check for any metal, as well as the condition of the oil. Clean oil and no metal shavings are a good sign.
    • Visually inspect the engine bay for signs of leaks and damage.

Example of damage to engine bay, in this case the vehicle was the victim of an engine fire.

Example of damage in engine bay.


Step 4: Leak down and compression testing

These two tests return arguably the most important pieces of information about the health of an engine. A compression test ensures that the engine can build enough compression in the cylinders and that it is not escaping. This test, if done cold, can be slightly misleading. A warm engine causes components to expand, thus making tighter seals around problem areas. It is for this reason that a leak down test can be more valuable. A leak down test identifies how much air is escaping from the engine, and also helps to pinpoint the exact areas that are causing the leak. If possible, the results from these tests should be sought after and weighted heavily when purchasing a used engine.


Leak down test being performed.

Step 5: See if any additional work has been done to the engine.

A supplier may have performed additional services to the engine to eliminate possible problem areas for the purchaser, such as installing a refurbished cylinder head, or replacing the timing belt as well as other gaskets that may have been leaking or are recommended to be replaced based on mileage or age of the engine. A service that is greatly valued on direct injection engines is a walnut blasting of the intake valves, since this is a known issue on these types of engines due to the lack of fuel washing of the intake valves. If these services have been performed, that engine is most likely a better choice as it has been inspected and serviced, as compared to one that is simply pulled from one car and installed into another.


Example of an engine with a refurbished cylinder head.


We hope you found this guide to be interesting and informative. If the steps are followed in this guide, the engine buying process can be transformed from a huge headache to a light breeze of a project.

At ALLMAG Auto Parts, we pride ourselves on selling quality used engines that will provide years of service for the purchaser. We inspect every engine that comes into stock, and attend to any problem areas. A leak down test is performed on every engine, and the results are recorded and published in the listing. We also take pictures of various angles of the engine, so you can see the exact engine you are purchasing. If the engine is direct injected, we also provide walnut blasting services when the engine is removed from the car. The mileage and VIN numbers are also recorded and available for the purchaser. We take the extra steps to do these services because as enthusiasts, we feel that they are of great value when purchasing a used engine. We think like enthusiasts, because we are! We want to provide the easiest process possible when purchasing a engine and we strive to improve on that process as best we can.

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