Testing Used Engines
The question asked most often by people searching for a used Japanese engine is “how many miles on the engine?” This is a legitimate question, but really not the most important one.
Far more important is the quality assurance measures a company takes before selling you an engine. What kind of inspection does the company perform? And most important—“How does the company test the engine?”
For a quick analysis of a used engines state and quality you can measure cylinder and oil pressure.
Cylinder Pressure—a pressure gauge is connected to the engine cylinder at the spark plug opening. Pressure is measured at each cylinder in terms of pounds per square inch (e.g. 180 psi). The variance between cylinder readings should not be greater than 10%. If it is, a leak-down test would be performed to locate a potential pressure leak in the rings, valves, block or head gasket. Both of these tests are done when the engine is not running.
Oil Pressure—proper oil pressure in a used engine is a great indicator that the internal components are in good shape. Certainly an engine cannot ship with poor oil pressure and in fact much more detailed inspection would be required if low pressure was detected in a used engine.
The best test that a supplier can perform is a hot-run test
. This is a live test where the engine is bench mounted and started up
. This requires custom equipment and skilled automotive technicians to perform it properly. That is why very few companies can provide this level of quality assurance.
The quality control program employed by Rising Sun Engines, Inc. includes the following tasks:
1. External components are carefully removed from the engine long block. These components cannot be used in the USA. The vehicle owner will swap over their external components to the used engine supplied to them.
2. All external openings are plugged. The entire engine is loaded into a jet-wash machine (basically a big dishwasher) and the outside of the engine is thoroughly cleaned.
3. The cleaned engine is mounted to the company’s exclusive hot-run test bench. It is first run without the exhaust manifolds so the technician can check for smoke from the engine. Once the exhaust system is installed the engine is run again and oil pressure is measured while the engine is running. With the exhaust system in place the technician can listen for abnormal noises from the engine.
4. While the engine cools the technician inspects the engine for obvious leaks, broken parts and checks the valve guides after the manifolds have been removed to make sure no oil is passing. Compression is measured and recorded.
5. A final inspection is preformed prior to shipment to ensure that it is clean, all items are included and all the paperwork (including customer provided test results) is attached.
A great deal of time and effort should be invested in each used engine being shipped. Assuring the quality and condition of the engine is the best way to answer the question about mileage.