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A vacuum gauge is a useful auto accessory that helps to diagnose the state of an engine’s running parameters. When the vacuum gauge is connected to the engine it must be via a constant vacuum source. Certain engine manifolds have a removable plug that can be employed with the vacuum gauge. Alternatively, the vacuum gauge can be connected to the engine via the positive crankcase ventilation, or PCV, hose. The engine should be allowed to reach full operating temperature before any measurements are taken.
In general terms, a high, steady vacuum reading is indicative of a healthy engine, whilst a low vacuum reading is likely to mean that the engine’s piston rings or oil rings are worn.
Specific engine conditions that may be revealed through the results of a vacuum gauge test are sticking valves, burnt valves, worn valve guides, weak valve springs, vacuum leaks and problems with the engine’s cylinder head gasket.
Whilst there are more sophisticated, in-garage methods of testing the state of a motor vehicle’s engine, the vacuum gauge is a cheap and relatively straightforward way for an owner to keep a regular check on the engine. Employing a vacuum gauge can help to identify engine problems early and avoid expensive repairs or even engine replacement in the future.