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How to Perform a Compression Test on the Engine in a Chevy Silverado

by Contributor

The Chevy Silverado comes with either a V6 or V8 engine, and it is important to keep the vehicle running properly to get the most out of these powerful engines. A compression test is an easy way to find out what is wrong inside of the engine without tearing it apart. Worn piston rings, cylinder walls and valves are common problems diagnosed by performing a compression test.

Turn on the engine in the Chevy Silverado to warm it up, since a compression test performed on a cold engine will be inaccurate. The battery should be in good condition so you can spin the engine several times.

Remove all eight spark plugs from the V8 engine after it is warm and turned off. Models containing a V6 engine have only six spark plugs. Disable the ignition system to eliminate the possibility of electrical shock while performing the compression test.

Insert the compression tester into one of the spark plug holes and crank the starter so that compression builds in that cylinder. Write down the compression number for comparison later and continue to the next spark plug hole. Repeat the procedure for each of the six or eight cylinders, recording each number.

Compare the compression numbers to manufacturer specifications. If the Chevy Silverado contains a 4.3 L V6 engine, the ideal compression ratio is 9.2:1. If it contains a V8 engine, the ratio varies by engine size. A 4.8 L engine is 9.5:1, a 5.3 L engine is 9.5:1 and a 6.0 L engine is 9.4:1.

Evaluate the difference between the recommended compression ratio and the test results. An ideal reading falls within 15 psi. Compare the numbers with each other as well. They should be within 10 psi of each other.

Retest any cylinders that show a low reading by adding a tiny amount of motor oil to the cylinder, then running the compression test again. If the resulting number is higher than the first, then the engine has worn cylinder walls or piston rings in that cylinder. If the number remains the same, then the engine has worn valves or valve seats.

Tip

  • The compression ratios listed above refer to model years between 1999 and 2006. When performing a compression test on a newer model, the recommended numbers change for all engines except the 4.3 L V6 engine.

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