Compression and Block Tests

[mrnickleye]

The differences are:

A COMPRESSION TEST, as you probably know, checks the compression for a cylinder. Do them all to compare measurements.

Connect the compression gauge to the spark plug hole.

With all spark plugs removed, and the coil(s) disconnected, or ground the high tension lead(s), Test by cranking the engine over for a few revolutions.

Write down your findings.

Look at (and remember) the first jump of the needle. This jump will check the condition of the valves (good, or bad).

90 psi is great for first jump. If one or two are below 70 psi, and the rest are like 80 psi or more, I'd be concerned.
60 and below is very likely a burned valve.

Then note the final psi on the gauge. Do it again 3-4 times for an average, for each cylinder.

After doing all this, do it all over again, but (using an oil squirt can) squirt some oil (about 1 ounce) into each cyl before testing it. This seals the rings.

If the final #s come up alot, then the rings are shot.

Check the TSRM for 'normal' readings and compare yours.
http://www.cygnusx1.net/Supra/Librar...ction=A&Page=3
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A BLOCK TEST is done to check the cooling system to find out if any combustion gasses are getting into it.

A 'block test kit' is used. The coolant level is lowered in the radiator a couple of inches. A chemical (blue)is placed into the tester's glass tube, which looks like a big eye dropper.

Then, while the engine is running, the tube is placed over the radiator opening, and the rubber bulb is squeezed several times, sucking in air from the radiator. This sends bubbles thru the blue liquid, and if it turns green or yellow (doesn't stay blue) then you have combustion gasses leaking into the cooling system.

It will be the head gasket (most likely), or a cracked head.