3 Cylinder Tests
Compression test:For testing rings and valves. It is done dry,and then wet with regular engine oil added in equal drops per cylinder. This test does not do well to test for coolant leaks.
Leak-down test: which pinpoints leaks and loss at the valves, rings and can test the head gasket/porous heads and the like...
A tool that is run off an air compressor is installed to a plug hole with that clyinder on TDC. The tool has a gauge and a regulator so full psi does not enter the engine. You would listen to the carbs/intake port for injection, the exhaust, the oil cap, and in this case the radiator cap would also be off and hissing/bubbling no doubt. (If the engine has a porous head, crack in the cylinder, or a blown head gasket, there is no way to confirm which is which with this tool, but head gaskets commonly go. There is the chance the head gasket is OK and the problem is either the crack, or the pours idea.)
Pressure test to the cooling system: A pump type adapter is installed on the radiator filler and sealed tightly. This tool also has a gauge, and is pumped upto coolant max pressure, and allowed to sit and leak down for a time. With the plugs out, you can hear a hiss, and sometimes see coolant appear in the cylinder that is affected. A leak-down can pin point the source of the leak.
Once it is determined there is such a leak, the head must be removed with care to not harm the head gasket. Once the gasket is off, itwould be inspected closely looking for defects. Examine both sides for traces of coolant, which indicate where a defect may be.
You will notice coolant made a marking on the gasket sides (upper/lower). Thoroughly clean this area before a new gasket is installed.
The head should be checked for warping and decarbonized.
Coolant and oil do not mix well. Pistons and bores should be cleaned of coolant or hot spots form as oil is pushed from these surfaces where coolant was in contact.
Coolant to a engine is much like oil on a cement driveway. When it rains, you can see the water run from the oil spot.The same occurs when coolant adheres to metal cylinder. Oil no longer will lube that area. It must be cleaned.
Another test is a chemical test where a tool is installed on the radiator filler and contains a liquid that changes color in the presence of exhaust in the coolant.