Does a block test and a compression test detect the same thing?

Question

There is the "block test" which uses a colored liquid to test for combustion gas in the cooling system, which in turn tells you whether you have a head gasket that is blown...and then....there is the engine cylinder compression test which measures the engine pressure or the pressure the cylinders are generation...this also, among other things, tell you weather you have a faulty head gasket or cylinder head.
Correct me I'm wrong but I'm thinking these two tests, well...test for the same thing....right?
Reason i ask is cz im trying to find out if i have a faulty head gasket/or heads and i only have the "compression tester"....i cant find the "block test" where i am here.

So are they the same?

Answer 1

No. Block Zyglow test detects cracks in the cylinder block. A dry compression test detects worn cylinders and piston rings. A wet compression test will tell if the valves or valve seats are leaking.

Answer 2

The block test is specific for leaks from the combustion chambers to the cooling system, while the compression test checks for all compression faults including bad rings, burned valves, bent connecting rod.... A bad head gasket may not show up on a "crank and measure" compression test but will usually show up on a leak-down test. Small breaches in the head gasket will not be detectable on a leak-down test though. The block test is definitive: if the block test says there are hydrocarbons in the coolant the head(s) have to come off.



I have had 100% success with a much simpler screening test. Remove the pressure cap when the engine is cold and, if the vehicle does not have a surge tank, clamp closed the hose to the reservoir. Start the engine and place the palm of your hand where the pressure cap was. If you feel steadily rising pressure within five seconds there is a head or head gasket problem. If not, all is well.

Answer 3

a Leak Down test will accurately test for head gasket or warped head.



Your problem is primarily caused by lack of cooling system maintenance.

Answer 4

not really as the compression test is more for testing ring condition and valve sealing. You should see leaking head gasket as white smoke from the exhaust or milky oil, also if you let it idle for 30min it should overheat.(obviously watch the gauge and don't let it get too hot.)

Answer 5

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Answer 6

a compression test determines if the rings and valves are good and the block test determines if you have any antifreeze leaks !