1973 Mach1 Block Check Combustion Gas Test For Cooling Systems

In this video I show how a "Block Check" is performed, using a 1973 Mach 1 Mustang that is NOT overheating. This video is meant to show how to use the Block Check test unit, not to actually diagnose a vehicle with a live overheating issue. The test process is the same, or at worst similar, for pretty much any automotive or truck internal combustion, water cooled engine. The idea is to put a test solution that is reactive to Carbon Monoxide (CO), a byproduct gas of combustion, into test cylinder, then dray air from inside a cooling system through the test solution. These Block Check test kits are usually available at many auto parts store for loan, to rent, and/or for purchase.
Side note, to clarify that is going on in this video, I only performed the Block Check on this 73 Mach 1 to how it is done, not to diagnose an overheating issue with this particular vehicle. In fact, the 3 row aluminum radiator, dual electric fans, and variable thermal switch using a thermocouple inserted in the upper radiator hose have performed wonderfully even on hot days when the air conditioner is running, and I am driving at slow speeds or during prolonged periods of idling.
If the color of the test solutions remains its original blue color, no combustion gas is present in the cooling system. If, however, the test solutions turns to a green or yellow color that shows CO is present, which indicates a failed/blown head gasket, a cracked head, and/or a cracked engine block that is allowing combustion gas to leak into the cooling system.
Because this is performed on a running engine "at temperature," and moreover because being tested is an indication there is an overheating issue already, care must be taken to prevent personal injury due to accidental burning, and to monitor the engine temperature to prevent damage to the cooling system or engine in general. Leave the engine running "at temperature" no longer than absolutely necessary to perform the test to help avoid overheating, especially in case there is a combustion gas leak into the cooling system as that will allow the coolant temperature to spike quickly.
In this video, after testing the cooling system, which shows no CO is present, I place the tester at the end of the exhaust pipe of a running engine to demonstrate the color change in the test solutions in when CO is present.

[@blue73mustang]

Great video and as always good information . I hear the electric fans coming on . The car sounds great 👍🏻

[@gilberthale7777]

Yes, that is our dual electric fan array turning off and on as the coolant temp thermostat causes the fan relay to turn on and off. I have two other videos that may interest you. One shows us installing our dual electric fans, 3 row aluminum radiator, and how we wired the fan relay. The other shows how to wire in an LED light to show when the electric fans have been turned on.
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