- Joined
- May 6, 2014
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- Location
- Amoungst the Twisty Roads
When you hold the piston at TDC and add a constant flow of compressed air (100psi), that air will look for a place to escape. If something in the combustion chamber has failed, air will flow from the site of the failure;
If there is air flow from the throttle body, an intake valve or seat has failed.
If there is air flow from the exhaust, an exhaust valve or seat has failed.
If there is air flow from the engine breather, a ring has failed.
If there are bubbles in the coolant, the head gasket has failed. If it’s real bad, you can spray the head with soapy water and see movement externally. But that type of problem is usually in a non-running engine.
Some air escape is natural, that’s why if the cylinder can hold 80% or more you don’t go looking for a problem. It’s when it’s below 80% there is an unexpected amount of loss.
In order to run the rest you will need a leak down tester (Harbor Freight) and an air compressor…and a friend to hold the wrench that holds the cylinder at TDC.
If there is air flow from the throttle body, an intake valve or seat has failed.
If there is air flow from the exhaust, an exhaust valve or seat has failed.
If there is air flow from the engine breather, a ring has failed.
If there are bubbles in the coolant, the head gasket has failed. If it’s real bad, you can spray the head with soapy water and see movement externally. But that type of problem is usually in a non-running engine.
Some air escape is natural, that’s why if the cylinder can hold 80% or more you don’t go looking for a problem. It’s when it’s below 80% there is an unexpected amount of loss.
In order to run the rest you will need a leak down tester (Harbor Freight) and an air compressor…and a friend to hold the wrench that holds the cylinder at TDC.