Compression and Leak Down Test - Schrader valve

[YoshiMoshi3]

When doing a compression and leak down test, what tool requires a Schrader valve? Isn't the Schrader valve requried to release pressure prior to removal of the air hose attachment adapter for the spark plug hole? Otherwise without releasing the pressure first, it could go flying and result in injury?

Is this correct?

 

[dmaxfireman]

A compression test requires a schrader valve. A leak down test requires there not be a schrader valve. There is a release valve on a compression tester to release the contained pressure. On a leak down tester the regulator bleeds off the pressure when you dial it back down.

 

[cgrutt]

I'm not a pro and would have to look to confirm but believe the hose on compression tester has a valve (not an external Schrader but internal) so the gauge holds reading. Leakdown is controlled by manifold and does not have valve.

@dmaxfireman beat me to it.

 

[YoshiMoshi3]

Thank you!