I rented the kit and filled the block with coolant. Aired it up to 40 psi like the directions direct. I can't find any leaks. I have put soapy water around the cylinders and haven't seen any bubbles. I left a halogen lamp on the valley over night to heat it up like they suggest then pressurized it. Still doen't see/hear any leaks out of the cylinders.

The thing is if I come back an hour later and press the shrader valve no air comes out. Where could the pressure be going? Any ideas?