No pressure after opening coolant cap

check for leaks. check at the water pump, at the "weep hole"

you can pressure sheck the system as well, that'll force out any coolant from a leak.

make sure too, the system is topped off first

 

Engine Fan On?

 

If the temp is below 170. You probably won't have gas to release.

Not that there's any gas to release.

I always kick the fan on if I need to pop the cap for whatever reason. 170 or lower before I take it off.

 

Cap may not be holding, most are made with a prv set to pressure of x amount of relief 8,10,13 psi , should the relief spring break then the psi will be lower or none at all.

 

Why are you opening it?

 

Supposedly there's only one cap these days and it's rated for 15.

Reservoir cap.

Unless it's an actual radiator fill with a cap.

 

You're constantly removing the cap. Why are you constantly removing the cap?

 

Are you undoing the Radiator cap? Or the expansion tank Cap..??

 

Replace the cap, it is not working.