lock sheild valves

[timbalcombe]

If I open all the lock sheild valves will there be a detrimental effect on the heating system?
I have a vaillant combi, si I assume the system is a closed loop?

I have done this to try and erradicate some vibration from the boiler, and it seems to have worked, as the return pipe does not vibrate so much.
I also bled some air out from the upstairs radiators.
Is it more likely that that has stopped the vibrations?

Thanks
T

 

[nstreet]

if you open all of the lockshields fully, some of your rads may not get warm, water will take the route of least resistance.