Brake issue

[Tom in seattle]

I feel the brakes on my 250 SL are soft.  If I slam them hard they will not lock up the wheels at slow speed.  The nose dives but I just don’t think brake pressure is as it should be. I have bled the lines using a mighty vac and checked brake pads which have plenty of wear left.  I’m now wondering if the vacuum cylinder is helping enough.  How do I check the assist ?  I don’t know if this is related but when I push the brake in at idle and not in gear the rpms increase about 200.  Should this occur?

[WRe]

Hi,
if the idle increases when you push the brake your brake vaccum has a leakage. Check the connections, hose, check valve, booster.
...WRe

[Tom in seattle]

I thought rom increase was probably related.  I will check connections etc.  But assuming I find nothing is it correct to assume the vacuum canister has a leak?  And if so is there a repair for other than outright replacement?