hi got a couple of quick questions on my power brake booster unit........Seems i have pleaty of vac coming from the intake but the brake booster unit is not keeping any vac after the motor is shut off............Also never have had very good power brakes and a buddy accross street just pulled the fitting off the booster and told me about it not keeping the vac and that it should,,,,,,, we went over to his chevy truck and he showed me that he had a bunch of vac on his..........so do i have a bad diaframe inside of the booster or something else...............The rubber seal does have cracks in it around the elbo fitting but i dont hear any vac leaks when the motor is running...............One more thing, on old 4 cyl motor that was in the scrambler before i swapped in the sb chevy the hose from the intake had about half way to the brake booster unit a small round canister that looks like a little barrel and i just left it............my buddys truck just had the hose running all the way from the intake to the brake booster............. What is this thing and do it need it or could this be causing the problem...............I am planning on taking it out to see if that helps.......... I will get some photos on this what do you think..............should i be looking for a new brake booster unit thanks

hi here are some photos of my unit on the cj and a couple of pic of some units i have found on ebay , the one of the vac booster only is a new jeep for a cj and the other is the kind of units i am finding sold as a complete unit..........i am thinking the new one should fit as a replacement for my unit as my master cyl is working ok.......

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If you have good boost on the brakes with the engine running, you may just need the little valve that is on the booster that the hose attaches to. No need to pull the booster to get to that. That valve is a one way valve that is supposed to retain the vacuum in the booster when the vacuum supply quits. If you hear a hissing sound from the inside of the jeep at the firewall then the booster is leaking. Those are the two most common ways it fails. Start with the valve though.