Pre95

Ok so on the 84 4kQ the brake pressure is super weak. COming to a full stop means putting th ebrake to the floor.. almost. If you pump em a few times itll brake a bit sooner. Anyways I am wondering if the brake booster is getting any vacuum, and while I havent sprayed chem tool all over everything yet I do know all the vac system components and lines are intact. Which leaves one thing in between the booster and the intake manifold, a T junction connected to the dreaded ticking vacuum pump (this one actually doesnt tick, and considering it sat for three years I am figuring it isnt working...)

Any harm in bypassing the vac pump and running the vac for the booster directly off the manifold? Again i havent taken anything apart yet but would like to arm myself with knowledge before attacking. Any insight greatly appreciated.

I do understand that it could also be a hydraulic air bubble of some sort but figured I'd start at the easy stuff to reach to

NJRoadFan

The brake proportioning valve mounted under the master cylinder likes to spring a leak after a few years. Also the master cylinder might be leaking internally (fluid seeping around the seals inside). It could simply be air in the lines too.

PartyBoyRacing

Pull the vac pump and replace the o-ring. It's probably hard after 20+ years. Clean the spring too.

Pre95

a vac leak there? I wasnt sure if the pump is sealed within itself or not...

PartyBoyRacing

Yes sir.