Weak brake pressure (whats up with the vac pump on the side of the block?)

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Old Aug 14, 2008 | 05:57 AM
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Default Weak brake pressure (whats up with the vac pump on the side of the block?)

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
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Old Aug 14, 2008 | 06:13 AM
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Default Check for leaks...

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.
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Old Aug 14, 2008 | 06:16 AM
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Pull the vac pump and replace the o-ring. It's probably hard after 20+ years. Clean the spring too.
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Old Aug 14, 2008 | 06:25 AM
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Default I noticed a bit of oil leakage where the vac pump mounts to the block, would this indicate

a vac leak there? I wasnt sure if the pump is sealed within itself or not...
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Old Aug 14, 2008 | 02:17 PM
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Yes sir.
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