i'm in the process of working on my 93 fd. trying to get the engine bay nice and clean and looking great while the engine is out. for awhile i've noticed a rusty spot on my brake booster and the other nite while working on the car i removed the brake booster and noticed more rust toward the bottom of the unit. i bought the car as a project and have never been able to test the brakes so i'm not sure if they work fine or not. i know the brake fluid reservoir was very low on fluid. i'm wondering if there's a way to test the brake booster before i begin reassembling it.
yesterday i took off the reservoir, mc, and associated brackets and sandblasted everything so i can repaint them. i've started painting the parts but, now i'm wondering if maybe the brake booster if failing or bad. i'm just wondering if i can test the brake booster some how before i finish painting and reassembling everything.
anyone have any ideas? when i took off the brake booster i pulled the master cylinder and noticed the O ring on the end of it. should that be replaced when reassembling?

 

Generally speaking...you'll want to put a vacuum source on to it to make sure it doesn't leak.

 

its pretty simple, put a vacuum on it, and it should hold it.

 

so do i need to reassemble everything and put some fluid in the res then do this?

 

nope....not if all you are testing is the booster mechanism.

The booster is a completely separate mechanism from the brake master cylinder, of course. The master cylinder is a whole 'nother animal, and much more complex. And yes, it is a good idea to replace ANY 'O' ring/seal when