Hey everyone. I just bought a 1981 280zx non-turbo 2+2.

It's eventually going to be my daily driver, and right now I'm working out these brakes. the pedal is really stiff, but that's it, they're good brakes, and can still stop the car, but I've gotta press that brake HARD.

I've got great engine vacuum. tested that yesterday. I think my master-vac brake booster is bad - i took it out and depressed the rod just like if I were pressing the pedal, and plugged the hole where the hose to the manifold goes with my thumb. if it was supposed to hold the vacuum, it totally failed. have any of y'all replaced the brake booster? do i have to use a rebuilt master-vac?

just getting into this mechanickin'. forgive my ignorance. i'm a college kid who doesn't make much money, so I'd appreciate any ideas.

 

Get one off a wreaker....

 

I replaced it with a remanufactured one and I'm happy with the results.

When I took out my broken master-vac, a ton of black oil poured out of it.

Do I need to put any oil or brake fluid in my new brake booster, or was the presence of oil there an indication of some other issue I need to fix?

 

Fluid in the booster means your master is leaking.

 

shoot.

master cylinder, really? if it were leaking, wouldn't my brake fluid be fluctuating? it's full...

 

Let me know when you come up with a better explanation.

 

well the only things connected to the master-vac booster are that center rod thing that pushes into the master cylinder and of course, the vacuum hose from the intake manifold.

is there any way BLACK oil could have gotten in there from the vacuum hose?

(i'm clarifying because brake fluid isn't black...)

 

Sure, if your oil is black, and puking out the intake or PCV valve... but if that is happening, you've got much worse problems.

Really? Brake fluid has a relatively short life, and super-short when exposed to air (like in a booster):

What Does 7 Year Old Brake Fluid Look Like? - iRV2 Forums

 

so should I just keep an eye on the Master cyl or replace it no questions asked?

yes I know it's a safety issue.

 

It sounds like you've already put it all back together... so just watch the fluid level.

Did you by chance inspect the master cylinder before reinstalling?

 

yeah, I felt around in there and it was pretty dry. but a crap ton of black stuff came out of that busted booster though. it's still dry. maybe someone replaced the master cylinder before I got the car, but didn't replace the booster. that would explain the fluid in the booster, yet plenty of bake fluid and a dry M. cyl.

whatever. Thanks