Should a brake booster hold a vacuum?

[Alvin in AZ]

I've got 4 brake boosters (4 trucks and only one -sorta- holds a vacuum.
What's the deal?
Does something have to be moved inside of it to get it to seal or what?

I tried pumping them up with a hand vacuum pump tester.
One pumped up one time, I put the brakes on, then it wouldn't pump up again.

Alvin in AZ

 

[1985 Ford F-150]

What condition are your lines in?

 

[Alvin in AZ]

What condition are your lines in?

The brakes work good!
('75 F150 360FE T18 power front disk brakes)

The vacuum valve on the booster is good too.
All the hoses tested good, I use fuel hose for vacuum lines.
3/16" fuel hose is the one to find.

I was looking for a vacuum leak and tested the brake booster while I was at it.

Turns out the "can of tomatoes" was leaking again. :/
I'm in the process of replacing it with the plastic ball off the '90 F250 parts truck.

Anybody ever take a brake booster apart?
Before I turn this one in for the core, it's coming apart.

What's going on with it?
It seems like it's wide open, vacuum wise.
Is it supposed to be?

Alvin in AZ

 

[UNRULEE]

I would have to say that if it doesn't hold vacuum that it's bad. It should make the engine run like there is a vacuum leak, because there is!

 

[Mil1ion]

 

[Alvin in AZ]

I would have to say that if it doesn't hold vacuum that it's
bad. It should make the engine run like there is a vacuum
leak, because there is!

LOL

That's the conclusion I came to last night after reading your post.
I got out some other older vehicle service manuals and other stuff.
The '67 Dodge Service manual showed how to rebuild 3 different
types they used in their cars that year. LOL

The dangged things have quite a few parts inside I never thought
about before and each one involves sealing and/or breaking a seal.

I figure there's a bunch of leaky suckers out there just like mine.
They don't leak bad enough to not work, but they still leak tho. :/

I'm going to experiment today and see what I can figure out about
'em and will post anything worth repeating right here.

Alvin in AZ
ps- Thanks Dennis, but I already read that in my '75 FTSM.

 

[Mil1ion]

From what I understand you need the the proper equipment to break them apart as they are spring loaded and can knock you out if not done with this special tool

 

[Alvin in AZ]

From what I understand you need the the proper {Ok, I'll make sure I
have my pinkie out too ;} equipment to break them apart as they are
spring loaded and can knock you out if not done with this special tool

Thanks Dennis, I'll be careful but the spring is a large diameter and I don't
buy it being all that dangerous. And Dodge didn't mention the spring being
dangerous either, but -it was- a '67 book and they didn't have to tell you
sissy/CYA stuff like that back then.

What's happen to us?

Anyway, the trick to using a little vacuum hand pump to test a booster is
to run the vehicle, then discount the booster's hose at the intake manifold
and then pump it down from there. Pump it to what it'll suck down too and
leave it set for a while then check the number, the two I've got on running
vehicles stayed right where I'd left 'em.

Alvin in AZ

 

[fordrka1975]

the booster should hold some vacuum, the nipple the hose hooks to is a check valve. Take it out and you should only be able to blow through it one way. Do you hear any vacuum leaks when holding the brakes? If so you may have a bad diaphram in the booster, Randy.