How should a power brake booster be tested?

[robroy]

Hello Folks,

Is it possible to test a power brake booster after it has been removed from the truck?

I removed mine today and would rather not go to the bother of re-installing it if it's bad or marginal. It's about twelve years old and looks pretty nasty, but looks aren't everything.

Thanks very much!
-Robroy

[FORDification]

If you've got a vacuum pump, you can just hook it up and get some suction on the hose and let it set for a few, to see if it'll hold vacuum. If it does, then the diaphragm is good. That's about the only way I'm aware of. If the vacuum level drops or you hear any hissing inside, then the diaphragm is leaking and the booster should be replaced.

[Hawkrod]

You do have to have a MC on it to test for vacuum. Also, this off the vehicle test will only tell you if it sealing inside not if it actually works. Power boosters have an internal valve to make them work and the only way to test is by stepping on the pedal. They may hold air fine until you step on the pedal. Hawkrod

[FORDification]

Here's a couple links to read:

http://www.hemmings.com/mus/stories/200 ... ure24.html
http://www.roadkillcustoms.com/hot-rods ... r-test.asp

[robroy]

Keith and Hawkrod, thanks for your replies!

Keith, I'll read those links in detail--thanks.

This question may not have a good, single answer, but about how long should a vacuum brake booster last?

Thanks again!
-Robroy

[Jake11]

Heres my 2cents.
If you got doubts about it for some reason, get a new or rebuilt one.
Jake

[ToughOldFord]

You do have to have a MC on it to test for vacuum. Also, this off the vehicle test will only tell you if it sealing inside not if it actually works. Power boosters have an internal valve to make them work and the only way to test is by stepping on the pedal. They may hold air fine until you step on the pedal. Hawkrod

This is true. IE the booster in my Jeep holds a vacuum fine, until I depress the pedal. Then it leaks so bad you can hear it with the engine running.

[robroy]

Hi Jake and ToughOldFord,

Jake, you're probably right about just replacing it and not worrying about it. Even if the old one is still working, it's got a good number of years on it and this is a very easy time to pop a new one in.

Knowing that a master cylinder needs to be installed to properly test it makes me even more inclined to put in a new one and forget about it.

Thanks guys!
-Robroy