brake booster

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Apr 24, 2003
i'm sure my booster is shot, can anyone tell me how to trouble shoot it, like how to test if the booster is getting vaccum, and if it isn't, where the leak is
1976 Fj40, stock brakes and 2f
If you suspect it's leaking pull the vacuum line off and plug it and see if there is a change in how the engine is running.
You should hear it if its leaking. Unless its leaking REALLY badly It will most likely run worse with the booster disconnected. Disconnect the booster and then plug the port on the manifold and then see what it does. If it runs better, your booster is shot. Go to and their brake booster page and read what they wrote at the top, good troubleshooting info.
should it run better or worse? i'd always thought the 2f ran like sheite all the time :)

i know i'm weak, actually it's more the fact that a vaccum leak will kill the engine (cylinder 5 and 6 i think) that and the shame that my bro's hj45 pulls up harder and straighter with drums, and more weight than my weakling little 40 with disks.

not worried about legality at the moment, it's been sitting there for weeks with a busted back end, and i thought it'd be time to rip into it
Running better or worse kinda depends. If there is a leak in the booster than plugging it should improve things. If there is no leak in the booster you should detect no diff.

Still, I had a 40 some years ago that was running so rich I could pull off a vacuum and it would run like a Banchee with his butt on fire, but that's another story.

Regardless, simply listen for a change in the engine ... if it causes it to idle up or down. Remember, you're not listening for changes with the vacuum line open but rather with it plugged compared to when it's on the booster.
One test I got out of a manual (not landcruiser but it should be applicable to all vacuum assisted brakes).With the engine turned off put your foot firmly on pedal and press down with reasonable force.Keeping your foot on the pedal,start motor.If the booster is ok the pedal should drop a little
any suggestions what to plug it with?
Just stick a bolt in the end of the hose

doing the test of applying force to the brakes, then turning the engine on results in no pedal movement. i know what it should feel like as my bro's hj45 works beutifully.

does anyone know, do you get these things rebuilt, or buy a newie (should i lube before bending over). i gotta get my master re-sleaved too. and before saying X shop does them remember it's a fair old swim from australia, but any victorian places that are resonable would be welcome
I remember some online reading some time ago about a guy replacing his booster with one from some other vehicle but I don't recall which and if his had disks or drums. With some online searching you may find a cheaper option.
Bad religion ,brake boosters usually last a long time so there should be 2nd hand units a plenty.Go private,try the Parts Peddler or the Trading Post.If your lucky you might even get a good master cyl with it.
Most boosters you can buy other than maybe from dealer are rebuilt. If done right nothing the matter with these or if you have yours rebuilt. Theres really only a few parts that wear out, and these are replaced.
Funny I should come across this thread...

I found out I have a bad booster last week (1991 FJ80).

Plug vacuum...engine sounds good = uh oh
Start truck, hit brakes...listen for hiss = uh oh

I also had the joy of losing my master cylinder grommets so I have weak braking and a soft (non-existant) pedal.

I love this :ban: truck!
well i tested it, pulled the hose, ran like s***, backfiring and popping. plugged the hose, ran normal. i adjusted the pedal push rod, now i feel the pedal drop when starting it. i still need a new master cyl, it's spewing fluid out the rear seal. also, another Q. my brakes feel like a light switch (have done for ages) where they go from no retardation to bam almost locked. it's a pain in the ass in the wet.. is this the symptom of a common problem?
I'd say fix the MC. Sure doesn't sound normal.
it's on the list, along with new extractors (can't stand the noise anymore) rebuilt diff, new tie rods, and new rear springs. it's going to be a long year
Rebuild the MC first! Brakes are critical (if you value your life), and a rebuild kit is cheap and easy.
hey, i'm not driving it at the moment, so it'll all get done eventually. with a working handbrake, and it parked in gear i don't think the MC is going to endanger anything but the grass under it :) grass loves brake fluid
Makes a good paint remover, too :D

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