Do brake boosters fail?

[Rich 89 Gr. Wag]

Since I don't have any fluid leaks, my brakes are spongy, and I'm getting a brake warning light, I'll replace the master cylinder. Should I worry about the brake booster that the master cylinder attaches to? Do those things ever go out?

[Brin M.]

Rare, but it happens. When you have the master cyl off you can check it by taking off the rubber gasket that slips over the push rod and looking inside for brake fluid. Generally when they go bad they suck BF out of the MC until it fills up and leaks down the carpet inside your cab. Make sure the rubber gasket is lined up good when you put the MC on, it's easy to get it cocked and slice a nice gash in it, make s a real nice vacuum leak if you need one. redface.gif

[mandoneer]

if you have a vacuum pump or brake bleeder pump you can apply vacuum to the booster and if it holds vacuum it is prolly good but if it dont its prolly bad . I use probably because there are exeptions to all rules - I have one that holds vacuum and dont work and I have seen some that dont hold vacuum well but work fine

[LRRH]

a surprisingly common cause is the vaccuum hose that runs to the brake booster. even though it may look good....it could be leaking. try replacing the hose and check for improvement.

[Jlamb]

Disconnect the vaccum hose on the booster. With the engine running does the brake pedal still sink? You have to push really really hard. If it does not sink you don't need the booster.

You may just have some air in the lines, or a leak some where. Did you peak under the vehicle to see if you could see any leaks out of the corners?

Do an isolation test. Take some non aggresive hose clamps (kinda like vice grips with smooth edges), clamp of one of front brake line, and press on the brake does the pedal sink? if it still does go to the other side and repeat. If not you have found the problemed brake component and more than likely it is the caliper. When the clamp is on the front lines and the pedal still sinks go to the rear brake line and clamp it off. Agian does the pedal sink? if it does it is probably a master cylinder. If it does not sink you probably need to replace the wheel cylinders. When I say clamp the lines, I am saying to clamp off the rubber lines.

Hope it help

[89grand]

When the booster goes bad you'll have a big time vaccuum leak. It should be obvious because your Jeep will run like sheeeit. Plus the pedal will feel like a rock, real hard to push.

I doubt the booster is your problem, it wouldn't make the brake light come on, the booster just makes the pedal easier to push. You got a master cylinder problem of some kind.

[The Anti-Chrysler]

Yes there's no way the booster can make the light come on. The warning switch is in the combination valve, which will go off under a loss of fluid pressure. You probably have a master problem or a leak somewhere. Check your rear wheel cylinders if you haven't already. There might be a small leak that isn't making it to where it would be visible.

[Ernzo]

When my booster went out, the first thing I noticed was the brakes acted like there was not power assist. There was a loud hisssss from under the dash when I aplied them.
Replacement was real fun....

[carrotman]

My 76 has a plastic check valve on the vacuum hose to the booster that can go bad. But if the brake light is on you probably have a leak. The brake line on the rear axle can rust out because salt spray stays there.

[JAllenWAG]

Check proportioning valve and wheel cylinders. If they are leaking the light will come on.

[SHOOTER6]

ERNZO, my brake booster went out about a month & a half ago, made the same noise. I replaced it & my brakes work fine now. I'll look in my records for where I got the new one, I paid around 60.00 U.S. The new one was bare metal so I taped it off and painted it black. Mine came without the master cylinder. I just unbolted the master cylinder from the booster leaveing the lines connected. Then I replaced the booster finishing up with reattaching the master cylinder. I didnt half to bleed my brakes though its a good idea to do it anyway. I'm waiting for my lift..

P.S its way easier if you have a second set of hands & expect to get bloody knuckles because the nuts/studs under the dash are in hard to get areas.A wobble extention for your ratchet & a racheting flex head wrench help too..

[Ernzo]

Originally posted by SHOOTER6:

P.S its way easier if you have a second set of hands & expect to get bloody knuckles because the nuts/studs under the dash are in hard to get areas.A wobble extention for your ratchet & a racheting flex head wrench help too..Indeed!! The nuts that held mine in place under the dash were like toy nuts, the one Tonka uses! I ended up have to actually cut one of mine off!! (nuts)(under the dash)

[ February 04, 2004, 08:49 AM: Message edited by: Ernzo ]