Brake booster problem?
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Senior User
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Brake booster problem?
Usually when I have a brake booster failure I can hear air inside the cab when i depress the pedal. Has anyone else had one fail and not hear the woosh sound when you depress the pedal?
Moderator
Joined: Jan 2004
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From: SW Va
I personally have never had a brake boster fail.
I have heard folks say that they've had them fail & suck brake fluid out of the brake master cylinder, but I don't remember anyone mentioning anything about hearing noise in the cab, coming from them.
Do you suspect yours has failed, because you have to push harder than normal on the brake pedal to stop, or are noticing the brake master cylinder fluid level dropping & can't find the leak?????
I have heard folks say that they've had them fail & suck brake fluid out of the brake master cylinder, but I don't remember anyone mentioning anything about hearing noise in the cab, coming from them.
Do you suspect yours has failed, because you have to push harder than normal on the brake pedal to stop, or are noticing the brake master cylinder fluid level dropping & can't find the leak?????
New User
Joined: Apr 2007
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Brake booster
I have noticed on my '85 ranger air hissing from where the rod goes through the firewall into the booster. It stops when I apply the brakes. I don't know if they are related but I just had to replace a failed master cylinder. I can still hear the air, but not nearly as bad.
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Joined: Jan 2004
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From: SW Va
If you hear a "hiss" coming from around that area, you likely have a vacuum leak in the brake boosters diaphragm.
You could test that thought out, by removing & plugging the brake bosters vacuum line, then start the engine & listen in that area again, for the hiss. If it's gone, you have a leaking brake booster & should rplace it imo.
If it's still there, something else is wrong.
You could then use a piece of hose or tubng, as a flexable stethoscope to listen around & perhaps find the problem, or at least isolate the hiss ara.
You could test that thought out, by removing & plugging the brake bosters vacuum line, then start the engine & listen in that area again, for the hiss. If it's gone, you have a leaking brake booster & should rplace it imo.
If it's still there, something else is wrong.
You could then use a piece of hose or tubng, as a flexable stethoscope to listen around & perhaps find the problem, or at least isolate the hiss ara.
Elder User
Joined: Jul 2005
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A friend of mine once replaced his booster for that reason.. and it didn't fix it. I checked it out for him and found a vacuum "cruise control deactivation" switch mounted to the brake pedal that was leaking.. but if your truck doesn't have that type of thing, then there's really nothing else it can be except the booster.
Good luck.
Good luck.
Moderator
Joined: Jan 2004
Posts: 13,851
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From: SW Va
Ohhhh thats a good one MazdaRangerGuy, I never would have thought of that one, I sorta had the in cabin HIVAC system vacuum control lines, fittings & components in mind, even though they really aren't that close to the brake pedal area.
Anyway 4xFordFeak, let us know what you find.
Anyway 4xFordFeak, let us know what you find.
Last edited by pawpaw; May 26, 2007 at 12:29 AM. Reason: omitted a word
