Hissing brake booster
New User
Joined: Jan 2001
Posts: 17
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Hissing brake booster
I have a 96 F250 S/C 4x4 with a 5.8l and auto. When pumping the brake pedal you can hear a hissing sound (vacuum leak?) and also the pedal feels spongy. I have a warranty on the truck so I took it to the dealer and they said that besides the front pads being low, everything else is ok. No vacuum leaks, no leaking brake fluid, etc. They also said that if you sit there pumping the brakes you will hear vacuum. I've had the truck 3 years and don't remember hearing anything like this.
I had a Ranger that also had a hissing brake pedal and a new booster fixed the problem.
Does anyone have an opinion on the hissing brake sound in my F250?
Thanks for any feedback.
Kevin
96 F250 S/C 4X4 5.8l Auto
70 Mach1 351C Auto Shaker Scoop 50K mi.
I had a Ranger that also had a hissing brake pedal and a new booster fixed the problem.
Does anyone have an opinion on the hissing brake sound in my F250?
Thanks for any feedback.
Kevin
96 F250 S/C 4X4 5.8l Auto
70 Mach1 351C Auto Shaker Scoop 50K mi.
Senior User
Joined: Jan 2002
Posts: 335
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From: LeClaire IA
Hissing brake booster
i had a brake booster go out on my ranger way back in the day. the hissing was present until you pumped the brake then it would go away. if you pushed the brake hard enough then the engine would die. a friend of mine had a hissing problem on their 80 something 250 and a booster did not fix it. sorry i could not help more. keep us updated.
Posting Guru
Joined: Jan 2002
Posts: 1,346
Likes: 8
From: Baltimore
Hissing brake booster
[updated:LAST EDITED ON 04-Feb-02 AT 11:59 PM (EST)]A bad brake booster will cause a hard brake pedal. You can disconnect the vacuum hose going to the booster (plug the end of the hose going to the engine). This will simulate a bad booster. Check the rubber hose going to the booster for cracks.
I use a mity vac hand held pump and attach it to the input of the vacuum booster and pull 14 hg of vacuum. If the vacuum holds the booster is probably good. If it won't hold vacuum, the checkvalve could be bad, the rubber diaphram has a leak or the case is cracked.
Also if you place your foot on the brake pedal when you start the car the brake pedal should rise alittle if the booster is good.
If you pump the brake pedal it is normal to hear a swooshing sound but not a hissing noise.
I use a mity vac hand held pump and attach it to the input of the vacuum booster and pull 14 hg of vacuum. If the vacuum holds the booster is probably good. If it won't hold vacuum, the checkvalve could be bad, the rubber diaphram has a leak or the case is cracked.
Also if you place your foot on the brake pedal when you start the car the brake pedal should rise alittle if the booster is good.
If you pump the brake pedal it is normal to hear a swooshing sound but not a hissing noise.
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