'93 Pedal to floor, brakes 'farting' AFTER stopping

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'93 Pedal to floor, brakes 'farting' AFTER stopping

Postby DeeJay » Wed Mar 25, 2015 5:38 pm

I searched around the internet and didn't find anything conclusive, and here there is a couple minutes enforced between searches... So couldn't search much here.

Months ago, after stopping at the light, the pedal would slowly sink down a bit. Lifting up and reapplying the brake would correct it. When it would sink, it was like the effective distance I pressed was lowered. If I pressed lightly from the start, the car would drift when it sinks, but when applying normal pressure or more, the pedal would lower without effecting braking.

Eventually breaking took pressing the brake lower and lower. Occasionally the brakes would 'fart' - A loud 'farting' noise and the brake would pulsate rapidly. The pedal would also become firmer and it would stop faster/sudden. I took the wheels off and the pads had plenty of 'meat' still. Previous owner lost the tool for the security lug on one back tire, so I didn't try bleeding the brakes (I heard its only effective if you do all four). Having carpal tunnel syndrome, I have put off grinding the lug down to fit a Bolt-Out over it. A couple times it made the sound AFTER stopping, and the ABS light blinks briefly. The last time I drove it, I noticed it slightly drifting to the right when braking.

Engine off or on, there is more 'woosh' sound than I remember as normal when pressing the brake. After releasing the brake it takes 2 to 4 seconds for the brake pedal to return to its resting position, with it taking longer with the engine off. A loud 'woosh' (and a probably normal squeaking) accompanies it.

With the engine off, pressing the brake has much more resistance than when on, but still much less than other vehicles when they are off. Pumping makes the pedal _softer_. I noticed a fast press has little resistance, and a slow one has more resistance. Likewise when I was driving it, gradual braking was no problem, but applying the brake quickly (even if only partially) would cause it to drop to 1/2" from the floor and have little braking power.

Holding the pedal at halfway while the engine is off, when I start the engine the pressed pedal drops to the floor. Pumping makes it alternate between just as soft/low and being harder/higher. No consistency.

Pressing the pedal while the engine is on, it goes to the floor with anything other than very light pressure. When I turn the engine off, it slowly pushes my foot back to the top.

I need to make the car drivable again, but can't figure out what the problem is. With carpal tunnel syndrome limiting the amount of work I can do and limited finances preventing "throw parts at it" type troubleshooting, I can't figure out what to test/replace first.

I know I need to get the lug off... Anyone know anything easier (on wrists) than cutting with a Dremel until I can fit a Bolt-Out socket over it?

Thanks for reading.

Edit: Duh! I forgot the make and model. It is a 1993 Pontiac Bonneville SE. It was over 250k miles when I got it, and all the plastic in the cabin was brittle and falling apart.
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Re: '93 Pedal to floor, brakes 'farting' AFTER stopping

Postby marco_1978_spyder » Fri Mar 27, 2015 8:02 am

You may have come here thinking "H body" was referring to your car. Your car may be an H body since GM re-used the platform name many years later.

Read the header here again...Your on a forum about a totally different H body.
Not that the nice hot-rod folks here, aren't willing to help you. But I think you'll get more bang for your time on a more relevant forum, to your '93 bonneville.

After finding your pad's were ok. did you check the fluid? what did you find. Sounds like a bad master cyl. triggering the ABS to go into emergency stop mode.
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Re: '93 Pedal to floor, brakes 'farting' AFTER stopping

Postby Monza Harry » Fri Mar 27, 2015 11:22 pm

marco_1978_spyder wrote: Sounds like a bad master cyl.

I'll 2nd that! At least part of/related to the problem! Harry
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Re: '93 Pedal to floor, brakes 'farting' AFTER stopping

Postby gerbsinmd » Sat Mar 28, 2015 11:39 am

Had almost exactly the same symptoms on my 97 Blazer - it was actually the brake booster that was the problem. The woosh and farting sounds are the give away.
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Re: '93 Pedal to floor, brakes 'farting' AFTER stopping

Postby Monza Harry » Sat Mar 28, 2015 2:19 pm

gerbsinmd wrote: the brake booster that was the problem. The woosh and farting sounds are the give away.

So that would seem that my wife was right about "something being wrong with me"! It would indicate that I must need a brake booster, but I am afraid to ask the doctor for a new brake booster! In all seriousness that is GOOD to know, but isn't the rod through the booster solid? So how does the pedal go to the floor with out the MC bypassing or a leak? Harry
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Re: '93 Pedal to floor, brakes 'farting' AFTER stopping

Postby Kenova » Sat Mar 28, 2015 4:49 pm

Most likely a ripped diaphragm.


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