brake pedal goes PSHHH before starts braking

MIGHTYMOUSE

MIGHTYMOUSE

Turbo F body guy
i have this like 2" of brake pedal travel i have to push through before the truck begins stopping.

its very unnerving due to the fact that there is some delay while trying to press through it.

it only does it when the truck is running, brakes firm up good when truck is off.

i just did the abs delete and it made no change in this sound or in my braking response time. I would love to mount these f body calipers and rotors i have but i need somebody to be selling the kit!!

please tell me i am not the first with this.
 
91blazins10

91blazins10

Active member
Re: brake pedal goes PSHHH before starts braking

The lines may need to bled more or your brake booster has a leak. :2cents:
 
mattw

mattw

Active member
Re: brake pedal goes PSHHH before starts braking

Sounds like a good time to move to hydroboost.. Go visit your local u-pull-it yard and get all of the lines and everything from an astrovan..


-Matt
 
Loeryder

Loeryder

New member
Re: brake pedal goes PSHHH before starts braking

Brake booster not holding vacuum?

If you get the duck quack noise it is the check valve that the line from the upper intake connects to.

If you have a dead pedal feel it is more than likely the booster.

Did you have this before the ABS delete?
I would do another bleed since you had it all opened up doing the delete.
 
George Blake

George Blake

DONATING MEMBER
Re: brake pedal goes PSHHH before starts braking

Mine used to do this and then stopped suddenly and I got a hard pedal now and not as much assist. I've narrowed mine down to the power brake booster. The master cylinder swap did nothing in my case.
Now there is also a "duck call" as I call it. That is caused by the leaking power brake booster check valve.
 
4C FED

4C FED

Absolutum Dominium
Re: brake pedal goes PSHHH before starts braking

Mine has started to do it as well after ABS delete & one good panic stop.
Intermittently, when I'm at a stop the truck will start to roll & I'll have to pump the pedal to stop the roll.
I'm sure I just need to re-bleed & it will be good.
Mighty-vac blows for brake bleeding IMO. Draws to much air around threads on bleed nipple.
 
Loeryder

Loeryder

New member
Re: brake pedal goes PSHHH before starts braking

I have found when using the mity-vac to bleed brakes I use one of the "needle" ends on the vac hose and stick it INTO the bleeder.

Do not just push the hose end onto the bleeder.
It doesn't seal for shit.

And FWIW, I bled almost an entire bottle of new fluid to make sure I pushed all the old out and guarantee I had no bubbles.
Did corner to corner 3 full times before I was happy with it.
RR, LR, RF, LF you bleed from furthest away from master cyl to closest (Especially after opening the system).
 
4C FED

4C FED

Absolutum Dominium
Re: brake pedal goes PSHHH before starts braking

I bled mine in the same sequence.
I used a piece of silicone hose to seal around the nipple & put grease around the threads on the nipple to help seal air out. Still seems to draw to much outside air from around the threads on the nipple.

I'm going to toss it and get one of those pressure bleeders that attaches to the reservoir. Seems to be much more efficient.
 
Loeryder

Loeryder

New member
Re: brake pedal goes PSHHH before starts braking

4C FED said:
I bled mine in the same sequence.
I used a piece of silicone hose to seal around the nipple & put grease around the threads on the nipple to help seal air out. Still seems to draw to much outside air from around the threads on the nipple.

I'm going to toss it and get one of those pressure bleeders that attaches to the reservoir. Seems to be much more efficient.
Click to expand...
If you decide to "toss it" please do so into a decent cardboard box with my name and addy on it. At the very least I will save it for spare parts. :tup:

Like I said, I am fairly happy with mine when using those black "needle" adapters to seal on the inside of the bleeder.
I do still use a 2nd person to pump the brakes but it goes much quicker with vacuum on the bleeder.
 
4C FED

4C FED

Absolutum Dominium
Re: brake pedal goes PSHHH before starts braking

Loeryder said:
If you decide to "toss it" please do so into a decent cardboard box with my name and addy on it. At the very least I will save it for spare parts. :tup:
Click to expand...

I've got 2 of them and I'll be more than happy to send them both to you.
PM name & addy to me.
 
MIGHTYMOUSE

MIGHTYMOUSE

Turbo F body guy
Re: brake pedal goes PSHHH before starts braking

my brakes had this symptom before the delete. that is why i did the mod.
the brakes are bad enough without having to wait for them to start doing anything!

on the booster. i can let the truck sit overnight and go out in the morning and pop the manifold line off of it and 'break the seal' and hear it leak down so its not that.

its free to bleed some more i guess.. just time.

i'll look up master cylinder 'bypassing' sounds like a good lead.
 
Flyin Ryan

Flyin Ryan

hated cuz he drives fords
Re: brake pedal goes PSHHH before starts braking

I know when I deleted my pos abs module it took me a good four or five times bleeding the entire system before my brakes were back to 100%

I'd say bleed em some more if you have the time
 
Xtrempickup

Xtrempickup

All turbo All the time
Re: brake pedal goes PSHHH before starts braking

mine seems to qwakk a little, how do you fix it. it stops fine tho, but let off the pedal you can hear it
 
Loeryder

Loeryder

New member
Re: brake pedal goes PSHHH before starts braking

Xtrempickup said:
mine seems to qwakk a little, how do you fix it. it stops fine tho, but let off the pedal you can hear it
Click to expand...
replace the brake booster check valve

duck quack noise = faulty check valve.

get one from GM not the HELP crap at autozone.
I have tried 2 of those and neither fits like the stocker.
 
B

Bad Ass Black Trucks

New member
Re: brake pedal goes PSHHH before starts braking

91blazins10 said:
The lines may need to bled more or your brake booster has a leak. :2cents:
Click to expand...

Agreed. If you idle drops significantly when you hit the brakes it is most likely a vacuum leak.
 
4C FED

4C FED

Absolutum Dominium
Re: brake pedal goes PSHHH before starts braking

DaveP6999 said:
How many of you use the 'clip' thing to hold in the pin on the end of the proportioning / combination valve??? I thought so. No one.

It is REALLY difficult to get a good bleed without using one of these. The fronts just WON'T bleed easially without it. I'll post a pic, if there's any interest. The clip thing is available at NAPA. About $9.00.
Click to expand...

Post up. I've never heard of or seen this clip before.
 
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