panic stop woe's

[IDIoit]

the truck has been running almost flawlessly since my build.
one thing I cant seem to overcome is a panic stop situation.

last week on a short 150 mile drive, I was merging on the freeway.
205 in Tracy.
woman in the fast lane decides she wants to change lanes in a line of merging traffic.
she passes me at a high rate of speed, and I was able to get this freight train in behind her.
as im looking, merging into the middle lane, the ***** slams on her brakes to get behind a big rig
that was in the slow lane.
not uncommon for commies.
but I slammed on the brakes to avoid hitting her, and the pedal went straight to the floor.
had enough resistance that I didn't hit her.
but I grantee she washed her soot covered car after I got infront of her and slowed her roll in 5th with it pinned doing 40 mph

anyways,
ive bleed the hell out of the system, by hand and with a power bleeder.
I am not loosing fluid.
all pads and rotors are good.
reman master and hydroboost installed after the first sign of an issue.
I have a willwood prop valve, and rear disc.
the only thing I havnt looked at is my powersteering pump.

everything worked great for the first year and a half.
and in normal driving conditions, the pedal is nice and firm.

its only on those panic stops I have an issue.
happened in Pismo last month too.

You must be registered for see images attach

 

[Thewespaul]

Pretty pic, is that bonneville? What rear disc did you end up going with?

 

[IDIoit]

Pretty pic, is that bonneville? What rear disc did you end up going with?

I have lugnut 4x4's kit.
running a fsuperduty master.
pic was taken in Pismo Beach, CA

 

[gandalf]

I seem to recall, in the dim and distant past, somebody had problems with weak brakes, and found that his rubber lines, those at each wheel, were a partial cause. The rubber lines themselves were weak, and would bulge when he put the added pressure on them hitting the brakes.

Could that be happening? Have you checked?

Just a thought, since you've done so much work on them already.

 

[Thewespaul]

That’s the kit I was gonna use for the ambulance project but once it started coming together I made the call not to use it, those eldo calipers were just not sufficient for that rig. Rear drums got rebuilt and it stops great with the hydro boost setup. Maybe see if you can source an e350 disc rear?

 

[IDIoit]

I seem to recall, in the dim and distant past, somebody had problems with weak brakes, and found that his rubber lines, those at each wheel, were a partial cause. The rubber lines themselves were weak, and would bulge when he put the added pressure on them hitting the brakes.

Could that be happening? Have you checked?

Just a thought, since you've done so much work on them already.

all stainless braided AN style brake lines from skyjacker.
3 years old...
don't think this is my issue, but hell its worth a look!

 

[icanfixall]

Have you tried bleeding trapped air from the anti lock valve? Or have you bypassed that mess yet? I have "lived" with this panic stop issue for a few years. My guess is the anti lock valve is the problem. Hydroboost will only apply a certain amount of brake line pressure before the peddle goes to the floor. When my peddle goes to the floor the truck seems to grab well but release and then your in for a ride till to stop or contact something. There is just not enough time to let off the peddle and re apply the brakes.. Hope this explains what you need to know.

 

[IDIoit]

Have you tried bleeding trapped air from the anti lock valve? Or have you bypassed that mess yet? I have "lived" with this panic stop issue for a few years. My guess is the anti lock valve is the problem. Hydroboost will only apply a certain amount of brake line pressure before the peddle goes to the floor. When my peddle goes to the floor the truck seems to grab well but release and then your in for a ride till to stop or contact something. There is just not enough time to let off the peddle and re apply the brakes.. Hope this explains what you need to know.

all stock RABS junk has been deleted.
I have a willwood adjustable proportioning valve.
adjusted to where I have 4 wheel lock up in the sand at 40 mph.
new brake lines of both the hard and flex state.

 

[FordIDIot]

Scrap that antilock valve for a super duty replacement line. Second check rear shoe adjustment. Three, check master

 

[IDIoit]

Scrap that antilock valve for a super duty replacement line. Second check rear shoe adjustment. Three, check master

third time mentioned....

RABS HAS BEEN DELETED.


I AM RUNNING REAR DISC BRAKES.
no pad adjustment

new master installed and symptoms reoccur

 

[Clb]

Ummm
Rabs????

Only thing I have is, power steering pump not keeping up or the air chamber in the hydro unit weak.
I recall one with a Schrader valve installed I think to boost the preload or something....

Even with small calipers this should not sink the pedal.
Of course I could be wrong on that one.
Gunna be a ****** if a y.o. hydro is bad.

 

[IDIoit]

hydro unit is on warranty. so im good there lol

 

[no mufflers]

so if you pump the pedal several times does it get stiffer?

 

[IDIoit]

so if you pump the pedal several times does it get stiffer?

always feels the same, until I slam it hard. I thought the master was leaking internally, that's why I replaced it.
guess it could be a crappy new master?
just don't get how it would just go to the floor in a panic situation

 

[no mufflers]

we could rule out air in the system then, right?

you could try another master and see what happens.

you could also install pressure gauges in line, maybe it would give you some info. have you tried adjusting the proportion valve? maybe to isolate the front and rear.