Really need some help with my brakes

[tara]

hi,

after installing disc conversion kit, new 7 booster dual, new MC, proportioning valve, new rear drum brakes. braking sucks !!!! WTF

i m trying to describe the problems :

- braking is weak and i have really to push super hard on pedal to make it stop

- the pedal don't return at its place fast so it continues braking even when i stop pushing the pedal

i have noticed that brake fluid pressure is strong for the discs calipers but super weak at the rear cylinders.

whats wrong, honestly i don't understand.

thanks for your help

[Curly]

The problem is most likely in the proportioning valve. Did you replace with a stock unit or an aftermarket adjustable one?
Curly

[Stuka]

How did you bleed the brakes, and did you bench bleed the master cylinder?

[tara]

The problem is most likely in the proportioning valve. Did you replace with a stock unit or an aftermarket adjustable one?
Curly

this model

https://www.tomsbroncoparts.com/pages/w ... iagram.jpg

[tara]

How did you bleed the brakes, and did you bench bleed the master cylinder?

not bench bleed, but it doesnt look that my issue could be cause by a bad MC

[Cheap Hobby]

Dose the new proportioning valve need to be Bled? Did the new Mc come with a new vacuum hose fitting or did you reuse the old one ? Had an old one that was reused fit tight when installed but did not seal well with the new grommet.

[tara]

Dose the new proportioning valve need to be Bled? Did the new Mc come with a new vacuum hose fitting or did you reuse the old one ? Had an old one that was reused fit tight when installed but did not seal well with the new grommet.

i don't know about bleeding the proportioning valve, but yes we reuse the old vaccum seal

[Stuka]

How did you bleed the brakes, and did you bench bleed the master cylinder?

not bench bleed, but it doesnt look that my issue could be cause by a bad MC

If you did not bench bleed the MC, its going to be very difficult to get the brakes to work. I HIGHLY suggest you do this. You can't get all the air out in the vehicle as the plunger wont be compressed in far enough.

[Curly]

The problem is most likely in the proportioning valve. Did you replace with a stock unit or an aftermarket adjustable one?
Curly

this model

https://www.tomsbroncoparts.com/pages/w ... iagram.jpg

Link doesn't work. Most prop. Valves have a pin that must be lifted and held out of the way during bleeding. Personally, I've never had to do it but it might be your problem.

[Stuka]

The problem is most likely in the proportioning valve. Did you replace with a stock unit or an aftermarket adjustable one?
Curly

this model

https://www.tomsbroncoparts.com/pages/w ... iagram.jpg

Link doesn't work. Most prop. Valves have a pin that must be lifted and held out of the way during bleeding. Personally, I've never had to do it but it might be your problem.

Yeah, I have never had to do it either, but it may be because I use a vacuum bleeder.

[letank]

There are 2 types of proportionning valve push or pull.

The 74 has a push style and a use a gig to hold the pin down, but after a few times, I did not use the holding gig, and the bleeding worked well. In fact you can use the one man brake purge as seen here -commenté en français- I was helping a friend... in 2009... and yes it is the rear brake cylinder of the 74...

https://www.youtube.com/watch?v=LAg5b1ulmIk

forgot to add that all is needed is to depress brake pedal, but but a small block of wood under the pedal to prevent pushing the pedal to the metal.

[tara]

The problem is most likely in the proportioning valve. Did you replace with a stock unit or an aftermarket adjustable one?
Curly

this model

https://www.tomsbroncoparts.com/pages/w ... iagram.jpg

Link doesn't work. Most prop. Valves have a pin that must be lifted and held out of the way during bleeding. Personally, I've never had to do it but it might be your problem.

http://www.ebay.com/itm/gm-style-propor ... 35e5529ad9

[tara]

i dont have this tool, so i guess, i might have air in the prop valve

http://www.ebay.com/itm/Proportioning-V ... 0584863504

or it is the pin holder which as to be used ? like this http://www.fordification.com/forum/view ... hp?t=45503

[tara]

i m little bit lost : i thought that the best way to bleed the system was with two persons : one is pressing the pedal and the other is opening and closing the bleeders on brake : the farthest first and finish with the closest

[44bz]

i m little bit lost : i thought that the best way to bleed the system was with two persons : one is pressing the pedal and the other is opening and closing the bleeders on brake : the farthest first and finish with the closest

Or get a vacuum pump to pull the air out thru each cylinder or caliper. When I did my disc brake/booster swap I only bled the MC before installing, then bled the lines. I never bled the prop valve on its own.


Sent from my iPhone using Tapatalk

[tara]

i m little bit lost : i thought that the best way to bleed the system was with two persons : one is pressing the pedal and the other is opening and closing the bleeders on brake : the farthest first and finish with the closest

Or get a vacuum pump to pull the air out thru each cylinder or caliper. When I did my disc brake/booster swap I only bled the MC before installing, then bled the lines. I never bled the prop valve on its own.


Sent from my iPhone using Tapatalk

using a pump is superior to the classic method using the pedal ?
do i have to bleed in the same order ? farthest first ?

[tara]

but the weird thing is not only that braking is weak and i have really to push super hard on pedal to make it stop , but that the pedal don't return at its place fast so it continues braking even when i stop pressing the pedal (the rear drums were still very hot 30 minutes after parking the car home, and the front disc were cold)

[letank]

using a pump is superior to the classic method using the pedal ?
do i have to bleed in the same order ? farthest first ?

Not really superior, but it is a lot easier to use vacuum to prevent snafus...

In the video that refered a few posts above, the vacuum pump did not work, the electric vacuum pump did not work, so I had to use the one man bleed process with a hose connected to the purge of the rear cylinder, the other end submerged in brake fluid. I had to push hard, but after the 3 press, the line cleared up.

If the pedal is not returning then you have a problem... of valve being sticky -not an expert, but it could be either the MC of the prop... but someone with more experience will respond...

[tara]

my mechanic said that the booster is too small and my engine doesn't produce enough vacuum level to support the dual booster.

[Curly]

I found this on a Ford (gasp!) forum. This guy may be right.
Quote: Your Pedal check valves are damaged.

Get a NEW booster. Warranty replacement or some such.

Power brake sluggish return is almost always the relief valve built into the sealing ring at the plunger input failing to let in fresh air and you're fighting a vacuum from the other side.

It allows the diaphragm spring to overcome the engine vacuum and return the brake pedal to the normal position.

it is NOT a problem with your calipers or drums.

Think of it like this, if you push the pedal it the air ruses out of teh booster diaphragm into the engine (the engine is actually helping you push) then when you let it go, the engine is still sucking and the spring is trying to push AIR trapped on the pedal side of the booster back out so it can return to normal position. Therein lies your problem, the BACK of the booster diaphragm is not allowing air back out thus causing your slow return of pedal and brake dragging./quote

Found it here: (post #3) http://www.fordmuscleforums.com/fairlan ... eturn.html
He suggests cracking both lines at the Master Cylinder and trying the brake. If the problem is gone, then the problem is in the lines/prop valve/calipers.

Curly