Not the braking I want

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schmitt

schmitt

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Hey guys,

Put a brand new master and power booster on my rig hoping for great brakes. Not getting the brakes I want.

Front disc rear drum. Mustang 2 front end.

When just hitting the pedal ever so slight I'm getting the dreaded sqweel. Adjusted the booster rod so it's not pressing on the master. Doesn't seem to have drag when spinning the wheels when brakes not applied. Just cruising they feel pretty good besides that squeal every so often.


Also if trying to power brake the truck wants to push. Need improved front brake calipers and rotors or line lock?

Thanks for any help
 

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Are you running good quality pads? Were they broke in properly? That in of itself can make a huge difference.

I would highly recommend a line lock, more grins than you can imagine. :D
 
Pads where already there. Should I go to a good pad and slotted roter? How about caliper?

Not sure why the truck pushes so bad when trying to power brake.
 
I would try a good pad, and break them in properly. Not sure what kind of proportioning valve you have on it, there might be an issue there too. Maybe it's not getting enough pressure to the front like it should.

How does it stop?
 
It's new if that matters, Seems to stop pretty good. ( haven't fully locked um up)
Won't hold the truck when putting power to it.

I might be getting to much rear brake for the power braking? Should be making plenty of power to just smoke the tires right off . Soon as I would let off the brakes the tires would light.
 
schmitt said:
I might be getting to much rear brake for the power braking? Should be making plenty of power to just smoke the tires right off . Soon as I would let off the brakes the tires would light.
Click to expand...

That's why I was asking about the valve. Maybe an adjustable valve inline to the rear brakes is in order.
 
Just pulled my master and the booster Rod was pushing in on the master some. Not sure enough to to matter but I re adjusted.
 
schmitt said:
Won't hold the truck when putting power to it.
Click to expand...
I need some help understanding this....do you mean that if you press on the brakes, and then mash the throttle, the brakes won't hold it? Are these the stock Mustang II brakes? Was this pulled from the boneyard or what? Is the MC and booster from a Mopar? What rear axle and rear brakes do you have?
 
Starting to make sense. Too much rear brake not enough front brake. slightly applying the brakes lets the front brakes vibrate from not enough pressure. Wont hold the truck because all the braking is going to the power wheels. YUP proportioning valve.
 
You're probably right on the squeal source..... but the pressure on the pads depends on the pedal pressure and the other hydraulic dimensions of the system, and the front pressure will not go up with just a prop valve reducing pressure to the back.

And there may be a lot more to it than that. I hope the OP replies with info. Here's why:

The stock Mustang II front brake rotors are MUCH smaller in diameter than the Mopar A or B rotors. If that is what he has, then the braking torque at the tire contact patch on the front wheel will be something like 25-30% lower for a given line pressure than with the Mopar rotors, or with 11" upgrades to the Mustang II system. So that is why to ask about the whole system and all parts; this may be a seriously under-sized brake setup. But there is no way to tell without clear info.
 
An adjustable proportioning valve will not fix this.

The proportioning valve will only reduce the amount of pressure to the rear brakes, it will not increase the pressure to the front brakes. Adding an adjustable prop valve will just reduce the braking force at the rear, it can not increase it at the front.

Something else is going on. Could be a mismatch in the master cylinder bore size, contaminated or improperly broken in front pads (since they were "already there"), an improperly bled master cylinder (since the push rod was improperly adjusted), or something with the power booster. The brakes should definitely hold the truck, even if they're the smaller MII front disks.
 
Thanks for helping guys!

The front end kit was bought new from JW rod garage to give me coil over suspension on the front end.

It has 11" front rotors

Dana 60 rear with drum brakes.
 
Good lesson on the proportion valve. Always learning. Makes sense. Can't create pressure that does not exist.
 
BG7FR580764
twayne24365 said:
Any pics with this mustang 2 front end in the ol truck?
Click to expand...

image.jpeg
 
Hopefully this reply will stay; they seem to be dissappearing after the new site is up.

Good on the 11" rotors; that is one thing out of the way. So next is to check out the installation for problems. As said, with the pedal rod not right, the bench bleed (which I assume you did) on the MC may not be right and you still have air in the MC. So I would bench bleed.... on the truck.... and the re-bleed everything.

Please give us the info on the MC.

Were the pads those supplied with the kit?
 
nm9stheham said:
Hopefully this reply will stay; they seem to be dissappearing after the new site is up.

Good on the 11" rotors; that is one thing out of the way. So next is to check out the installation for problems. As said, with the pedal rod not right, the bench bleed (which I assume you did) on the MC may not be right and you still have air in the MC. So I would bench bleed.... on the truck.... and the re-bleed everything.

Please give us the info on the MC.

Were the pads those supplied with the kit?
Click to expand...


Yeah I replied to you earlier too.

I did bench bleed the master.

Im going to start over and re-bleed the system like you mentioned being the cylinder was pushed in some. I also picked up some brake lube for the calipers and backside of the pads to maybe get rid of the vibration squeal.

My back brakes are locking up before the fronts I noticed as well, so I ordered a proportioning valve for more adjustability

Pads came with the Gm style calipers. Rotors are 11" Ford Grenada
 
Very cool, friend uses crown Vic front ends in his 68 and 70 f100, I like it!!
 
What is the MC if you don't mind? And is the rear pot going to the front brakes? I can't see from the pix if it has a prop valve with it already, but it almost looks like it. Got a close up pix?

OK, well, I would start with the bench bleed again anyway, sometimes those MC's play heck with getting all the air out. I only do it with the hoses that are open and dump the fluid back in and move the pedal slooooowly in and out.

OK, on the GM calipers. They have bigger pistons and so should result in even more front bias. So the fronts are definitely not working right.

If you have a brand and PN on the pads, let us know. Maybe the coefficient of friction can be found to see how good or bad they are.

The vibration squeal is usually eliminated with shims between the pads and calipers, or sometimes with a rubber-like glue like substance that you smear on the backs of the pads and let it setup a bit. The lube is for any pins and sliding surfaces.

You did clean off the rotors with brake cleaner? Make sure you get some brake cleaner and hose down the pads and calipers to get them cleaned. If the pads got contaminated (like if the rotors did not get fully cleaned), then it may be a challenge to get them properly clean.
 
nm9stheham said:
What is the MC if you don't mind? And is the rear pot going to the front brakes? I can't see from the pix if it has a prop valve with it already, but it almost looks like it. Got a close up pix?

OK, well, I would start with the bench bleed again anyway, sometimes those MC's play heck with getting all the air out. I only do it with the hoses that are open and dump the fluid back in and move the pedal slooooowly in and out.

OK, on the GM calipers. They have bigger pistons and so should result in even more front bias. So the fronts are definitely not working right.

If you have a brand and PN on the pads, let us know. Maybe the coefficient of friction can be found to see how good or bad they are.

The vibration squeal is usually eliminated with shims between the pads and calipers, or sometimes with a rubber-like glue like substance that you smear on the backs of the pads and let it setup a bit. The lube is for any pins and sliding surfaces.

You did clean off the rotors with brake cleaner? Make sure you get some brake cleaner and hose down the pads and calipers to get them cleaned. If the pads got contaminated (like if the rotors did not get fully cleaned), then it may be a challenge to get them properly clean.
Click to expand...

I went around and blead all 4 again and didn't seem to have any air. Didn't re-bleed the master.
 
I went around and blead all 4 again and didn't seem to have any air. Didn't re-bleed the master yet. (Hoping it's not that)

What is the adjustment for the pedal Rod? Alway seem to have a bit different play.
 
Mbm brake parts I used. Master/valve and booster

image.jpeg
 
OK, this is a 1" GM MC, with the front brakes coming from the the FRONT half of the MC, unlike the Mopar where the front brakes come from the rear half of the MC. So please confirm that your front brake lines are coming from the 2 front ports.

Do you have the drum size and brake shoe width of the rear brakes?

If you have not re-bench-bled the MC, then IMHO, you have wasted time. How are you doing the bleeding? I ask because there are techniques that don't work well.

Are the front calipers mounted with the bleeders pointing up?

Is this a GM booster?

And sorry to ask so many simple questions but they are being asked for a reason. There are a lot of things can go wrong and they all have to be checked.
 
nm9stheham said:
OK, this is a 1" GM MC, with the front brakes coming from the the FRONT half of the MC, unlike the Mopar where the front brakes come from the rear half of the MC. So please confirm that your front brake lines are coming from the 2 front ports.

Do you have the drum size and brake shoe width of the rear brakes?

If you have not re-bench-bled the MC, then IMHO, you have wasted time. How are you doing the bleeding? I ask because there are techniques that don't work well.

Are the front calipers mounted with the bleeders pointing up?

Is this a GM booster?

And sorry to ask so many simple questions but they are being asked for a reason. There are a lot of things can go wrong and they all have to be checked.
Click to expand...



I believe my lines are hooked up correctly. I will post a pic. The two lines clamped together are the front lines.

Im not sure on that brake shoe size in the rear.

I didn't bench bleed the master again. When I did it last time I ran hose's from the output holes on the side back into the fluid reservoir they belonged in and slowly pumped the piston until I seen no air in the hose, mounted it to the truck, pulled the hoses quick and hooked up the lines. As far as bleeding the brakes I start from pass rear until no air then driver rear, pass front, driver front.

The front caliper bleeders do face up

MBM set me up with the brake setup. Its there Universal 7" dual diaphragm booster
 
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