Brake help needed

[KBUCK1]

I have a disk brake dana 44 and 11 inch rear drums. Manual master cylinder from 84 ramcharger. All new brake lines including braded stainless lines from frame to axles. I have bled brakes numerous times and Im confident the air is gone. Also, a good friend that used to work in a shop come by and confirmed that they were bled as well.

I have a very soft pedal. I have narrowed the problem down to being in the front. I disconnected the front line from the master cylinder and capped that master cylinder port off and the pedal is rock solid. ( the rears are working great) when I disconnect the rear line from the master cylinder and cap that port the pedal is very soft and nearly goes to the floor. I have confirmed that the calipers are not on backwards and both are new calipers. Also, Im using an H block and not a proportioning valve. Does anyone have a clue what could be going on?

 

[broncnaz]

You need a new master cylinder the seal for the front brakes is leaking so you have no fronts thats why when you plug the rear you get a good pedal and plug the front no pedal.

 

[KBUCK1]

You need a new master cylinder the seal for the front brakes is leaking so you have no fronts thats why when you plug the rear you get a good pedal and plug the front no pedal.

It's a new master. I thought that was the problem too so I bought ianother new one with same problem. When I plug the front brake port off the brake is solid. ( not the front port towards the front of the truck). When I plug the rear brake line port and the front brakes being the only ones operating the pedal is spongy. Also, I plugged both ports on the master at the same time and pedal doesn't budge. I think the master is fine. It's something in the front. Could a caliper cause this?

 

[broncnaz]

Still even new master cylinders can be bad. Kiinda rare that 2 back to back would be bad but it happens.
Although you may want to verfiy the master cylinder bore size. It may be to small for disc brakes. that would be a sign of soft braking action you may need a bore size of 1 1/8' or 1 1/4" to keep the disc brakes happy.

Plugging off the MC and getting a soft pedal for the front still points to a bad MC seal and when you cap off the rear brakes you get a hard pedal indicates the rear seal is working like it should.
You could always try swapping the brake lines on the MC see if it changes anything. If it reacts the same then the MC bore size may be to small for your setup.

 

[DirtDonk]

I would think it's also possible for it to be the calipers are not installed correctly and binding up on their sliders.

Can you post up a pic of the front caliper installations?

Paul

 

[bronconut73]

Is this an OEM Ford set of calipers or is this a Chevy conversion?
If it is the Chevy conversion make sure you have ground the knuckles enough and your calipers bleeder in the highest position. They can look right but still be on the wrong sides.
If it is a Ford set up......I am back at the mc.

 

[KBUCK1]

I would think it's also possible for it to be the calipers are not installed correctly and binding up on their sliders.

Can you post up a pic of the front caliper installations?

Paul

I'll get some pics shortly. I think some are misundertanding my original post. When the port that hooks to the rear brakes is capped and the front brakes are hooked up still the brake pedal is soft. When the front brake line port is capped off and the rear brakes are still hooked up the the pedal is solid. so, i know everything to do with the rears are working and the master cylinder is working on the front brake line port or the pedal wouldnt be hard with that port capped.

the bore size for that master cylinder is 1 1/8

Its a factory ford disk setup on a dana 44

Bleeders are in the highest position

When both ports are capped the pedal will not budge

 

[BRONCROB]

Does it stop?Mine is a tad soft with my F250 MC but stops fine.They probably aren't ever going to be really solid.

 

[73azbronco]

How are your rubber lines on the front?

 

[KBUCK1]

How are your rubber lines on the front?

No rubber. Braided stainless.

Could it be that I'm not using a proportioning valve? Thought about running over to summit to pick up a single in and single out proportioning valve and mount plumb into the rear brake line. It says it's adjustable and reduces up to 57 percent to rear

 

[DirtDonk]

I wouldn't think so. A prop valve is not (supposedly) effecting the front brakes at all. It only reduces fluid pressure to the rear circuit.

A 1.125" piston bore used with the smaller Ford calipers should be good and solid. Even the stock master size can be.
Did this characteristic occur right from the beginning of the conversion? If so, was the entire system done at the same time?
Or have you been driving it with good brakes up to some point?

Paul

 

[KBUCK1]

I wouldn't think so. A prop valve is not (supposedly) effecting the front brakes at all. It only reduces fluid pressure to the rear circuit.

A 1.125" piston bore used with the smaller Ford calipers should be good and solid. Even the stock master size can be.
Did this characteristic occur right from the beginning of the conversion? If so, was the entire system done at the same time?
Or have you been driving it with good brakes up to some point?

Paul

This is not a conversion. Ive owned this 76 for 13 years and have been doing a frame off the last 2 years. I bought all new brake components.(master cylinder, lines, pads, shoes, springs ,cylinders and calipers) I done away with the proportioning valve and used an H block instead. I used the ramcharger master basically because it looked better to me. could they have given me a caliper thats wrong that would bolt up but cause problems?

 

[73azbronco]

Then, my only thought is to bench bleed the master cylinder again, you most likely have air in the system. Don't have to remove the MC to do it, just run the brake line right back into the reservoir.

 

[broncnaz]

Bit confused by the diagnosis. If rear circuit is correct, MC piston will only travel until rear shoes make contact with drum. The point of a dual reservoir MC is that either the front or rear circuit can fail and still have a remaining circuit.

The obstacle becomes balancing these two, independent circuits such that they work together. Becomes a function of rear, wheel cyl swept volume vs. front, caliper piston fill volume. Complicated by biasing pressure/force in favor of the front with the proportioning valve.

Suggest a read of the tech articles here, then do a serch and read thru all the posts detailing exact components to do a disc brake conversion successfully. It's not complicated and been done 100s of times before. Just stick to the plan.

If he is plugging the port to the front brakes and leaving the rear brakes hooked up and still gets a soft pedal then the front portion of the MC is not working simple diagnosis. The plugged front brake port should result in instant hard pedal.
Thats also why I suggested swapping the brake lines and see what happens. Some MC's are built different and have different bore sizes or even fluid volumne differance between the 2 halfs of the MC.
While I agree he should probably reread the tech articles and consider using parts that are known to work. not saying the ramcharger MC cant work but as was said this has been done 100's of times with other parts that are know to work.

 

[73azbronco]

plugging front line port wont result in a hard pedal unless you can get all the air out which you cant because, well, the port is plugged. I still vote a simple bench bleed is needed. Next option is MC is bad.

Is this a new MC, not rebuilt? I have zero faith in rebuilt anything these days.

 

[broncnaz]

This is not a conversion. Ive owned this 76 for 13 years and have been doing a frame off the last 2 years. I bought all new brake components.(master cylinder, lines, pads, shoes, springs ,cylinders and calipers) I done away with the proportioning valve and used an H block instead. I used the ramcharger master basically because it looked better to me. could they have given me a caliper thats wrong that would bolt up but cause problems?

While there are 2 types of ford calipers only one works with the stock type brake lines. You'd know if you had the other type as the 76 lines wouldnt work.
Prop valves dont really make any differance you dont need them unless your rear brakes lock up before the fronts.

Of course in light of even more info you provided there can be other factors new brake pads take some time to wear in then they start grabbing better. Of course if you used some fancy brake pads they may not work good until they get warmed up. Of course then again it could just be the MC the larger bore size will push more fluid volumne but at less pressure so that can affect braking. Going back to the 1in MC the broncos system was designed with may result in better braking.
Also since you've been doing a frame off for the last 2 years it could be possible that your not used to the brakes on the bronco and trying to compare them to whatever else you've been driving.

 

[broncnaz]

plugging front line port wont result in a hard pedal unless you can get all the air out which you cant because, well, the port is plugged. I still vote a simple bench bleed is needed. Next option is MC is bad.

Is this a new MC, not rebuilt? I have zero faith in rebuilt anything these days.

You can bleed the front port easily enough during plugging. I've done it several times with no bleeding. Still even if it had a little air you have no place for the fluid to go so the pedal will be hard pretty much instantly. if the pedal travels any real distance then the seals are bad

 

[KBUCK1]

You can bleed the front port easily enough during plugging. I've done it several times with no bleeding. Still even if it had a little air you have no place for the fluid to go so the pedal will be hard pretty much instantly. if the pedal travels any real distance then the seals are bad

The master actually came with instructions and caps to cap it off instead of the typical bench bleed. The master has no air.

Bronconaz, it's doing the opposite of what you stated. The rears work great and have solid pedal when front brake line port is capped.

The problem isn't that I'm not used to it. I can jack it up and turn the front tires by hand while brake pedal is pressed. It won't stop like it is now. Well, I guess the rears would stop it.

 

[broncnaz]

More semantics than anything were probably losing the info in the translation as thats what I meant. At least i think. lol
At this point since Im confused.:-X You might try this. Open a rear brake bleeder then step on the brake pedal how is the pedal feel? pedal travel? do the fronts lock up?
If so it is probably a volume issue with the larger MC. Your getting more volume to the rears and they are locking up before the front get enough volume to start working. You either need to go back to a smaller MC or put a prop valve back into the system to limit the fluid to the rear. You might even need to do both.

 

[KBUCK1]

More semantics than anything were probably losing the info in the translation as thats what I meant. At least i think. lol
At this point since Im confused.:-X You might try this. Open a rear brake bleeder then step on the brake pedal how is the pedal feel? pedal travel? do the fronts lock up?
If so it is probably a volumne issue with the larger MC. your getting more volumne to the rears and they are locking up before the front get enough volumne to start working. You either need to go back to a smaller MC or put a porp valve back into the system to limit the fluid to the rear.

This is what I was leaning towards. I went and picked up a single in single out valve and going to try it tonight. But as dirt donk said really it should only affect the rears we'll see soon I guess