Getting my *** handed to me.. these damm brakes

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boosted

boosted

Life Needs Air
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I have 4 wheel disk brakes on my barracuda. Big bolt pattern front, ebay disk rear that uses mid 80's Cadillac Eldorado calipers.

I have all new hard lines along with new hoses and calipers. No leaks but I cannot get a steady firm brake pedal. Pump them and they are good. Let it set and you have to pump them again. The master cylinder was new but old. I did not bench bleed it but have bled the system 4 times now. No air to be seen. Could it be a bad master cylinder? I hate to spend the 200 bucks for a new wilwood one if I don't have to.
 
boosted said:
I have 4 wheel disk brakes on my barracuda. Big bolt pattern front, ebay disk rear that uses mid 80's Cadillac Eldorado calipers.

I have all new hard lines along with new hoses and calipers. No leaks but I cannot get a steady firm brake pedal. Pump them and they are good. Let it set and you have to pump them again. The master cylinder was new but old. I did not bench bleed it but have bled the system 4 times now. No air to be seen. Could it be a bad master cylinder? I hate to spend the 200 bucks for a new wilwood one if I don't have to.
Click to expand...

It definitely could be the master cylinder. You might try bench bleeding it before you replace it, but I have gotten a new m/c that had a bad seal that acted the same way.

I like m/c I got from DoctorDiff
Mopar Aluminum Master Cylinder Kit

I run the 15/16” version, looks like it might be out of stock. They standard 1 1/32 is available.
 
Do rear calipers have e-brake as part of caliper? If so they need to be cycled to bring pads out. Adjusting is a better term. Pins on back of brake pads need to align with notches in piston.
 
You need to bench bleed the master first. You can bleed your brakes a hundred times and unless you bench bleed you’ll have problems. What method do use when bleeding the brakes at each corner? Start with the furthest from the master first
 
Yes it has the ebrake setup on it but not used. I did ratchet the calipers by removing the spring and pushing the leaver forward and backward to ratchet the piston out. When I hit the pedal in the car I here a squish sound from under the dash.
 
4mulas said:
You need to bench bleed the master first. You can bleed your brakes a hundred times and unless you bench bleed you’ll have problems. What method do use when bleeding the brakes at each corner? Start with the furthest from the master first
Click to expand...
Back passenger, driver rear passenger front the drivers front.
 
72bluNblu said:
It definitely could be the master cylinder. You might try bench bleeding it before you replace it, but I have gotten a new m/c that had a bad seal that acted the same way.

I like m/c I got from DoctorDiff
Mopar Aluminum Master Cylinder Kit

I run the 15/16” version, looks like it might be out of stock. They standard 1 1/32 is available.
Click to expand...
That looks like the one I got with my hemi offset plate.
 
The master cylinder must (MUST) be bench bled.
 
mopar head said:
You can bench bleed in the car
Click to expand...
I heard you could not do this as the pedal rod may not fully seat inside the mc.

I have no idea if this is accurate, but I need to bleed a completely new brake system and I'm reading all kinds of opinions, from bench bleed out of the car, in the car, open all calipers/cylinders and let gravity fill the system first, to force fluid from the calipers/cylinders side into the system as air rises.
 
You can bench bleed it in the car, but the M/C must be level.
 
matthon said:
I heard you could not do this as the pedal rod may not fully seat inside the mc.
Click to expand...

I haven't heard that before. I "think" I may have installed my pushrod before installing the master cylinder, but I can't be sure. Not sure why the rod wouldn't go all the in until the retainer seats.

All you're trying to do replace the air with fluid. Here's a picture from when I did mine about 8 years ago. I bought the little kit from a parts store. Fill the reservoir with fuild and pump 2 inches about 20 times.
IMG_20150603_151629.jpg
 
66fyssh said:
I haven't heard that before. I "think" I may have installed my pushrod before installing the master cylinder, but I can't be sure. Not sure why the rod wouldn't go all the in until the retainer seats.

All you're trying to do replace the air with fluid. Here's a picture from when I did mine about 8 years ago. I bought the little kit from a parts store. Fill the reservoir with fuild and pump 2 inches about 20 times.
View attachment 1715924964
Click to expand...
Yeah, and some masters skip the hoses and just give ya plugs to block off the ports...
Hey, if it works, who am I to argue?:)
 
boosted said:
Yes it has the ebrake setup on it but not used. I did ratchet the calipers by removing the spring and pushing the leaver forward and backward to ratchet the piston out. When I hit the pedal in the car I here a squish sound from under the dash.
Click to expand...
When you activate lever does it grab rotor? It should.
 
Yup, I have a similar kit to bleed the mc, should work no problemo.
 
Are your calipers mounted correctly ? Bleeders up ..... I went thru this once and had multiple shops try to bleed them to no avail... My Mopar guru buddy took one look at them and said "your calipers are on backwards ! "
Bingo... problem solved .
 
[1] If you pump the pedal, pedal comes up, & you THEN have a hard brake, it is NOT air in the system. It is a mechanical problem. Most likely the prod in the booster travels too far before it contacts the piston in the m/cl. Some prods are adjustable/
[2] Squishing noise is air entering the booster chamber & is a normal operation. Some are noisier than others....
 
boosted said:
The master cylinder was new but old. I did not bench bleed it but have bled the system 4 times now. No air to be seen. Could it be a bad master cylinder? I hate to spend the 200 bucks for a new wilwood one if I don't have to.
Click to expand...
I've had a brand new MC do this, Mfr sent a replacement, didn't want the first one back. Gave it to a friend and he pulled it apart and found the bore was good but one seal was torn. Got rebuild kit with new seals, problem solved.
 
To me it sounds like your system has a mechanical springiness in it that should not be there.
Check that all the pads are flat and sitting squarely on the discs with full contact, and that no caliper brackets or pins are bent, and that no pistons are overly extended out of the bores.
You will probably need a helper on the pedal while you observe the action.I would start at the back.

What I have seen (among other things) is a bent steel-backer on a pad. The hydraulic pressure was adequate to flatten it with several pumps. But upon releasing the pedal, the bent pad would relax and push the piston up into the bore. and then it would take a few pumps to flatten it out again. Same with bent other stuff, and or a pile of silicon-type anti-squeal material globbed onto the back of the bad, or even a folded-over stainless shim, that only contacted half the piston, as well as bent brackets, that tipped the piston to one side..
If while testing, any one caliper or padset seems to show more movement than a few thousands of an inch, then that is the one I would go after first.

If you just can't find it;
Remove all the calipers and C-clamp the pistons to the bottom of the bores. This will allow NO mechanical movement. Now, if the pedal still goes soft after pumping it up and releasing; then you for sure have a hydraulic problem, and most likely, it will be in the M/C.
Good luck man; I know how frustrating this can be.
 
Thank you to everyone. A quick update..No fluid on the floor from the rear seal of the m/c. I did have to put an adjustable rod in to compensate for the thickness of the offset bracket. I made sure it was seated and adjusted. Wide and I will bleed the m/c tomorrow and then start the brakes again...
 
Another way to troubleshoot this ---assuming it's something like AJ mentioned-- is to buy a couple/ 3 inverted flare plugs and unions. This will allow you to pull loose sections of the lines, bleed it down to where you plugged it and see if the pedal gets hard. If it does, and what was plugged "does not" you have a problem in that section.

With manual 4W discs, the pedal should be ROCK HARD
 
I've had this problem since day one. I'm curious to see what you find. I've never replaced my master.
 
Do you need an adjustable push rod when you upgrade to a modern master with the 4 to 2 bolt hole adapter, due to the thickness of the adapter plate?
 
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