Brakes have me baffled!

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MB43

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I can't figure out what's up with my brakes.

Here's the background. The brakes in the car have always sucked. Until recently I had a stock cast iron master cylinder and drums all around. I upgraded the front to Wilwood discs, replaced the master cylinder with an aluminum unit I bought from GregZ @ MagnumHP a while ago, replaced both real wheel cylinders, replaced the line lock with a brane new unit and replaced all of the lines between the master, line lock and distribution block.

I've adjusted the rear brakes, bled them over and over, bled the fronts, and bled the master before I installed it. I replaced the line lock today, and when I did I re-bled the fronts. Nothing but pure fluid coming out, no air.

When I step on the pedal, it has about 3 inches of travel before I get anything. When I do get something, I hear and feel a "clunk" like I've hit something solid. And it doesn't stop at all while it's within that 3 inches. Once I get past that point, I have only about 1 inch of travel before I can't move it anymore, but it's not to the floor. In that 1 inch, I've got a little brakes or more brakes, but not enough to lock up the wheels. If I go in reverse about 30 MPH and jam on the pedal it'll lock up the wheels, but I don't think it'll do it going forward.

If I pump it up 4 or 5 times it'll get a little firmer - but not much. It'll give me about 1/2 more travel before I hit that solid stop. After I let off of it (after pumping) I hear the sound of fluid moving around, but I can't tell where it's coming from, but it's somewhere in the area of the master cylinder, the lines to/from it or the line lock.

Any ideas? Suggestions?
 
How are the brake lines ? Do you have a swelling line ?

Maybe a bad adjuster in the rear brakes. Try replacing the hardware. Its cheap.
 
Have you tried reverse bleeding them? I think that is what it is called. You pump the fluid from the wheel backwards up to the master cylinder.

Jack
 
AdamR said:
How are the brake lines ? Do you have a swelling line ?

Maybe a bad adjuster in the rear brakes. Try replacing the hardware. Its cheap.
Click to expand...

I've got new braided hoses in the front (from Wilwood), and I think everything else is solid line...? Is there any other rubber aside from what used to be on the front brakes?

The adjusters are working, I checked that. The rear brakes are tight.
 
Coyote Jack said:
Have you tried reverse bleeding them? I think that is what it is called. You pump the fluid from the wheel backwards up to the master cylinder.

Jack
Click to expand...

No, I didn't try that. But after I installed the new rear wheel cylinders I gravity bled them - left the bleeder screws open for a while. Then I did the normal pump, pump, pump, hold it, open the bleeder, close it, get off the pedal thing. It would've been much easier had I had somebody else to help me. :lol:
 
Also, did the new calipers come pre-loaded. If not, then from what I have been told the reverse bleeding is the only way to get all the air out.

Jack
 
Mikel, theres a rubber line going from the main front to rear line to the rear housing. Your steel lines could also be rusting. If they get thing they will pulse every time you step on the brakes til it pops.

To make bleeding brakes by your self easier, Take an big old jar ( I have a old glass helmans jar) a long piece of vacume line that you can push over the bleeder. Pop a hole in the cap of the jar for the other end of the hose and stick it in till its almost at the bottm. Fill the jar 1/2 way with clean fluid.

Now you can open the bleeder Hook the line up to it and start pumping. Because the other end of the line is submerge in fluid it wont pick up any air. Just keep an eye on the fluid level in the master. It will empty fast. And remember start at the furthest bleeder from the master and work to the closest.
 
Coyote Jack said:
Also, did the new calipers come pre-loaded. If not, then from what I have been told the reverse bleeding is the only way to get all the air out.

Jack
Click to expand...

Pre-loaded? With what?

When I open up the front bleeders (4 per side, I only bleed the top 2) all I get is fluid, no air.
 
AdamR said:
Mikel, theres a rubber line going from the main front to rear line to the rear housing. Your steel lines could also be rusting. If they get thing they will pulse every time you step on the brakes til it pops.
Click to expand...

Oh yeah, I forgot about that line. I'll have a look at it tomorrow and see what kind of condition it's in. The steel lines are getting old, but are in ok shape. I had no problems getting them off the old wheel cylinders, and they looked to be in half-way decent shape.

To make bleeding brakes by your self easier, Take an big old jar ( I have a old glass helmans jar) a long piece of vacume line that you can push over the bleeder. Pop a hole in the cap of the jar for the other end of the hose and stick it in till its almost at the bottm. Fill the jar 1/2 way with clean fluid.

Now you can open the bleeder Hook the line up to it and start pumping. Because the other end of the line is submerge in fluid it wont pick up any air. Just keep an eye on the fluid level in the master. It will empty fast. And remember start at the furthest bleeder from the master and work to the closest.
Click to expand...

Every time I try to do a "do it by myself" bleeder deal, I wind up with more air in the system. I've got a wife who helps without much complaining, and my neighbors are more than happen to help out.
 
Hey, what push rod are you using with tha master ? If you have the adapter yo've moved the master out about a 1/2" and are probably trying to pull the push rod out of the back of the master. Theres your clunk and fluid noise. You may need to get the adjustable push rod.
 
AdamR said:
Hey, what push rod are you using with tha master ? If you have the adapter yo've moved the master out about a 1/2" and are probably trying to pull the push rod out of the back of the master. Theres your clunk and fluid noise. You may need to get the adjustable push rod.
Click to expand...

I get the clunk on the down stroke... I was thinking that if it was too short, when I first step on the pedal it's got a longer way to travel before it hits the piston in the master. Does that sound right?
 
I think the further you push the pedal down the further it pulls the push rod. But maybe thats backwards?
 
AdamR said:
I think the further you push the pedal down the further it pulls the push rod. But maybe thats backwards?
Click to expand...

That's backwards... It pushes the pushrod, not pulls.
 
Something else I was wondering about Mikel. Is the travel distance of the pushrod different in the new master from the old one. If it is a longer throw then the connection point on the pedal arm would have to be changed to a lower position wouldn't it? Just thinking out loud.

Pre-loaded means they come filled with brake fluid.

Jack
 
Do you have residual pressure in the system?
Fronts should be about 3# and rears 8-10#s

With no peddle pressure crack the bleeders you should get a slight surge from the bleeder.
 
Coyote Jack said:
Something else I was wondering about Mikel. Is the travel distance of the pushrod different in the new master from the old one.
Click to expand...

Yeah, I'm sure it is - I have an adapter plate on the firewall to go from the 4 bolt to the 2 bolt master.

If it is a longer throw then the connection point on the pedal arm would have to be changed to a lower position wouldn't it? Just thinking out loud.
Click to expand...

Is the pedal adjustable?

I'm thinking I might just pick up one of those adjustable brake pushrods.

Pre-loaded means they come filled with brake fluid.
Click to expand...

Oh. No, it wasn't pre-loaded. I've never seen a master cylinder come pre-loaded!
 
cuda66273 said:
Do you have residual pressure in the system?
Fronts should be about 3# and rears 8-10#s

With no peddle pressure crack the bleeders you should get a slight surge from the bleeder.
Click to expand...

No, I don't have an external residual pressure valve. But the master should have one built-in, at least on the fronts, no?

I have a 10# pressure valve that I used on the fronts when I had drum brakes, but it's not installed.
 
AdamR said:
Hey, what push rod are you using with tha master ? If you have the adapter yo've moved the master out about a 1/2" and are probably trying to pull the push rod out of the back of the master. Theres your clunk and fluid noise. You may need to get the adjustable push rod.
Click to expand...

Why is there such a big difference in the price of this part? (Mopar P5249316)

Jegs has it for $62.99.
Summit has it for $65.95, but no stock.
Mancini has it for $70.95, but they also have their own version for $39.95.
Moparts Racing has it for $55.00.
 
Coyote Jack said:
When I was talking about pre-loaded it was the calipers, not the master cylinder.

Jack
Click to expand...

Oh, ok.

Still no. ;-)
 
If it was up to me, I would reverse bleed them first. It is the cheapest thing to try if you can borrow the kit from somebody.

Jack
 
Ok, gentlemen... The verdict is in.

The master cylinder was no good.

I was going to replace the pushrod with the adjustable kit I picked up, and was going to pull out the stock distribution block and put in a 'T' in it's place. And then install the Wilwood proportioning valve on the back line.

Before I did any of that, I bled all four corners again. The same result, a mushy pedal.

So I stopped in at AutoZone and picked up a new (not re-man) master for an '81 D150, bench bled it for 40 minutes - made sure not a single bubble was to be found anywhere - installed it and bled everything again.

I've got brakes! And a good pedal!

I'm still going to remove the stock valve and put in the Wilwood proportioning valve, but for the time being it stops just fine. Even the line lock works, I can hold the car up to around 3500 before it pulls through the brakes. I can lock up all four wheels without pumping the pedal.
 
Glad to see this worked good for you. It stinks spending all that money on brakes and having a mushy pedal.
 
moparracer said:
Glad to see this worked good for you. It stinks spending all that money on brakes and having a mushy pedal.
Click to expand...

You're telling me! ](*,)

Now, alll I need is for it to be nice on Sunday so I can finally get out to the track. :toothy2:
 
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