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Author Topic: Good God In Heaven ... Please Help Me With These Brakes!!  (Read 8295 times)
no69x-44
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« on: August 28, 2008, 08:45:46 PM »

I don't know what else to do or where else to turn anymore.  I have a '69 and after 5+ years of restoring this blasted beast, it wants to fight me to the bitter end!  I have replaced EVERYTHING in the brake system.  Some parts several times.  This is the deal:

All new brake lines - complete front to back.
All new brake hoses
New Front Calipers
New Power Booster
Re-built Original Master Cylinder
Original Proportioning Valve
Original Distribution Block
Long Rod in the Power Booster to the Master

I think that covers everything.  This is an original Big Block Car and original front disc brake car.  The problem I'm having is with the front disc brakes.  What was happening is that I had to pump the brake pedal 6 times before the front brakes would actually grab enough to stop the wheel.  Each pump of the pedal added a bit more restance ... the about 6 pumps of the pedal is what it took before you could not spin the wheel.

I switched out the repro master cylinder and repro proportioning valve and installed a original master cylinder (re-built) and the original proportioning valve.  Now it is 3 pumps of the brake pedal to completely stop the front wheel.  Better, but still not quite right.  I have bleed the master cylinder and the front brakes a million times and the fluid comes out in a nice steady stream ... No air at all.
The back Drums have never been an issue and work fine.

So I'm done here.  I have nothing left to try.  I'm out of bullets.  If anybody out there that is a brake expert and has any advise at all ... I'm all ears.
Thanks in advance for any and all help.
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KevinW
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« Reply #1 on: August 28, 2008, 09:24:48 PM »

Rob, you are testing the brakes with the engine running, correct?  I dont think I am doing anything on Monday and can come over to look it over if you want. Kev
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no69x-44
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« Reply #2 on: August 28, 2008, 09:34:40 PM »

Kevin - You know ... As I was writting this - I was thinking to myself that I have never tested the brakes with the car running. I was wondering if the power booster/vaccum would make any differance here.  I'm going to give that shot in the morning.  Do ya' really think that could be it?   Stay tuned ...
« Last Edit: August 28, 2008, 09:43:55 PM by no69x-44 » Logged
hotrod68
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« Reply #3 on: August 28, 2008, 11:29:27 PM »

I've gotten bad rebuilt master cylinders--that's possible. But if you have ANY air in the system, front or back, it can cause problems. If it were me, I'd bleed the whole brake system once again to make double sure there is no air in it. Just a thought and good luck!
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HotRod'68  1968 coupe undergoing frame-off resto/rod. 386/350/4.11s
melav8r
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« Reply #4 on: August 29, 2008, 12:29:15 AM »

The 69 Chev Chasis Service Manual says: "The spring loaded end of the pressure metering valve must be depressed while bleeding. This can be done by depressing and holding in the plunger in the end of the valve either by hand or by clamping."
They are referring to the proportioning valve mounted under the master for the front brakes.
Since you swapped out the master cylinder you should re-bleed the entire system if you haven't already done so. Also does the rear port in your master cylinder have a check valve installed? This keeps residual pressure to the rear brakes and can cause a spongy brake pedal.
I personally have had good results using a Mityvac Brake Bleeder without having to touch the proportioning valve. Uses a handheld vacuum pump to bleed the brakes. Available at Napa, Harbor Freight, etc...
good luck.
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KevinW
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« Reply #5 on: August 29, 2008, 05:37:38 AM »

Rob, power brakes need the vacuum to work properly.  I can also bring my homemade power bleeder with me to see if that helps.  I can think of a couple things to try to test, but take 2 people.
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jdv69z
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« Reply #6 on: August 29, 2008, 10:52:48 AM »

I had had good results using gravity to bleed my brakes. Just keep bleeder fitting at the wheel attached to hose submerged in brake fluid to prevent air from backing in to the system, and leave master cylinder cover off, Also make sure master cylinder does not empty out, or you'll have to start over.

Jimmy V.
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Jimmy V.
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« Reply #7 on: August 29, 2008, 03:26:29 PM »

I had the same trouble on a 68 car and it ended up to be a bad proportioning valve [large round one with large nut on front] The valve was not allowing enough fluid forward to operate front discs. Take off the line at the proportioning valve and pump the pedal lightly to see if any brake fluid is passing through the line.
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1968 Z28 LA Built
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no69x-44
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« Reply #8 on: August 29, 2008, 10:45:17 PM »

Guys - Thanks for the replies.  Keep them coming if some thing should come you.  I sent a good part of the day messin' with the front brakes and still nothing.

Kevin - I did start the car and tried the brakes, but the pedal goes down to the floor.  I tried creeping the car a little and the back brakes did grab, but felt like nothing in the front.  The paint guy has time this week to do touch up work and final buff on the car for me.  The car is there now and hopefully I will get the car back home in couple of weeks - I'm hoping maybe after next week.   I'll give you a call when I get the car back (if it doesn't end up in paint/touch up prison) and maybe you can stop over one weekend day and get this Voodoo spell off!

I'm so close to driving this car again, I can taste it.  Well, I guess I can actually drive it ...  But I just won't be able to really stop it!
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KevinW
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« Reply #9 on: August 30, 2008, 07:46:44 AM »

Rob, OK.  What I was going to try was take the MC cover off and watch the piston movement through the vent hole as you push down on the brake.  We should see the MC piston start moving right away.  If it does not, then something wrong with the linkage.  If that is good, we take the tires off and check the distance of the pads and watch/feel them as the pedal is pressed.
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william
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« Reply #10 on: August 30, 2008, 09:59:16 AM »

I'm not trying to be insulting but there is a right and left caliper for 69. If they are reversed the bleeders will not be at the highest point and there will always be air in the system. I have seen several experienced people do this.

Also if you used stainless lines there may be a mismatch in the flares. We had a fitting at the distribution block that would draw air but not leak fluid.
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JohnZ
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« Reply #11 on: August 30, 2008, 10:24:02 AM »

Did you bench-bleed the master cylinder before installing it? If not, any remaining air in the bore is almost impossible to get out without pressure-bleeding.
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Sauron327
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« Reply #12 on: August 30, 2008, 10:42:26 AM »

John,
 Wasn't onebad34 having similar problems. I couldn't find past post. And doesn't the piston in the MC have to return it's stroke fully to operate properly? Or would that affect the rears as well?
 I also had to give my friend my spare MC to replace his "new" one which also would not bleed. Fronts then bled straight away. Bench bled first as you say.
 I have been lucky but my days are numbered. Many are having replacement part problems. 
 
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KevinW
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« Reply #13 on: August 30, 2008, 04:07:50 PM »

If I go over to Robs, I will bring my pressure bleeding adapter.  I want to make sure his MC/rod and booster linkage is working properly first.  I will check his calipers too.  Thanks William!
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no69x-44
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« Reply #14 on: August 30, 2008, 04:39:22 PM »

Hey guys thanks for the help and please don't be shy with any additional ideas.  The Calipers are on correctly.  The Bleeders are on the bottom.  If the left one was on the right side adn visa versa - then the bleeder screws would on the top of the calipers and that would be an air issue.
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Gramps69Z
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« Reply #15 on: August 30, 2008, 07:14:54 PM »

Hey guys thanks for the help and please don't be shy with any additional ideas.  The Calipers are on correctly.  The Bleeders are on the bottom.  If the left one was on the right side adn visa versa - then the bleeder screws would on the top of the calipers and that would be an air issue.


The bleeders should be on the top.   If not you will have an air issue.
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Captain John Wykoff
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I'm sick and tired of mismanagement and disappointment. 
I'm a COWBOYS fan.
melav8r
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« Reply #16 on: August 30, 2008, 07:26:02 PM »

That is correct, bleeder screws need to be on top!!
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no69x-44
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« Reply #17 on: August 30, 2008, 08:53:35 PM »

Guys ... Yeah I know ... My bad on the bleeders.  What I meant to say is the top.  I'll double check that, but I'm sure they are installed correctly. I have banging my head on this problem for so long now, that I'm getting dizzy.
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JohnZ
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« Reply #18 on: August 31, 2008, 10:53:31 AM »

If I go over to Robs, I will bring my pressure bleeding adapter.  I want to make sure his MC/rod and booster linkage is working properly first.  I will check his calipers too.  Thanks William!

Make sure his booster-to-pedal rod clevis is adjusted so it provides the necessary free play, and the booster-to-master cylinder rod is correct so it doesn't move the primary piston forward at rest, covering up the compensating port hole.
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Steve68
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« Reply #19 on: August 31, 2008, 06:17:04 PM »

With the parking brake not engaged, ignition switch in the "on" position, is the dash brake light "on" or "off"?
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no69x-44
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« Reply #20 on: August 31, 2008, 08:02:06 PM »

With the parking brake not engaged, ignition switch in the "on" position, is the dash brake light "on" or "off"?

Hmmm ... Funny you should ask.  The Brake light is "on".
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KevinW
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« Reply #21 on: August 31, 2008, 08:07:09 PM »

Hmm, that could mean the dist block has shifted internally.
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no69x-44
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« Reply #22 on: August 31, 2008, 09:10:50 PM »

Hmm, that could mean the dist block has shifted internally.

But the brake light goes off when the car is started ...   Doesn't the distribution block pretty much just pass fluid?  I didn't think there were really any moving parts in there.
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Sauron327
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« Reply #23 on: August 31, 2008, 09:42:46 PM »

There aren't. I see from your list you using the origional proportioning valve (the round one)

Pete ( member name: one bad 34) had a problem and I told him to temporarily eliminate the PV with just a brake line to eliminate PV as a problem. If the calipers operate correctly then the problem has been isolated. Now get another PV or rebuild yours.
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KevinW
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« Reply #24 on: September 01, 2008, 06:44:00 AM »

Hmm, that could mean the dist block has shifted internally.

But the brake light goes off when the car is started ...   Doesn't the distribution block pretty much just pass fluid?  I didn't think there were really any moving parts in there.

Rob, if the light goes out when started then its OK, thought you meant it was on all the time.  Actually there is 1 moving part inside.  Its a coke bottle shaped piston that is between the rear and the front brake lines.  If you hit the brake and you lose a line, the pressure difference moves the piston and grounds the light indicating brake failure. That is why there is that electrical connection thing on the side of the block Smiley  You saw your car this weekend  and verified the calipers, correct?
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Wallace
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« Reply #25 on: September 01, 2008, 06:48:36 AM »

I think your problem is the caliper installation.  The bleeder screws need to be on top, otherwise the air will be trapped.  I have and original 69 BB and the bleeders have always been on top.  Check out this web site.  http://www.wikihow.com/Install-Brake-Calipers-on-Car-Wheels
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Sauron327
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« Reply #26 on: September 01, 2008, 07:41:16 AM »

I should have been more explcit with my explanation.
                   
Dist block by John Z.:
  "The distribution block has no valving in it at all - it only activates its internal differential pressure warning switch (which lights the warning lamp in the cluster) when it senses a pressure differential between the front and rear systems."
   
     It senses a change but does not possess pressure management capabilities. Scott 
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no69x-44
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« Reply #27 on: September 02, 2008, 11:21:26 AM »

OK - Quick update. I was getting brain freeze and second guessing myself, but now after thinking about this I know the calipers are on correctly.  There really is only only one way for them to go one without force fitting something.  For the recored, the bleeders are on the top of the calipers and point torwards the rear of the car on both sides.
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no69x-44
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« Reply #28 on: September 03, 2008, 02:27:35 PM »

Oh the sun is out, the sky is blue, the birds are singing and it's such a beautiful day!  "Are my brakes working", you ask?  Why yes ... Yes the are!  Thanks for asking.  My car now stops like a car should and I have front disc brakes engaging as designed.  Life is good again!

For those intrested in the fix here ...  I had a pair of re-pro calipers on the front as a temp thing as I wanted to send my original Delco calipers put to be re-built.  In total frustration ... This morning I swapped out the new calipers and put my old originals (new pads) on the car ... Bleed the front brakes and BAMM ... I now have working front disc brakes that stop on a dime! 

Kevin - I just may be ready for that cruise over to your house!! Smiley

Thanks all for the help. It's always much appreciated.
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KevinW
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« Reply #29 on: September 03, 2008, 07:11:09 PM »

Rob, congrats!  I will be home on sunday closing the pool, stop on over!
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