Changed front pads now no brakes on front - Team Camaro Tech
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post #1 of 23 (permalink) Old Oct 11th, 17, 08:22 PM Thread Starter
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Wayne
 
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Changed front pads now no brakes on front

I've searched the posts and didn't find exactly what's going on. It's a 69 SS with factory disc and drum brakes. I know the mc and brakes were replaced before I got the car about 8 years ago. The front right brake was always tighter than the left and I finally took a good look at the calipers and pads to find out what was going on. After looking at both sides I found that the 2 short sleeves that the long bolts go through were rusted in place. I cleaned, replaced and lubed parts as needed on both sides and installed new pads. Also I didn't touch the rear brakes. After I put it together I was ready to test drive and started the engine and found that the pedal goes to the floor now. Pumping it doesn't help much.

Now, while I was trying to figure out what was originally causing the tight pads problem, I took the pads off and pumped the brakes to see if the caliper piston would move out after I had taken the C clamp off. I pushed the pedal pretty hard while trying that for both sides. Tonight I bled the front brakes just for grins to see if that would help. There was air in the lines on both sides. The air quit coming out on the right and the air never did seem to completely stop on the left. So I still have the same results. With the engine running or off when pressure is applied to the pedal it will go to the floor. After reading what I have just written I'm thinking I have blown out the rubber piston cup in the mc. Is that a good possibility? I don't want to pull things apart before I have a reasonably good idea of what's going on. What do you think?

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post #2 of 23 (permalink) Old Oct 12th, 17, 05:21 AM
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Try bleeding the mc. Then bleed all corners starting with rear pass/rear driver/ front pass/front driver
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post #3 of 23 (permalink) Old Oct 12th, 17, 06:07 AM
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Chris
 
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Re: Changed front pads now no brakes on front

Steven has a good point in trying to rebleed everything. If you pushed hard on the brake pedal with the pads out you would have hyper-extended the piston past a point of travel it has ever seen in the past with the pads in. Is it possible you dislodged the seal from its groove and the piston isn't returning completely within its bore.

Take a look at the link below about the metering valve, or "hold-off" valve on the '69's. You may need to press the button on the back of that valve to bleed the front brakes. The button is very hard to press so you may need to pry it back with something and wedge something in to keep it depressed. Also, since your brake pedal went to the floor, the piston in the MC has traveled way past its normal travel range and this can cause the seals to be damaged if a slight ridge had been built up in the bore and the piston seals move past this ridge they can be damaged and start leaking so be on the lookout for this. Its best to find the max travel of the brake pedal before you start the brake job and put a block of wood or something under the brake pedal so when you depress the pedal to bleed the brakes after your change things the pedal does not go past its normal operating range.

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post #4 of 23 (permalink) Old Oct 12th, 17, 06:13 PM Thread Starter
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Re: Changed front pads now no brakes on front

Tonight I tried something I thought of that may or may not apply to whether the master cylinder is good. First, I pumped the brakes and the pedal will go to the floor. Next, I disconnected the front line from the front side of the mc and screwed a plug into it. When I put pressure on the brake pedal, it holds. I took the plug out and reconnected the line and it goes to the floor again. My conclusion is that the mc is good. Does that sound right? If that is right should I pull the front wheels off and check for something going on with the pads or pistons?

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post #5 of 23 (permalink) Old Oct 12th, 17, 07:29 PM
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Re: Changed front pads now no brakes on front

Google bleeding GM brakes and see that there's a valve in the block that disables the end that loses pressure if you don't follow the procedure.
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post #6 of 23 (permalink) Old Oct 12th, 17, 07:53 PM
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Re: Changed front pads now no brakes on front

I guess I'd first verify that there are no issues with the flexible hoses to your calipers. If the hoses are cracked on the outside, then obviously they should be replaced. It is possible for the hoses to deterioriate on the inside where you cannot see it, but look perfectly fine on the outside. Interior deterioration can actually cause that hose to act as a check valve inhibiting the ability to properly bleed the brakes. Same holds true for the rear hose from the diff to the hard line on the body. I don't know that this is a contributor to your problem, but wanted to mention it. New hoses are cheap insurance.

I still think you need to bench bleed the MC again to make sure all the air is out. It doesn't take much air to give you a poor pedal. Your test suggests that you are not getting any leakage around the piston in the MC, but like I said in my earlier post, watch for leakage up where the push rod enters the MC under the dash. When you bench bleed the MC give it some time between each stroke and keep it up until you get zero bubbles.

I use a Motive power bleeder that works on a pump up tank like a garden sprayer. Since I started using one of those years ago, even if I have a bunch of air in the line it blows out quickly and fluid follows soon thereafter, but I do remember the periodic frustration of manual bleeding using the old foot on the pedal method. My wife did not like that method one bit.

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post #7 of 23 (permalink) Old Oct 12th, 17, 08:00 PM
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Re: Changed front pads now no brakes on front

This posting may be of interest to you:

https://www.camaros.net/forums/16-bra...-bleeding.html

'69 Z/28, Lemans Blue/White Stripes, DZ302, Tremec Magnum, 4.10, Procar Elite Seats,
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post #8 of 23 (permalink) Old Oct 12th, 17, 08:13 PM Thread Starter
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Wayne
 
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Re: Changed front pads now no brakes on front

I keep ruling out air in the lines due to the fact that the brakes were working okay before I replaced the pads and cleaned the calipers. I didn't think I got air in the lines when I did the work. But it is worth a try since I can't explain the problem. I can probably do that tomorrow. Also, just for information, I tried using a big screw driver and a thin piece of wood against the brake booster to see if I could push the button on the back of the metering valve and it wouldn't budge. I had removed a rubber cap that was on it and it looked like it had been filled with grease but looked kind of dirty in it also.

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post #9 of 23 (permalink) Old Oct 12th, 17, 10:22 PM
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Re: Changed front pads now no brakes on front

If I'm reading the original brake issue correctly... it sounded like your brakes worked fine before replacing the front pads, just that one of the front tires/brake rotors was tighter to turn when no brakes were applied (due to rusted caliper sleeves).
When you replaced the front pads, you did not disconnect any of the brake lines.... you just moved the calipers around to clean and lube them.
You also made no mention of any leaking brake fluid while attempting to apply the brakes before... or after you replaced the front pads.

As Wayne previously mentioned, you may want to take a closer look at both of the flexible rubber hoses that attach to your calipers. Since you disconnect the front brake line from the MC, your going to have to bleed the front brakes to confirm there is no air in the lines before trouble shooting as described below.

Have someone else push the brake pedal while you carefully watch each of the front rubber brake hoses. Look to see if any portion of either rubber brake hose is "ballooning" as pressure is applied to the brake pedal. Chances are that as you were moving the calipers around during your R&R of the front brake pads, something way have been damaged in one (or both) of your front rubber brake hoses. A ballooning rubber brake hose would cause the new issues you are describing.

Whenever I have to remove the front brake calipers, I always support the each calipers with a wire hanger attached between the calipers and something inside the wheel well to keep the calipers from just hanging and putting stress on the rubber brake hoses.
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post #10 of 23 (permalink) Old Oct 13th, 17, 08:42 AM
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Re: Changed front pads now no brakes on front

What kind of distribution block are you using? Does it have a differential pressure switch and is it connected to the brake light? Does the brake light stay on all the time, even when the parking brake is not engaged? I think what happened is that when you pumped on the brakes with out having the caliper with pads over the rotor the spool in the distribution block is not centered anymore.
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post #11 of 23 (permalink) Old Oct 13th, 17, 09:35 AM
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Al
 
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Re: Changed front pads now no brakes on front

I doubt the master cylinder is bad due to your test.
Loosen the output line on the metering valve. Apply
pressure to the pedal. If you don't get any fluid from
the loose line fitting then the metering valve is
bad/stuck. If you do get fluid, tighten that fitting and
keep working your way forward using the same method
at each fitting until you find the fault. My guess is the
problem is at the calipers due to pressing the pedal with
the pads/rotors removed. Never do that. Now you'll get
to rebuild or replace the calipers. I would do that from
a safety standpoint now.
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post #12 of 23 (permalink) Old Oct 13th, 17, 06:55 PM
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Chris
 
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Re: Changed front pads now no brakes on front

Quote:
Originally Posted by 69ndpce View Post
I keep ruling out air in the lines due to the fact that the brakes were working okay before I replaced the pads and cleaned the calipers. I didn't think I got air in the lines when I did the work. But it is worth a try since I can't explain the problem. I can probably do that tomorrow. Also, just for information, I tried using a big screw driver and a thin piece of wood against the brake booster to see if I could push the button on the back of the metering valve and it wouldn't budge. I had removed a rubber cap that was on it and it looked like it had been filled with grease but looked kind of dirty in it also.
The button on the back of the metering valve moves very little, way less than than one would think. I removed and rebuilt mine last year and did the same thing when bleeding my brakes - jammed a wood wedge between the button and the booster, seemed to work fine for the purposes of bleeding. Seemed to keep it open enough to permit the front brakes to bleed (with my Motive Power Bleeder).

Check the spool location in the distribution block too.

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post #13 of 23 (permalink) Old Oct 13th, 17, 08:15 PM Thread Starter
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Wayne
 
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Re: Changed front pads now no brakes on front

Okay, this is where I am now. First I jacked the front end up and turned the wheels by hand. There is drag on both. They don't free spin at all. I removed the left wheel and looked at the caliper and the pads are touching and I can see the piston and seal and all looks dry. Second, I've read how to bench bleed and then gravity bleed so I thought I'd try that next. I have the rear higher by about a foot. I've stopped at the master cylinder and here's why. I had 2 clear hoses going from the bleeders into the bottom of both bowls. I kept the bleeders tight until I had a helper push the pedal and release. I loosened them at the same time and closed them at the same time. The rear cleared of bubbles after a few pushes. The front never did clear of bubbles. I tightened the rear bleeder and just worked with the front and it would push about the same amount of bubbles every time, which were a lot. I could see 2 holes at the bottom of the front bowl and it would blow some bubbles out of the front hole too. There are no wet spots any where nor did the fluid level ever drop. It appears that it is sucking air in somewhere but not leaking. At this point I'm guessing I damaged the caliper piston assemblies when I pushed the brakes without the pads in. Also, I noticed, the other day, that air would never stop coming out especially of the left caliper bleeder when I tried to bleed the front brakes. More information is that the front and rear hoses are about 3 years old now and check out good. Fluid comes out okay to the front and rear so the flow isn't the problem. What do you think now? The calipers? And if so, can a shade tree mechanic like me rebuild them? Thanks to everyone for their help too.

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post #14 of 23 (permalink) Old Oct 14th, 17, 04:50 AM
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Re: Changed front pads now no brakes on front

Did you open the top of the MC before you pushed the caliper pistons back in? If you didn't, then I would not eliminate the MC or a brake fluid leak somewhere in the system.

If you did remove the top of the MC and pushed the caliper pistons back in slowly, then focus on the calipers themselves. It is probably time for a rebuild. Yes, they are rebuildable and yes, you can do it yourself. Rebuild kits are inexpensive. Once the caliper is apart, you will be able to tell if the inside of the caliper walls need cleaning. Sometimes they score, sometimes they rust at the edges. If either are light enough, just clean 'em up and re-assemble using brake fluid. Before reinstalling, evaluate the front brake hoses. Replace as needed. Then bleed the system again: right rear, left rear, right front, left front.
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post #15 of 23 (permalink) Old Oct 14th, 17, 04:52 AM
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Re: Changed front pads now no brakes on front

They also sell MC rebuild kits. It's an easy job to do on your workbench.
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