[Jimbro727]

Originally Posted by HWYSTR455

Yeah, I honestly can't remember the orientation of the lines/ports on the 2nd gen F-bodies, I ditched mine years ago for an adjustable. If you looked at the factory service manual, and it's clear which goes where, then obviously you're good with that.

On the rear adjustment, crank those things out there until you feel resistence in the adjuster, like with it applying brakes. This is just for troubleshooting to see if the pedal changes. If it does make a diff, you know where the problem may lay.

Pushrod measurement, well, may sound cheesy, but I used a paperclip bent from the flange to the cup, then measured the paperclip. Worked for me. If there's an issue with the pedal as you're talking about, it's going to be obvious. I kinda don't think that's it, because you say there's no 'loose' or 'free' travel of the pedal. You can take the MC cover off, and as you depress the pedal, you should see fluid movement, can try that as a general indicator.

Power/pressure bleed is the best, period. If you've got a rig for it, that's the way to go. Same thing, start at the furthest wheel, and make sure the tank is full.

Warning switch, that will tell you if the prop is boogered, in most cases. If it's a bias rod problem, the light will come on.

On the pedal, in the car, the upper hole is for manual brakes, the lower for power, or that's how I remember it. Wouldn't hurt to try a different one I guess. For a manual setup, using the power hole will make the pedal hard.

Hm, a bad booster causing a low pedal, not sure on that one. I know when there's no/low assist, due to a bad booster, the pedal is hard. Someone once told me that when you have your foot lightly on the pedal, and you start the car, the pedal should slowly go down, which indicates a good booster, but don't know how true that is. Do you have the original factory booster still? Might be able to try it. If you bought the booster from DSE, they should be troubleshooting it with you. Call them.

Thanks, I'm going to play with the rear shoe adjustment in a few minutes.

I like your pushrod measurement method lol, I'm going to give that a shot, too.

Yeah, after bleeding for hours and hours, the $60 bucks or whatever it cost for the pressure bleeder just seemed worth it.

I'm using the lower pedal hole - so I don't think that's the issue, unless there's something else out of alignment down there.

I wasn't sure about the booster either. I didn't get it from DSE, it's from AutoZone, I don't recall the brand. I could figure it out and give them a ring though, that'd at least rule that out.

The warning switch sounds like it'd be a big help - but I don't know how to get the connector to fit. I'm pretty sure I broke the connector trying to get it on, because I had it on the pin that comes out of the combo valve, and then I tried to pull the connector back off, and it left a small metal collar on the pin, which I'm pretty sure broke off from inside, so I need to find a new connector. I don't see how the connector could fit, though, it seems like the pin is too high. Is that how it's supposed to be?

I think that I just had a breakthrough though - I had previously thought that my brake pressure gauge didn't come with the right fitting for my calipers, but I found the correct one. I was able to measure the pressure going to the front left caliper, and the highest I measured was 600PSI. I'm supposed to get more like 1200-1500, right? What would cause that low pressure?

Thanks again

[HWYSTR455]

Yeah, 600 is way too low, and that's MC and/or booster issues. Or a leak! Well, could be that the rear shoes are traveling too far before hitting the drum too, not enough sweep on the pedal/MC.

Yup, you need a new connector, Help products has them, and since you have to splice anyway, you can add a length. The aftermarket prop valves, some do have a different connector, and may stand off higher, making the original connector not fit well. Honestly, I just said effit, and left mine off.

Hm on the booster, might be the issue. There's some referb shops that do those specifically, the 2nd gens, might want to look into that, could be your problem all together. There was something wierd about the 79-81 boosters, can't recall, but if they list them for 70 1/2 - 81, might be your clue. Check PY, think they're affordable, and they're correct.

MPBrake.com has the push rod depth checker, found that earlier doing a search, never knew they had one! 20 bucks is worth it!

.

[motorcitymusclecar]

I hate to jump in so late in the game but i hae seen this 1000 times - it is in the bleeding of the brakes. It takes several times to bleed a freash system. It could take as many as 6 times with a day inbetween for bubbles to settle. The more you bleed the better it will get. All the movement of fluid creates bubbles and the waiting game lets them all collect. We all over think things at times - take a break and go back in a couple of days. hope this helps john

[BVR421]

Originally Posted by low63gp

Well, I have been having the opposite problem, too soon of a pedal that will put your face in the dash but I do know that on my 63 GP,

All 60s cars with power BIG brakes like yours come on fast and hard.
Its for you to learn to apply gently and modulate the pressure.
Some of that can be improved with proper adjustment of the leading edge. Check your manual for detailed procedure, and it is a detailed adjustment.
Those big 11" brakes will stop you from any speed if correctly set up but usually only once from high speed and then they need a cool down,
Mine took some getting used to when I first got my 63, drove it 3 years as a daily driver but even though I now drive it very seldom, when I do, the brakes feel normal and familiar.
Wouldnt trade them for disks ever.

[Jimbro727]

Thanks for the replies!

I've spent the last few hours troubleshooting this with a buddy. Here's what we discovered:

• Using an SSBC brake pressure gauge, the front brakes read no pressure until the pedal is almost at the floor (maybe an inch from the floor), then in its final bit of travel, it starts to read some pressure.
• If we stabbed the pedal, we got more pressure - around 500PSI. If we slowly depressed the pedal, we got less pressure, sometimes around 250psi.
• We plugged the M/C ports and tried depressing the pedal, and it was as hard as a rock. We took that to mean that the booster and M/C are fine (no air, no internal leaking) - is that a correct assumption?
• The metering valve pin on the combination valve appeared to be sticking out more than we'd expect (it wasn't flush). We read that when pressure bleeding, it can cause the combo valve to cut off one of the circuits. We couldn't push the pin back in, it just popped right back out. I read somewhere to press it in as the brakes are bled, so we tried that, but as soon as we pressed the pedal, fluid shot out from the metering valve. We didn't do that again .
• We bled the front brakes. We kept getting bubbles from the front left, and got solid fluid from the front right. I feel as though there may be more air in the front left, because after letting it sit for a few minutes, we pulled more bubbles. As John said, maybe it's just air?

So what does that sound like to you guys? We feel confident we've isolated the problem to after the M/C. We think it could be an issue with the combination valve, or the rear brakes. We haven't bled the rear brakes yet - it got too late. Could air be the sole cause of these problems? The fact that the pressure gauge reads 0 until the pedal is almost floored makes us think it's not air, but we could definitely be wrong.

[Jimbro727]

Very frustrated update

I put my pressure gauge on my back right wheel, and I get 500PSI when the pedal is near the floor - just like the front brakes. The pressure also decreases around 50-100PSI, slowly, while the pedal is being held. That sounds like a leak to me, but I don't see any leaks. After pumping the pedal, we got around 550PSI. One time, while depressing the pedal extremely slowly, we got no pressure when the pedal was on the floor (combination valve cutting off the rear brakes?). There's probably some air in the rear lines, but could that cause this problem? Even if that accounted for the 300PSI I'm missing from the rear brakes, what's going on with the front? I've bled them quite a bit. I'm not so sure this is air, since the problem existed before I replaced the lines, when I had bled the brakes numerous times.

Does anyone have any clue what could be wrong here? Frustrated doesn't even begin to describe me right now. It's gorgeous outside, and I just want to drive my car. I'm a click away from ordering an SSBC kit and hopefully being done with all of this. I didn't really want to spend the money on that right now, but at this point, if that's what it takes for me to drive my car this summer, then that's what I'll do.

Anyone?

[chipster]

Yes, if you get a hard pedal with the master cyl. plugged, you can eliminate the master cylinder and booster as the problem. So you either have:
(1) A leak
(2) Air in the system
(3) Rear brakes not adjusted properly or not assembled properly.

Just a thought, are the bleeder screws on the calipers on the TOP of the calipers? If they were put on the wrong sides, they would be upside down, the bleeder screws would be on the bottom, and they would never, ever bleed correctly.

[HWYSTR455]

And which hole on the pedal is the booster rod? Maybe try the top one.

I've seen weird problems like this due to boogered prop valves.

You say the fronts don't see pressure until the final travel of the pedal? That to me sounds like you've got the front & rear lines mixed up, either at the master or at the prop valve.

Hitting the pedal fast and getting better pressure sounds like a booster issue.

Ditch the prop valve, use a 'T' for the fronts, and put a adjustable in for the rears. There's just no reason to use the old style prop / dist block valves anymore. No worry about it hanging, and you control the distribution..

If you see air, keep going. The driver front is the shortest distance, you should be able to bleed that one easy and quick.

.

[Jimbro727]

Originally Posted by chipster

Yes, if you get a hard pedal with the master cyl. plugged, you can eliminate the master cylinder and booster as the problem. So you either have:
(1) A leak
(2) Air in the system
(3) Rear brakes not adjusted properly or not assembled properly.

Just a thought, are the bleeder screws on the calipers on the TOP of the calipers? If they were put on the wrong sides, they would be upside down, the bleeder screws would be on the bottom, and they would never, ever bleed correctly.

1) certainly sounds like a leak, but I haven't been able to find it. I've checked and rechecked every connection. There's also no fluid on the floor, and the level in the m/c reservoir doesn't go down.

2) I spoke with someone at inline tubes today, and that's what he thought. I asked him if he thought it could be the combination valve, and he said he thought it sounded like air. He said I need to bleed, let it sit, and bleed some more. I'll spend the next few days seeing if that helps at all.

3) I'm pretty sure that the rear brakes are assembled properly. I've rebuilt drum brakes before. The parking brake works, and I can hear them actuating when I press the pedal - also, the pressure is still low in the back, and assembly wouldn't cause that.

The bleeder screws are at the top of the calipers. I've read enough forum posts to know not to make that mistake

Originally Posted by HWYSTR455

And which hole on the pedal is the booster rod? Maybe try the top one.

I've seen weird problems like this due to boogered prop valves.

You say the fronts don't see pressure until the final travel of the pedal? That to me sounds like you've got the front & rear lines mixed up, either at the master or at the prop valve.

Hitting the pedal fast and getting better pressure sounds like a booster issue.

Ditch the prop valve, use a 'T' for the fronts, and put a adjustable in for the rears. There's just no reason to use the old style prop / dist block valves anymore. No worry about it hanging, and you control the distribution..

If you see air, keep going. The driver front is the shortest distance, you should be able to bleed that one easy and quick.

The booster rod is currently on the lower hole, which I thought was correct. Within a half an inch of pedal travel, I can feel the M/C piston being depressed, so I think that's all correct. Is it possible that I have it in the wrong hole? Is the upper hole always for manual brakes?

Do you think a brand new prop valve could cause this?

I'm pretty sure that the front/rear lines are correct - as much as I'd like it to be something easy like that. The port closest to the firewall goes to the inlet on the top to the right (facing the firewall) of the combo valve, the port closest to the front of the car goes to the inlet on the top and to the left of the combo valve (facing the firewall).

I keep coming back to the booster - because I recall the pedal feeling different before I replaced the booster, but I stupidly replaced the M/C and something else (I can't remember now) at the same time as the booster, so I wasn't sure which caused the change. Could a bad booster cause an issue like this? It seems to function properly otherwise - the pedal is hard when it isn't getting vacuum, and light when it is (but still softer than I'd expect in both situations).

I might end up ditching the combination valve for a setup like that if lots of bleeding doesn't help. I figured if I replaced everything with the same parts that were used in '78, I wouldn't introduce more variables, and everything would work...


Thanks again for the info - I'll let you guys know how the bleeding goes. I did get some air out of the back right, but not from the back left. (I guess that makes sense if the air was farther upstream?).

[HWYSTR455]

Originally Posted by Jimbro727

I'm pretty sure that the front/rear lines are correct - as much as I'd like it to be something easy like that. The port closest to the firewall goes to the inlet on the top to the right (facing the firewall) of the combo valve, the port closest to the front of the car goes to the inlet on the top and to the left of the combo valve (facing the firewall).

I'm not following on this one. Any chance you can post a pic? And yes, a brand new prop valve can be bad very easily. Seen it several times.

The lower hole on the pedal is correct for power, but figured it might be worth a try. Leave it if that's the way it's always been, and look elsewhere for a 'problem'.

You're still getting air? Can't really go much further in troubleshooting until all the air is bled out. Could still be your culprit...

.

[78 GHOST]

I apologize for not reading the entire thread, however I wanted to post some info in the following link that you might find useful.

http://forums.maxperformanceinc.com/...89#post3707789

Good luck.

P.S. If anyone wants me to fabricate a similar setup, you only need to ship me your old M/C cover and (2) male air fittings of the style you want to use. I'd be happy to weld up one of these for anyone interested.

-Matt

[Jimbro727]

Originally Posted by HWYSTR455

I'm not following on this one. Any chance you can post a pic? And yes, a brand new prop valve can be bad very easily. Seen it several times.

The lower hole on the pedal is correct for power, but figured it might be worth a try. Leave it if that's the way it's always been, and look elsewhere for a 'problem'.

You're still getting air? Can't really go much further in troubleshooting until all the air is bled out. Could still be your culprit...

.

As I was typing that, I was thinking it was too confusing to not post a pic - I'll post one today.

That is the hole it's always been on, but then again, the brakes haven't worked properly since I bought the car..

I got some air, but that's because I had opened the lines since the last time I bled. I have bled this until there was no air and still had the problem. I'm going to bleed more today, and see if I get more air, and report back. Last night when I was checking the pressure at the driver's side front caliper, I was getting virtually no pressure - around 50psi or less, and when I depressed the pedal with the M/C cover off, I saw a few bubbles come from the rear reservoir. I take it that means air some how got back in to the M/C? I'll bench bleed it again today...

[Shiny]

Jimbro - any updates?

I was looking for more info and ran across this post.

I am also so frustrated with this same symptom I have a hard time working on it anymore and my car is just sitting.

I also have a new brake system, front to back, and have bled repeatedly as you, vacuum, pedal pressure, after sitting for a day, etc., with no improvement.

I have a new combo valve and new master from Inline Tube.

This weekend, after talking with Inline Tube, I fabricated plugs for the master, thinking I may still have air in it, but when plugged, the pedal was rock solid as soon as the slop in the rod was taken up.

I pulled the rear drums off and do not see any problems with my assembly.

Did you ever get an answer about residual pressure in the rear line? When I pulled my rear drums, I noticed "slop" between the pins and the shoes. This tells me there is no residual pressure in the cylinders. I would think the return springs should be pulling the shoes back against the cylinders, and if there was residual pressure, those pins should be tight against the shoes???

I will call Inline Tube and ask them about this, but I was hoping you were having better luck than me.

I think the basic symptom is caused by pressure building slowly in the rear lines, which is consistent with maybe a lack of residual pressure ?? My understanding of the combo valve is it will limit pressure to the front until the rear has pressure. My pedal goes nearly to the floor before the front calipers work, yet there ARE NO BUBBLES. This makes me think the root problem is lack of pressure build in the rear lines.

I wonder if the Inline Tube combo valve is supposed to have a check valve to hold residual pressure in the rear, and maybe it isn't working ?? Does anyone know ? What I have read is that the master for my original drum brake system had check valves built in, but the master for a disc system does not.... so how else can the rear get residual pressure if not from the combo valve? How can I check to see if this is working?

I will try adjusting the rear shoes until they are too tight and see if this makes a difference. Maybe my new shoes are just moving too far still ??

Should I buy a residual pressure valve for the rear line ?

How can something seemingly simple be so difficult ??

[ericwy]

In another thread from 2006, 71firebird400 chased a braking problem for months and had replaced everything in the end it appears it was the tension on the brake rod adjustment was too tight.

71firebird400's " Brakes don't work well" thread : http://forums.maxperformanceinc.com/...d.php?t=465821

Relevant replies from that thread:

Originally Posted by sts

<snip>
...
I mentioned it back at the begining and I think that other people have mentioned it. Have you checked the tension on the brake rod? You haven't mentioned the results of this test, I'm not a mindreader, so I can only guess that you haven't tried this troubleshoot.

It needs zero lash, meaning almost/slightly flopping around. If there is enough pressure on the rod, it causes the m/c cups to cover the residgual port, a hole that allows the fluid to bleed off pressure when you let off the brakes. Covering the residgual port will give symptoms as you describe.

If you have actually loosened the rod until it slightly flops around, and it doesn't solve the problem, you can rule out this as a problem. But unless you actually loosen up the rod until it flops around, you cannot be positive that this isn't the problem. In the many years of being a proffesional mechanic, the biggest problem I have seen with professionals and amatures is that they do not troubleshoot with a go/no-go. You cannot say that's okay. You have to actually test setting it up with before change and after change. If you don't use that approach always, you're pissing in the wind, something that a lot of professional mechanics do because they will not take the time to verify correct operation of components.

Maybe an idiot would have a problem with setting the rod so that it flops around, but you show an abundance of common sense, so you probabally understand the definition of zero loas plus slop. If the rod is set at zero lash with slop, it cannot fall out. If you haven't tried it, you cannot rule it out as not causing the problem. Loosen the rod until it flops around and test the brakes. If it doesn't slove it, set it back where it was. If it solves the problem, and you cannot stand the thought of the rod flopping around, tighten it up some until the point just before it causes the hard pedal.

Originally Posted by 71firebird400

Good News! I adjusted the brake pedal to have a little bit of slop and took the car out for a test drive. After about 3-4 blocks I noticed the brakes really starting to get stronger; now the car will skid the rear wheels (although the left locks up before the right; but thats another issue I'll have to work out). Overall the brakes improved quite a bit; now I want to bleed the system one last time and possible replace the front calipers; the reason being that with the brakes improved so much I notice things I couldn't before (the car wanders just a slight amount under heavy stopping). I would like to say THANK YOU to STS, Scarebird, ScottK, and anyone else who contributed! It's amazing that you guys stuck with it over the past months getting this thing figured out.

Mark

[Jimbro727]

I just realized that I dropped the ball on this thread..

I was supposed to post a picture, but then I was working on the car that night, bled a lot, then noticed some bubbles coming out of the M/C when I depressed the pedal. I got really discouraged and then busy with work, and haven't touched it since then. I'll try to get out there this week/early next week to put some more work in to it and take those pictures.

I assume the air got in to the M/C when I was trying to bleed manually (two people - one pressing the pedal, another opening the bleeder). My issue with that method, is that the lines coming out of the M/C make a steep turn down to the combo valve right after the M/C. When you depress the brake pedal, you push fluid through this line, and relieve the pressure at the bleeder valve. But I would think the air in the line will naturally move up to that bend right next to the M/C. When you release the pedal, you then suck that air back in to the M/C. At least, that's what I think happens..

I'll just stick to pressure bleeding..

Originally Posted by Shiny

Jimbro - any updates?

I was looking for more info and ran across this post.

I am also so frustrated with this same symptom I have a hard time working on it anymore and my car is just sitting.

I also have a new brake system, front to back, and have bled repeatedly as you, vacuum, pedal pressure, after sitting for a day, etc., with no improvement.

I have a new combo valve and new master from Inline Tube.

This weekend, after talking with Inline Tube, I fabricated plugs for the master, thinking I may still have air in it, but when plugged, the pedal was rock solid as soon as the slop in the rod was taken up.

I pulled the rear drums off and do not see any problems with my assembly.

Did you ever get an answer about residual pressure in the rear line? When I pulled my rear drums, I noticed "slop" between the pins and the shoes. This tells me there is no residual pressure in the cylinders. I would think the return springs should be pulling the shoes back against the cylinders, and if there was residual pressure, those pins should be tight against the shoes???

I will call Inline Tube and ask them about this, but I was hoping you were having better luck than me.

I think the basic symptom is caused by pressure building slowly in the rear lines, which is consistent with maybe a lack of residual pressure ?? My understanding of the combo valve is it will limit pressure to the front until the rear has pressure. My pedal goes nearly to the floor before the front calipers work, yet there ARE NO BUBBLES. This makes me think the root problem is lack of pressure build in the rear lines.

I wonder if the Inline Tube combo valve is supposed to have a check valve to hold residual pressure in the rear, and maybe it isn't working ?? Does anyone know ? What I have read is that the master for my original drum brake system had check valves built in, but the master for a disc system does not.... so how else can the rear get residual pressure if not from the combo valve? How can I check to see if this is working?

I will try adjusting the rear shoes until they are too tight and see if this makes a difference. Maybe my new shoes are just moving too far still ??

Should I buy a residual pressure valve for the rear line ?

How can something seemingly simple be so difficult ??

Well, here's the good news: You have the exact same problem as me! Your symptoms sound identical to mine.

I don't believe I got an answer to that residual pressure question. I would have hoped that inline tubes would have mentioned that when I called them, specifically asking them about the combo valve - but they may not have. I asked them if it's possible the combo valve could be causing these symptoms, and he said it sounded like air in the lines. This would be my second new combo valve (first was from yearone), so I assume that's not my problem. Then again this is also my third or fourth m/c (I lost count..). Logic would tell me that the issue is somewhere else - I'm just not sure where - or I'm just really, really unlucky..

I'll put some more work in to it this week, and post back. Let me know if you make any progress. I can't tell you how nice it is to know that someone else is having this problem, so I don't feel like a complete idiot..

Originally Posted by ericwy

In another thread from 2006, 71firebird400 chased a braking problem for months and had replaced everything in the end it appears it was the tension on the brake rod adjustment was too tight.

71firebird400's " Brakes don't work well" thread : http://forums.maxperformanceinc.com/...d.php?t=465821

Relevant replies from that thread:

Thank you - I'll certainly look in to this, but if I understand correctly, he's saying that the rod could be adjusted out too much, causing constant pressure on the M/C. If that's the case - it's not my problem, because I have to depress the brake pedal a bit before I feel any resistance from the M/C, so I know it's not constantly applying pressure to the M/C piston.

[HWYSTR455]

Residual pressure valve, lemme take a shot at that too. The only time I know of that a residual valve is used is when the master is below the calipers or wheel cyls. Can rule that out.

Still would like to see a pic, post one when you can, k?


.

[78 GHOST]

A short story:

When I disassembled the GTO to perform the frame-off, there was no "hold-off" or residual pressure valve installed. According to the shop manual, this valve (if installed) would have been installed at the rear crossmember, joining the long section of brake line with the section that leads to the differential.

In my case, all I had was a coupling (female to female) made of brass with a hexagonal shape to the body of the coupling. I set this aside and promptly forgot about it. Fast forward to reassembly, I decide I need this residual pressure valve, as it's in the manual, etc. and proceed to purchase one from Inline Tube.

I had some problems bleeding the brakes but eventually got things worked out. I never could seem to get the brakes to act "right" in the shop. I couldn't seem to get the rears to let go after bleeding and testing the brakes. In my enthusiasm to get things on the road, I ignored what I knew to be wrong and trust that it would work out on the road.

Well, as I drove the car the first time, it seemed a little sluggish and just didn't seem to want to roll. I pulled up a slightly inclined driveway and noticed the car happily staying put. Well I drove home slowly (about 2 blocks) and used an IR gun to shoot the rear drums.. they were scorching, close to 300 degrees.

I pulled the car apart and determined the adjusters were way loose until you pressed the brakes for the first application, then the rears remained fully activated.

I wondered if I had installed the residual valve backwards, nope.. I turned it around and checked, same problem. Eventually I wised up and removed the expensive residual valve and reinstalled the coupling I originally removed.

After replacing everything in the rear drums, and adjusting the shoes, I flushed and bled the system and tested it OK in the shop.

I test drove it and everything has been 100% perfect since then.

I'm convinced this valve is a complete piece of 5hit.

I hope this helps anyone cursed with one of these things in their car.

-Matt

P.S. call with any questions (281)788-9554

[HWYSTR455]

Heh-heh! Great story! Not the valve's fault, it's the individual(s) who wrote the manual! Who, I might add, wouldn't particularly be the engineers! heh-heh! They probably cut and pasted from a 50's manual!


..

[Jimbro727]

Thanks for the story Matt! I guess I can rule that valve out as a possible problem!

I attached the pictures (finally). I apologize for the quality - I took them from my blackberry, because my family has had some bad luck with cameras recently, and both of ours are broken.

Please let me know if you'd like pictures of anywhere else, or more detailed shots of anything. Definitely let me know if you see anything wrong.

Thanks!

Jimmy

[Jimbro727]

bump..

anyone.. anyone?