[Jimbro727]

Thank you VERY much for the responses, guys. It sounds like everyone's in agreement that I need to ditch these wheel cylinders in favor of some NAPA units. I'm going to order two, replace the passenger side, see if that helps, and if it does, replace the driver's side as well for peace of mind. I'm also considering buying a M/C from NAPA - does anyone think that the M/C could be causing some of these issues? After some googling, I've found a lot of people questioning the quality of parts from some of the chain parts stores (autozone, advance, pep boys, etc.). If my problems aren't solved by replacing the wheel cylinder, then I'll probably want to try bleeding the master again, in case I let some air in during all of this. If I do that, though, I think I'll just pick up a new one from NAPA (again for peace of mind), since it's the same amount of work as bleeding my existing one.

Originally Posted by chipster

I would NOT use the 2-man method to bleed the brakes, because you risk damaging the seals in the master cylinder, and it is just a major PITA. Power bleed or gravity only. I only use gravity.

That's fine, the 2-man method is annoying anyway, my only concern is that when you use alternative methods, you gloss over potential issues (like this one we're discussing here), since you're not using the brake system (really just the M/C) in the same way it is used when you're actually braking. Had I only used my pressure bleeder, I wouldn't have discovered this wheel cylinder problem.


Again, I can't thank you guys enough! I'll try to get to those cylinders this week/end and report back!

[PontGuy]

Just to be clear- I am not a Napa salesman! I just know that they carried the style wheel cylinders that worked for me while the other chain stores I checked here carried the ones that didn't work.

I would be willing to bet that your M/C is fine. But you are right that brake parts from the local discount stores can't really be trusted. If you read all the way through the other thread, you may remember that my rod was too long between the M/C and booster even though I bought them as a matched and assembled set. I figured that one out pretty quickly, but it took a while to chase down the wheel cylinder problem.

Whatever bleeding method you use, your pedal should firm up right away if the wheel cylinders are the fix. After bleeding what seemed like gallons through my brakes it only took a few minutes to get the system clear of bubbles after replacing the cylinders.

Walt

[Jimbro727]

UPDATE: I replaced both sides with NAPA wheel cylinders. After replacing the driver's side (where I was getting constant bubbles), it was a night and day difference. The brakes still weren't where I'd expect them to be, BUT it wasn't like having NO brakes. I then replaced the passenger side, and the pedal was either the same or a little worse. It's tough to gauge that sort of thing.

We then decided to start fresh and bench bleed the master. We got some bubbles. We then pressure bled the entire system, got some bubbles out of all four corners (expected). Pedal is still funky. The pedal isn't as firm as I'd expect, and no real braking power comes until the end of the pedal's travel. It just doesn't feel right.

While we had the master off, we decided to measure the booster rod. I'm not sure what we were supposed to be measuring, we pressed the pedal and measured how far it comes out, and it comes out just under 2". The rod coming out of the booster consists of a metal rod running through the middle of a larger cylinder. Both pieces move out and in as an assembly, but the smaller rod can be removed from the cylinder very easily. Is that how it is supposed to work?

Another note: I noticed that the pedal STOPS (reaches the end of its travel) a few inches from the floor. I can measure it exactly if needed. Is the pedal supposed to stop that early, or is it supposed to go down near the floor? With the M/C off, it drops down much more.


Any ideas? It's beautiful out and I need brakes!!

[PontGuy]

Sounds like some progress, but you still have air somewhere. After bleeding are you getting any bubbles from the rear with the new cylinders? With mine I always got small bubbles, almost milky, until I replaced the cylinders. Then with the new cylinders it stayed perfectly clear after just a few minutes of bleeding.

There should be just a little gap between the booster rod and the M/C, enough to ensure that the master retracts all the way. You can't feel this play with the pedal. I discovered that mine was too tight by watching the rear port inside the M/C through the fluid while tightening the mounting bolts. I put a couple of thin washers between the master and the booster and it solved my problem with that.

I think the pedal travel is limited by the travel allowed by the M/C and booster so the pedal may not actually reach the floor.

Also I would double check the fittings at the front to make sure they are not leaking. Getting the air out of the back may have increased the line pressure enough to create a leak somewhere else.

Walt

[67 LeMans 326]

I appoligize for not reading through this entire thread, but, did you install a new porportioning/distribution valve during this install? If so, are you aware that during the bleeding process if one of the resevores in the master cylinder happens to go dry, you will need to "reset" the valve? I found this out during my 4 wheel disc brake conversion. I could not get rear brakes at all, another friend could get rear but no fronts etc. In both cases we had installed new distribution blocks and they had to be reset.

In these new all in one combo valves that are on the market now, they have a safety backup built in, if one of the resovores in the MC goes low or empty, the valve shuts that resevore off and puts all the stopping power to either the fronts or rears whichever of the two did not go dry. Then, what you have to do is remove the sensor on top of the valve, push something thin down into the hole and it moves the internal saftey mechanism back to it's "home" position. I was told to use a straightened paper clip and beleive it or not, this solved all of my issues and bang, everything worked perfectly. Incredibly, this proceedure was NOT in the troubleshooting guide or instructions with my kit, I was given this info from the tech support line...

[Shiny]

Good info 67 Lemans 326...

Don't give up Jimbro !! Sounds like you are almost there...

I was told if the imbalance thing happened to loosen the front bleeders and push the pedal to try and "reverse" the pressure imbalance that tripped the switch the first time. This seems to assume the problem was pressure in front and not in the rear, which is a safe bet if the rears weren't working right.

My combo valve has a switch driven off the "imbalance piston", so if either system loses pressure, the brake light in the dash will come on. If the switch is there, you can put a meter or continuity light on it and see if it is making contact while the brake is pressed. This might be a good way to diagnose if the non-centered plunger is causing the problem. I think Walt had this problem and I don't know if he ever fixed it?

Walt - you still have your switch off-center? Maybe this will help? Also, didn't you have a tool (expensive paper clip?) to center the switch?

Also, there may be a pin protruding from the combo valve. My original manual said to hold it pushed in when bleeding. The support tech at Inline Tube, where I bought my valve, said this is not usually needed, but it may be another thing to try?

[PontGuy]

Yes, mine is still stuck but it is not affecting operation of my brakes. I have the '69 Inline Tube distribution block, not the later combo valve- I am not sure if that makes a difference or not. They look identical on the outside so maybe this "reset procedure" would work for me too.

How do you remove the sensor- does it just screw into the block?

With the original 69 block the switch would trip when you stepped on the pedal and the dash lamp would light, and then automatically reset when you released the brake pedal so the dash lamp would go off. My lamp does not go off. I have tried resetting the switch using a variety of methods without success. Since my brakes work perfectly my theory is that the switch is just stuck from all the messing around I did. But again, my brakes are working perfectly and I still have a long list of debugging work to do so the light hasn't risen to the top of the list yet. Trans pan leak, exhaust leak, that sort of stuff.

Jimbro, is your light stuck on? To be honest I am not sure why this would cause a low pedal but maybe another piece of the puzzle.

Walt

[goatsheadsoup]

I chased a sloppy brake pedal for years. I too replaced and double checked everything. I could bleed brakes with 3 or 4 different methods in my sleep. I changed master cylinders and wheel cylinders. I changed the brake lines. I adjusted and readjusted the brakes all over a 4 or 5 year period. I finally took a original brake booster and compared the rod length to the reproduction. The rod length was shorter and I machined a correct length rod on my grinder. The goat now stops on a dime with a firm pedal. The first time ( the last time) my wife drove it I saw the 68 going sideways when the brakes locked up. I pump them to avoid that. Even with silicone fluid it stops as good as the 2000 trans am (almost). I am so confident I would not even consider upgrading to disk brakes even with the 428, they are that good.

[Shiny]

walt - I replaced my aftermarket switch with an original.. been a while, but I think it had something to do with the connector. It is a threaded part, just unscrew to get access to the switch piston. I put a meter on my switch, and it never made contact, so I can't comment with any experience.

I would think the switch piston motion could be a matter of degree, though - maybe it can come on with the pedal pressed and then re-center as you described... but I think if there was a bigger differential, maybe it would get stuck like yours ??

I attached the combo valve diagram I pulled off the web again in case it might help.

I also added a picture looking down into the master through the fluid to show what Walt is saying about looking for the rod too long. If you look down into the drilled hole, you can see the piston in the master. If you watch this piston when you unbolt the master from the firewall, it will move (retract) if the rod is too long and has been preventing the piston from returning all the way when the pedal is released. It is an easy thing to check for, seems worth a shot ??

ghs - what do you mean by "sloppy pedal" you mean it went to the floor and you never had brakes? I think that is a new possibility that hasn't been given much thought in all of this. Any way to tell if the rod length is short if you don't have an original for comparison? Maybe looking in the master at the piston again, how much pedal travel before the piston moves??

[goatsheadsoup]

Interesting thread...By sloppy I mean pedal travel was too far, almost to the floor. I could not adjust it at the booster by turning the rod at the brake pedal enough to make much of a difference. You could experiment by rounding off a similar diameter bolt to the booster rod and taking off the master cylinder its only two bolts and would take a couple of minutes. Grind the bolt down to the length that makes your brake pedal travel satisfactory. I will use this method in the future to put the pedal firmness where I want it. I would of course make sure everything is correct first this is the brake system, we can't forget that but from now on I will check this as a regular brake item. These cars have been worked on for 40 years and different parts from different vendors and countries can make restoration a challenge.

[Jimbro727]

Thank you so much for the replies!

It sounds like we've got a few potential issues here:

Combination valve: I do not have my switch hooked up right now, if I remember correctly, I broke the end of it off taking off the combination valve at some point, so I need to replace it. I recall reading that when it's cutting one of the systems off, it grounds the pin - is that correct? I have a multimeter with a continuity tester, so I'd clip one probe to the pin on the combo valve and the other one to a good ground point somewhere (a bolt or something). That's how I was testing if the safety system was activating, and it never did. Can anyone confirm that that is the proper way to test it without the light hooked up?

M/C resetting: This is a simple one, and I'll look into it to make sure it's returning fully. (Thanks for both pictures Shiny!)

Booster rod length: This sounds like it could be an issue. Does anyone know where I can find what the proper length is supposed to be for my car? I don't have access to another booster, so my only recourse would be to replace the booster again and hope that one had the correct rod. goatsheadsoup, would you say your pedal felt like mine? Did it feel like the brakes were actuating, just not very well, and you'd have to floor the pedal to get the stopping power you should be getting pretty early on in the pedal's travel?

[MikeR64]

I tried to see if this had been addressed yet, and from what I can see it hasn't. You said the brakes had never been right since you bought the car. Way back when, the spazzoids in the shop where I worked would occasionally put the front calipers on the wrong sides. This would give the exact same symptoms you have; pedal really low, brakes kind of work, and if you bleed them about ten thousand times, you eventually get to the point where no more air comes out. The problem is, the air is still there in the top of the caliper and this makes the pedal spongy and kind of like yours is now.

They were famous for doing that on GM cars and this was back in the 70's. I don't even know if you can put the calipers on backwards any more, but you may want to check that out.

[PontGuy]

I still have my original '69 distribution block. It is really beat up but it always worked fine- it would light the dash lamp when I stepped on the brakes with one side of the system out, and then reset when I released the pedal. I guess I should remove the old brake lines and figure out how it is put together. The new one will just not reset.

Jimbro, yes you can use a meter to check the switch for continuity as you describe.

GHS, by booster rod length are you talking about the rod that attaches with the clevis to the brake pedal? I could see that being a problem if it is way off. But since the pedal stops before reaching the floor but the brakes are soft then its probably not Jimbro's issue.

MikeR, I don't think the caliper possibility has come up. But in the other post we did discuss mixing up the left and right drum adjusters on the rear brakes. That creates a problem since they will loosen as the brakes are cycled instead of tightening. I've seen that one done before.

Walt

[the-rookie]

So everything was new from inline tube? Thanks for the head up for the future.
Its obvious and its been said several times that you have a leak, somewhere. Any change after changig those rear cylinders?

[GoatGlider]

I've read this entire thread. Wow! Poor guy!

I have my own problems with my brake system - but compared to yours, I'm happy :-)

My thoughts:

Your combination valve is installed the right turn around (you asked that earlier?). The rear section of the MC is for the rear brakes and it is connected to that part of the valve that has one cylindric output (cylinder holds the residual valve I assume). The front section is for the front (disc) brakes and is connected to the part of the valve that has two outputs.

Air in the system? With no vacuum in the booster the pedal would feel soft with significant amount of air in the system. It's not hard to compress air. If pedal feels hard I would guess there is no air in wheel cylinders or elsewhere - or not enough to explain your problem. Only few bubbles make not enough room to let your pedal sink to the floor.

Hard enough pedal? Once you wrote, you can press the pedal (with no vacuum) to the floor with much effort - even if it feels hard. This I think should not be possible. It should feel exactly the same as with plugged MC.

And I agree that there is still something wrong with your brakes. With everything new it should be stiff and brake like hell.

The pressure your MC makes goes somewhere. If something would be blocked, it would be stiff but would not brake and that is not the case.

I would guess, it makes sense to play more with plugging things. Plug only the rear-brake-output of the combination valve - did you try this already??

Just asking: Did you also replace the rubber line connecting the rear axle to the system?

Good luck - you'll enjoy this years summer!!

[Jimbro727]

Sorry for the delay everyone, and thanks for the replies. Had more issues with my knee, work got busy, and life in general got in the way of my project Now I'm back working on it.

A couple of people had mentioned that the front calipers could be swapped - this is not the case, they're on right (I installed them myself). The bleeders are on the top (that's correct, right?).

Today I decided to start plugging different parts of the brake system to try and determine where the issue is. All tests were done with the engine off (so no assist from the booster). Here's what I found:

• I started by plugging the front system by pluggng the front outlet on the M/C. That caused the pedal to be rock solid. So I figured the issue is not in the rear system (valid assumption?)
• I hooked the M/C back up and then plugged the driver's side front outlet on the combination valve. The pedal went back to being pretty easy to press. So I figured the issue was not with that side.
• I then plugged the passenger side front outlet on the combination valve. The pedal remained soft.
• Plugging both sides at the combination valve should have caused the pedal to become hard again unless the issue was in the combination valve itself, so I plugged the front outlet on the M/C to verify that the pedal was still hard and it was NOT. The pedal was still easy to press. I'm wondering if I sucked air back into the M/C during one of the previous tests, what do you guys think?

That's where I'm at. If anyone could give me some input, that would be great. So far, I think I've determined that the issue is with the combination valve or is somewhere in the front system. If I did pull air back into the M/C during my tests, does that explain why the pedal is no longer hard when I plug the front outlet?

Thanks guys

[PontGuy]

Wow, still at it.

Actually I am glad this thread came back up. My car is all in pieces again- I pulled the engine out for work and then removed the windshield and dash and everything behind it for restoration. It would be an ideal time to try the "paperclip reset trick" since my block is now very easily accessible. Guess I first need to put the brake pedal assembly back in the car in order to test it though I did pull the top off my original block and looked down into it though. Not much to see.

I think that the danger of pulling and plugging lines at the combo valve is that if you get air in the system it could give you false readings. My suggestion- hook it all back up, bleed the system and then repeat your test- plug the front of the master and see if you get a hard pedal. But then if you do get a good pedal, reconnect the front and plug the back and see what happens.

Also check for continuity at the switch while you do this. If it does not trip the switch then something is wrong there, because you will only be putting pressure on one side of the system.

Walt

[HWYSTR455]

The more I think of this, the more I think you should ditch the combo valve.

Try running a 'T' for the fronts and block the backs, as a test at least, and see how the pedal feels. That would eliminate one variable, and you could isolate it to the booster or master at that point.



.

[Shiny]

Jimbro. Thanks for the update, sorry to hear you are still fighting this, but glad you are back at it because that means the less pleasant priorities are behind you.

When I went down a similar diagnostic path, I concluded I could not break a line without letting air in and needing to bleed.

If you opened any fittings and did not bleed again, I wouldn't trust any conclusion.

I started by plugging the front system by pluggng the front outlet on the M/C. That caused the pedal to be rock solid. So I figured the issue is not in the rear system (valid assumption?)

I'm confused by this. What do you mean by "plugging the front system"? How would that eliminate the rear system? Seems it would indicate rear system ??

And I'm not sure about the air in the master. If you plug only one outlet, I'm not sure you should expect a firm pedal. If you plug both, yes, but I am ignorant about the scenario you describe. I did plug both outlets in my master and pedal was solid, so I concluded my master was bled and not "bypassing" as some had suggested. I don't recall pluggin only one, so I just can't comment. I reconnected both outlets and bled again after that.

Walt says "start over" and I think he is giving you good advice. I think it is unlikely you sucked air into the master, but plugging it up is probably the only way to confirm. I suggest plugging both outlets on the master at once to start. This will give you confidence in the master before you move on.

But after verifying the m/c I recommend bleeding again before doing anything else.

I think there may also be diagnostic guages available, maybe you could rent one from the parts store ?? It may be a pain, but you could possibly get a direct measure at each wheel and reduce some confusion without breaking fittings at the combo valve ??

[chrisp]

Had a similar issue , no signs of leakage anywhere , turned out after i peeled the dust caps back from the wheel cylinders 1 was wet , remember no sign of any leakage . Was such a small leak pushing fluid out and then drawing it back in along with air upon pedal release . Inline tube asian wheel cylinders , got a set from Napa , made in US . wasted 3 days on and off . Been doing breaks for 25 years , 99% of the time when something is leaking you can see it .