Getting my *** handed to me.. these damm brakes
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I have and am chasing a similar issue. Air getting in. But no fluid leak out. I have read that this is possible with brake cylinders and/or master cylinder. Mine has the front disc brakes disk. And rear cylinder drum breaks. I read that it's possible the cylinder of either master or cylinder to move past seal protection that can allow air in. But once pressure is applied close to prevent fluid leakage? That this occurs using break cylinders or master cylinders that have been rebuilt perhaps one too many times?
I know it's throwing darts as speculation. But makes some sense?
I know it's throwing darts as speculation. But makes some sense?
No. The offset bracket the OP is using is a different story. But a regular 4 to 2 bolt adaptor works just fine with the standard manual brake push rod. I have a stock manual brake rod and a 4 to 2 adapter from DoctorDiff, with one of his master cylinders.
It is possible for the master cylinder to leak internally. If the seals are bad it can create a situation where you never get a hard pedal. Like I mentioned earlier, I had a brand new master cylinder that was bad straight out of the box, no amount of bleeding solved the issue. I replaced it and everything was fine.
Now, whether or not that’s your issue or the OP’s issue is a different story. But it’s possible.
But like OP. Bleeding alone doesn't fix. Or in my case. Doesn't fix for long. It progressively gets worse. Something is certainly sucking? (Sorry for the pun)
Right. If the seals in the master cylinder are bad or not seated correctly the fluid can just be exchanged between the ports or chambers. Pressure can be lost as it starts to build if it goes past the seals, pedal stays soft even though no air comes out of the system. You can’t build pressure in the lines if the seals around the piston are leaking badly enough.
In the OP’s case he didn’t bench bleed the master cylinder, so there may be air trapped in the master cylinder keeping it from building pressure. Or it could be faulty seals in the master cylinder. Assuming that the rest of the system was bled properly as described and there’s not air trapped anywhere else. But you and the OP may have different issues.
I think it is.
That is what I'm thinking. I have a manual Wilwood aluminum master cylinder that was targeted for a different build that has stalled a bit. I'm going to bench bleed and try on my B-body break issue. It's a superior component. But doesn't have the stock desired look. But it's something I can try fast. I will certainly post results and observations.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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The hydraulic system is a sealed system. Or should I say is supposed to be.
>If fluid is not getting out, then air cannot get in; unless the diaphragm under the cover is not sealing..
>If the liquid level in the M/C is not changing, then you are not losing fluid.
>If the liquid level is changing rapidly with no visible sign of leakage, it may be going into the booster.
> If the pedal is not staying hard, then, here are some possibilities;
1) the rear shoes are going out of adjustment; usually because the self-adjusters have failed or because you never back the car up, lol, which is what makes the automatic adjustment, lol.
2) the rear hose has gone soft
3) you have a mechanical problem
4) you are boiling the fluid; usually from dragging pads, two-foot driving, or just a big old boot hanging up on two pedals at once.
5) the M/C is defective. This one you can sometimes feel. pump the pedal hard and just hold it there. if the pedal starts sinking, badaboom!
> if your pedal, upon application, is getting closer to the floor over time then,
your rear brakes are going out of adjustment . BUT
> if your pedal is just hanging lower to the floor over time then; the compensating ports are not working, usually because the pushrod is too long. These ports are clever little devices. When you apply/lift-off the brakepedal, the fluid goes out and returns. But it only goes down the pipes a couple of inches. As the pads and shoes wear, the fluid has to go out a lil further, over time. Eventually, your pedal would be so far down, that no braking could occur. So the designers introduced tiny ports at the top of the system, to compensate for this. Therefore, about the first inch of pedal-travel, nothing is going on down by the slaves, until the pistons get past the ports.
study this illustration for a minute. Notice that the two pistons are not physically connected. Once bled they are hydraulically coupled. The frontmost chamber (on the left in this drawing) goes to the rear brakes. So when you step on the pedal, the pushrod moves the rear piston, which then moves the hydraulic coupler, which then drives the front piston. If the car has drums in the back, it will usually have a "Combination valve or a proportioning valve", which is just a spring-loaded hold-back valve. In either case; the piston-pair will move along until one of several things happen
1) if the hold back is holding, fluid will want to go out to the calipers, but pressure will not build yet, cuz the the entire coupler is just sliding
2) when the hold back lets go, the fluid will then go out to the rear shoes. During this time, the rearmost piston is just sliding on by the frontbrake port
and NOTHING is going on at the discs. When the front piston stops moving because the shoes have hit the drums, THEN the fluid goes out to the calipers. And BOTH systems are now proportionally controlled.
3) if the rear brake-system should fail, then the frontmost piston will slide to the front of the bore and park there, but the rear-piston/front-brake system will continue to function, allbeit with a lower pedal.
4) if the front-brake system/rear chamber should fail, fluid may get pumped out the front line, but the mechanical extension on the front of the rear piston will still activate the rear brakes via the frontmost piston, but the pedal will not return to the top. Since the reservoirs are isolated from eachother, the rear brake system will continue to function, even tho the other reservoir has gone dry.
5) when you release the pedal; the rear-brake return-springs drive the fluid back into the reservoir, at the same time as "seal-retraction at the calipers does. This returning fluid enters the chambers in the M/C, and simultaneously the pistons are returned to their designated parking spots by the piston return-springs, which then uncovers the Compensating ports which then normalizes the whole system, ready for the next application. Because the whole system is sealed, all these things happen simultaneously; but the rear return-springs are the driving force...... until hold back is once-again established at the P-Valve/C-Valve.
6) If the fluid-level is properly maintained in the reservoirs, then there is no place for air to get suctioned into the system. At the rear, the Dual-Braking System that uses a hold-back valve is under a constant minimum psi, never less than atmospheric, even if you pull the residual valve out. And at the front, there is no way that those piston seals would ever allow it. Inside the reservoirs, there is never a time when suctioning can happen, except during bench-bleeding; and even then, she really doesn't generate much suction.
7) so if you are losing fluid, it is going somewhere! and
8) if you are getting a change in pedal hardness, AFTER, it once was hard,( like the day after,lol) more than likely it will be traced to a mechanical problem, or boiled fluid, which itself could point to a mechanical problem like seized sliders.
9) in any case; C-clamping the slaves will prove your hydraulics in mere minutes, NOT HOURS of PITA fiddle-farting around.
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1969cudarebuild
Active Member
I had the very same issue and found that there is air ttapped in the calipers. What I did was removed the calipers (the fronts) put some wood in to act as the rotar then made sure the bleeder valve was straight up. Once we did that and started doing the pedal pumping and cracking the bleeder all kinds of air come out. Brake pedal and function come right around. Make sure you bleeders are as straight up as you can get them. Sometimes it takes doing just as I did. Good luck.
plumkrazee70
Well-Known Member
Any updates?
boosted
Life Needs Air
No updates so far as I had to have eye implants yesterday. I have to drop the rear-end out of the car, ladder bar big tire car to get the wheels off and just cannot do it at the moment.
FWIW...I had the same issue. 4-piston K-H disc's up front with drums in the rear. No amount of bleeding helped...pedal always went to floor even though I was getting no aur out of the rears. Changed the rear wheel cylinders to new and....bingo, I quickly got a hard pedal. Not sure if the rear cyls were sucking air on pedal release or what but the new ones solved the issue.
Good luck 'cause it's little problems like these that stop you dead in your tracks!!
boosted
Life Needs Air
I have had Eye surgeries since 2010... So If I can share any info with you please let me know. This was just a new way.
boosted
Life Needs Air
Well i bled the m/c and now have a good pedal. I will go back out today to see if the pedal held or has it went backk to the floor overnight. I really appreciate all the help and thank everyone of you.
I bought a brand new master cylinder for my 70 Dart, factory discs. It sat for 12 yrs in a dry garage without the plastic plugs to cover the the holes . I dont what happened but it would not bench bleed even with the return hoses. I bought another one. Problem fixed.
Possible internal rubber pieces deterioation, or dried out ???
Possible internal rubber pieces deterioation, or dried out ???
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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My first M/C on the Barracuda was a 25 year old unit that I rebuilt. I pulled it out of a 5 gallon pail and gutted it, Physically there was nothing wrong with it. And it worked fine afterwards. But it was bigger than 1 inch, and I wanted to try a smaller one. I did not have one so bought a rebuilt which also worked fine. I liked it and it stayed on the car.
As far as I know, that first unit that I rebuilt, ended up back in the pail......
Some units are just particular about bleeding. I use clear hoses on the bench so I can see what is going on, cuz sometimes they need help. What I have seen is that the fluid just shuttles back and forth in the clear lines being sucked back into the master, instead of being replenished from the compensating ports. I just pinch the clear lines at the end of the downstroke before lifting. This forces the pistons to draw thru the C-ports. Problem solved. Once the compression chambers are purged of air, the lines no longer require pinching.
You probably just had one of those cranky buggers.
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I'm using the same GM calipers as the OP and had the same problem at first. For me it was a real fight getting the pistons on the calipers adjusted to the exact spot that they needed to be. Talking .003-.005". Once I did then the pedal firmed right up to where it should be.
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