Thread: Brakes - bled completely & pedal is still soft?

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Thanks guys!
Will let you know how it goes!

Ok,
front brakes are way out of adjustment(why the pedal stayed soft) and the rears were closer but, still not great. Working on that and will re-bleed. I did find through frame junctions in the brake lines (mentioned earlier)....what's the best way to get the air out of those little buggers?

Originally Posted by Mack57

Ok,
front brakes are way out of adjustment(why the pedal stayed soft) and the rears were closer but, still not great. Working on that and will re-bleed. I did find through frame junctions in the brake lines (mentioned earlier)....what's the best way to get the air out of those little buggers?

Mack,
If it were mine I'd get the shoes adjusted and see where you are. Through the frame fittings (the one's for boxed frames about 2.5"-3" end to end) are not a problem in themselves, but there were a bunch on the market a few years back that were machined such that they formed an air pocket in the middle that was just about impossible to get cleared out. Can't recall for sure, but I think they were a larger tube tapped on each end for AN fittings, and the large ID trapped air. I think Street Rodder did a tech article on them? Might have it in the barn stash of old mags, but not sure.

Yes Roger, Street Rodder did do an article about those frame fittings 4 or 5 years back I think. I don't think anyone still made them like those anymore but what would I know? Or if this is an older assembly, it could still have a set in there.

And I'll disagree on the adjustment making the pedal "hard". Air in the system will cause a spongy pedal. An out of adjustment set of brake shoes will cause a low pedal! These are 2 different issues.

Do the adjusting (front & rear) and re-bleed (front and rear). I would suggest adding a hose from the bleeder to a bottle and let the discharged fluid collect under the surface of some new brake fluid. This will prevent air being "sucked" back in should the assistant raise his / her foot before you close the bleeder and you can visually see if your getting air out of the system.

Lastly, is this with all new shoes? Are they high performance type? if so, have they been "bedded".?.?

Mack sinse you bought this with sytem already in place, you might want to remove the master cylinder and measure the stroke of the piston when you push it in all the way while being bench bled, then install and see if you get the same measurement at the rod when the pedal is pushed in, maybe a little short on the stroke which you never get the air out. Another questin arises, is this a dual master cylinder and are the front brakes connectd to the rear port and the rear brakes connected to the front port, are you running a factory style propotioning valve...? Also does this master have check valves in the ports...?

406 Rich, 34-40,
Today is a car day & hopefully will have some good news this eve. Never thought about the piston length.... Alright, time to get at it!

Not knowing what system you have, when they installed the booster/master some systems require that during install that the pedal pushrod be moved down 1.25 inches further down on the pedal arm, two reasons, alignment and it gives the rod alittle further travel, this means drill a new hole for the push rod. Just something else to consider..

Hey guys,
The cyl on the dr side is not working properly but, I did get some adjustment on it. Ordered 2 new for the front. The pedal is significantly better! Also, plumbed the booster vacc line & the booster is operational. I have not checked the rod length yet... Back to it. Thanks guys!!

Hi All,
Have been bleeding & re-bleeding these brakes....pedal still soft. The weird part being, the pedal has been VERY good at times only to be lost.... Using a Mityvac 8020 now and with bleeder open - Nothing but bubbles. What on earth am I doing wrong here?? 406 Rich, I will check that piston position but, I think I should have a consistent pedal even if it is low - yes?
thanks all!

I'm not familiar with the vacuum bleeder you are using, but if it hooks up to the bleeder screws, then the bubbles are the air being pulled past the threads on the bleeder screws. There are special bleeder screws available which will prevent this. Or, you can through - drill a bleeder screw, vacuum bleed that cylinder, then swap it out quick. Follow up with a quick standard pump - and - crack bleed, in case any air gets in the servo when you swapped out bleeder screws.

Yeah, I agree with firebird on this one, as I had the same experience with the vacuum bleeder. The fit of the hose on the bleeder is critical, and the instructions on the one I used warned that a small trail of bubbles would be from thread leakage. The drilled out bleeder is a pretty slick idea, but I'd say you've got a bad master cylinder. Nothing else explains having a good pedal, working fine and then the pedal going soft. You've got an internal problem on the MC seals.

Hey Huys, Thanks! I also gravity bled this AM and still no pedal..... Does that confirm the MC seals?

Originally Posted by Mack57

Hey Huys, Thanks! I also gravity bled this AM and still no pedal..... Does that confirm the MC seals?

It does in my mind. You also need to be sure that your pushrod adjustment allows the MC to fully retract with a small amount of free space, like less than 1/16" is OK but you don't want it engaged with the pedal retracted.

Thanks Roger, Will post how it turns out. Thanks,
Mack

I gotta agree with Rspears. If you can occasionally get a decent pedal, then it goes away. It sounds like the master is failing. Even if the shoes are out of adjustment, you should be able to get a firm pedal. Low, but firm. Once you adjust them then the pedal will be right at the top AND firm.

Hoping to hear good news soon!!