Baffled by brakes

[diesel_lv]

1967 Coronet, did front disc conversion using Dr Diff. Kept manual brakes. Used air bleeder to draw a vacuum n bleed from passenger rear, driver rear, passenger front, driver front until no air and all nice clean clear brake fluid. Pushed pedal and it went to floor. Pumped it a couple times and firm as can be. Now been driving it, trying to work out engine, fi, etc.. bugs and brakes started getting mushy. Then almost to the floor. I bleed them again and the brake pedal did the same thing. To the floor, pump a few times and very firm. I found no sign of leak at rear cylinders, any connection point, distribution block, master cylinder. Anyone have any ideas on this? Thanks

 

[493 Mike]

1967 Coronet, did front disc conversion using Dr Diff. Kept manual brakes. Used air bleeder to draw a vacuum n bleed from passenger rear, driver rear, passenger front, driver front until no air and all nice clean clear brake fluid. Pushed pedal and it went to floor. Pumped it a couple times and firm as can be. Now been driving it, trying to work out engine, fi, etc.. bugs and brakes started getting mushy. Then almost to the floor. I bleed them again and the brake pedal did the same thing. To the floor, pump a few times and very firm. I found no sign of leak at rear cylinders, any connection point, distribution block, master cylinder. Anyone have any ideas on this? Thanks

Did you use a new master cylinder? Bench bleed it?
Mike

 

[vance.dykes]

it is sucking in air from the rear of the master . wont see any leak from that . if you have rear drums the wheel cylinders can do this also.

 

[hunt2elk]

Sure sounds like you still have some air in the system.

 

[Billccm]

Okay when you bleed after a spongy pedal do you see bubbles? If so, what particular line has the bubbles? I spent 6 weekends chasing what you describe and it was a bad flare. I had no fluid leaks whatsoever.

 

[slimt]

I wonder if its the inside bore size of the cylinder causing that issue. I thought for a manual brake it was suppose to be a 7/8 bore size for pressure? I had to do that with my 55.

 

[diesel_lv]

Did you use a new master cylinder? Bench bleed it?
Mike

Yes, new master cylinder from Dr Diff. N yes, bench bleed.

 

[diesel_lv]

Okay when you bleed after a spongy pedal do you see bubbles? If so, what particular line has the bubbles? I spent 6 weekends chasing what you describe and it was a bad flare. I had no fluid leaks whatsoever.

When I re did it yesterday, I saw bubbles in all the lines. But the fluid level was up. I bleed w the air bleeder until no bubbles at each wheel. Well that sounds like fun, checking every flare. Or as above, possibly air bleeding in from back of master cylinder. Is there a way to check/test? Since no fluid coming out

 

[vance.dykes]

When I re did it yesterday, I saw bubbles in all the lines. But the fluid level was up. I bleed w the air bleeder until no bubbles at each wheel. Well that sounds like fun, checking every flare. Or as above, possibly air bleeding in from back of master cylinder. Is there a way to check/test? Since no fluid coming out

WHEN I DO THIS I STAY ON SIDE ROADS ONLY!!!!!!
i would take a brake hose clamp put on the rear brakes as to take out that part of the system then do what is needed to drive carefully only hafe of the brake system and see if the pedal drops. then i will move the clamp to the right front then the left. this will help isolate to find bubbles. checking all flares take your line wrench loosen and tighten 2 or 3 times a little tighter each time this may help seat the flares.

 

[diesel_lv]

WHEN I DO THIS I STAY ON SIDE ROADS ONLY!!!!!!
i would take a brake hose clamp put on the rear brakes as to take out that part of the system then do what is needed to drive carefully only hafe of the brake system and see if the pedal drops. then i will move the clamp to the right front then the left. this will help isolate to find bubbles. checking all flares take your line wrench loosen and tighten 2 or 3 times a little tighter each time this may help seat the flares.

It took about 300 miles of short daily drives over a month to get spongy.

 

[Billccm]

When I re did it yesterday, I saw bubbles in all the lines. But the fluid level was up. I bleed w the air bleeder until no bubbles at each wheel. Well that sounds like fun, checking every flare. Or as above, possibly air bleeding in from back of master cylinder. Is there a way to check/test? Since no fluid coming out

Bubbles in all lines is probably something else. I had bubbles at the left front only.

 

[65wgn440]

If you are definitely not losing any fluid, then I would warranty/replace the master cylinder.

 

[vance.dykes]

It took about 300 miles of short daily drives over a month to get spongy.

then i would go over all flare line nuts and see what happens if it returns then i would replace master cylinders. and don't get a rebuild get new i have had so many bad out of the box or fail in a week .

 

[bm02tj]

WHEN I DO THIS I STAY ON SIDE ROADS ONLY!!!!!!
i would take a brake hose clamp put on the rear brakes as to take out that part of the system then do what is needed to drive carefully only hafe of the brake system and see if the pedal drops. then i will move the clamp to the right front then the left. this will help isolate to find bubbles. checking all flares take your line wrench loosen and tighten 2 or 3 times a little tighter each time this may help seat the flares.

If any one puts a clamp on one of my brake hoses they have to replace as it can damage the inner liner
I would never use one unless I had no other option then replace hose asap

 

[khryslerkid]

Hows your rear shoes adjustment? Too much travel can put the brake pedal close to the floor.

I've never found any of these bleeding devices to work like they should. Ever time I hear of someone having problems with air in the lines they say they are using one.

To do this by yourself...Use a glass bottle and a piece of long hose to fit on the nipple. Have some brake fluid in the bottom of the bottle so the end of the hose will be submerged and not suck any air. Brake the nipple loose and give the pedal two or three slow pumps. Then tighten the nipple. Check the level in the master cylinder after each wheel.

Right rear, left rear, right front, left front.

Are the bleeders on your front calipers at the top? Some installations will have the bleeders at the bottom and you'll have problems bleeding.

 

[vance.dykes]

If any one puts a clamp on one of my brake hoses they have to replace as it can damage the inner liner
I would never use one unless I had no other option then replace hose asap

as a 40 year experience master a s e tech if you know the right tool and how to use them there will never be a problem.

people ask for help and all some of you want to do is tear people up for your lack of knowledge.

 

[bm02tj]

as a 40 year experience master a s e tech if you know the right tool and how to use them there will never be a problem.

people ask for help and all some of you want to do is tear people up for your lack of knowledge.

The problem shows up a year or so later
So I still know it is wrong to pinch brake hoses

 

[Frankb]

Make sure the bleeders on the new calipers are pointed up. As straight up as possible.

 

[vance.dykes]

The problem shows up a year or so later
So I still know it is wrong to pinch brake hoses

1. this in a test in repair manuals and snap on and other tool maker sell the brake line clamp if you did this for a living you might understand.
2. your complaint of it will take a year tells me that it is air sucking in to the system.
it will be hard to tell exactly what with out isolating one component from the system to know exactly the part failure.