Soft pedal after lots and lots and lots of bleeding.

[72 charger]

After finally getting my 8 3/4 installed in my 72 charger I naturally went to bleed the brakes. First I tried to gravity bleed them and after a while I got the fluid to press through and closed up all the bleeders after not seeing any bubbles for quite a while. Took the car out for a spin and the pedal was unbelievably soft. I came back and check all connections front and rear. Rear had some fluid so I tightened them down and tried again with the bleeding. Same result as before. Test ran again still very soft. Then tried to actually bleed them with someone pumping the brakes. Got no air out solid fluid. Checked connections again no leaks. Test run still very soft with the brake light coming on at various times not continuous. Today we again tried bleeding the brakes went over every connection once again and still the pedal is very soft. The only issue that we can notice is when you depress the pedal it seems the booster makes a squeaking noise almost. Like perhaps there is a malfunction in the booster? I'm not familiar with the booster innards. But im baffled as to why we cannot attain a hard pedal. Any suggestions?

 

[snakeoil24]

Seals in your master Cylinder are leaking past the piston.

 

[Cranky]

How old is the master cylinder? If you had a good pedal before then started bleeding and your pedal was being pushed further down than what it was going before the swap, you have have messed up a piston seal. Crud/rust (cast iron cylinder?) builds up in the cylinder over time and it can mess up the seal if you push it beyond that point.

 

[RustyRatRod]

Is the master cylinder mounted with the front up at an angle? If so, it's a PITA to get air out of it. You should jack the car up until the master cylinder is level and then bleed.

 

[72 charger]

So the MC is bad? The master cylinder is fairly new its a rebuilt one that I got from summit but not even a year old? With little use on it. Is there anyway to tell for sure signs of leakage anywhere or anything?

 

[67 coronet]

if you pull the master away from the booster.(no need to unhook lines)you might see fluid that has leaked out of the back of the master and into the booster.not always the case,but is something to check for sure.

 

[72 charger]

if you pull the master away from the booster.(no need to unhook lines)you might see fluid that has leaked out of the back of the master and into the booster.not always the case,but is something to check for sure.

If this is the case does the booster need replaced as well?

 

[Propwash]

I'd agree with RRR..Make sure she's level. Bigger deal than one may think. Use a one man bleeder or a chunk of aquarium hose into a soda bottle and pump those brakes. Not a fan of gravity bleeding at all. Pesky air up by the master or stuck by the prop/distribution valve can be a pain as well. I'll take the master cylinder over off and very very slowly press down on the brake and very very slowly let off the brake (too fast brake fluid will splash out into your engine bay) and watch for bubble's coming up through the brake fluid in the master. Usually always see some if a line has been changed out or removed. Plus it's another way for you to tell if your piston seals are junk in the master if it keeps on bubbling up in the reservoir, and you don't have leaks anywhere else.

Good luck.

 

[Cornpatch MO]

I am having the same problem with mine. It is a new Cardone re-built front disc and rear drum ( separate lines) Spongy pedal has just about got to be air in the lines being compressed. I think a bad MC seal would allow the pedal to go clear to the floor. Mine is simpler without a booster.
Tip I just read was to adjust the drum brakes till lock up and then bleed. I will try that. I tried gravity bleed with no success. I think somehow air is trapped in the line and it will have to be flushed out with alot of brake fluid. ........................................MO

- - - Updated - - -

I'd agree with RRR..Make sure she's level. Bigger deal than one may think. Use a one man bleeder or a chunk of aquarium hose into a soda bottle and pump those brakes. Not a fan of gravity bleeding at all. Pesky air up by the master or stuck by the prop/distribution valve can be a pain as well. I'll take the master cylinder over off and very very slowly press down on the brake and very very slowly let off the brake (too fast brake fluid will splash out into your engine bay) and watch for bubble's coming up through the brake fluid in the master. Usually always see some if a line has been changed out or removed. Plus it's another way for you to tell if your piston seals are junk in the master if it keeps on bubbling up in the reservoir, and you don't have leaks anywhere else.

Good luck.

Prop wash, Thanks for the info. I did this with my MC cover off. Are you saying that the fluid should not break the surface of it in the MC whether it be air bubbles or all fluid? This is on the upstroke of the pedal when I get mine.

 

[Propwash]

No problem. Fluid coming up is just fine cornpatch....Depending how fast you push the peddle down or let up, you may have the fluid percolating up in the master cylinder a bit. You'll at least see the brake fluid stir a little bit while pumping the peddle. Like I said, don't pump too fast and have it spout up or spill over. Brake fluid likes to eat paint. Don't let the fluid get low either. Don't want to suck air right into your lines. If you have air bubbles coming up, keep cycling the pedal till you don't. If they don't go away after a couple minutes, fluid is leaking out somewhere and air is getting in. Hope it helps.

 

[Cornpatch MO]

I got my spongy brake pedal fixed today. ( disc-drum) It was all in the drum circuit. First adjust the brake shoes all the way out till they lock up. I had someone to pump the brake pedal and refill the MC when needed. I put a piece of aquarium tubeing on the bleeder furtherest from the MC and ran it to a clear jar with a little brake fluid in it. submerse the end of the tube into the fluid. Push the pedal down, open the bleeder, air bubbles come up in the fluid in the jar. Close bleeder, release the pedal to come back up. Repeat until there are no more bubbles and then move to the next wheel brake cylinder. Do the same thing on it. After I got some more brake fluid in the jar, I put it back into the MC as everything was new and clean.

Disc brakes were a snap as the bleeder is in the very top of the caliper.

I don't care what anyone says, I use silicone Dot 5 brake fluid on a brake system that does not have ABS anti- lock brakes. That is- if all new lines, MC, and brake cylinders are replaced. DO NOT MIX IT WIT DOT 3 OR 4. I have used Silicone brake fluid for 7 years on my 56 Chrysler, No Problems. The thing I like about silicone BF is- it does not damage paint, keeps your MC clean ( no rusty scum) and does not absorb moisture = no rusty looking brake fluid. ............................MO

 

[Propwash]

Glad to hear you got your brakes squared away Cornpatch.