Bleeding Brakes

[Ranger]

Replaced all 4 wheel cylinders (manual drum brakes). Bled them 3 times today and the damned thing still has air in the lines. :brickwall: Frustration level is very high!

P.S.
Probably common knowledge, but the front bleeders are a royal PITA!

 

[mahoney0_00_3]

power bleed them!if they are all new gravity bleed them!

 

[Ranger]

Bled them again this morning. Nothing but fluid from each one, yet the pedal goes "almost" to the floor, is soft and can be pumped up. There is air in there somewhere, but I'll be damned if I can get it out. I even cracked both line fittings at the MC and got no air out of them either. I'm at wits end!

 

[Big John]

I was afraid to say this... but has the master cylinder been in the car for long?

Here's what I have had happen to me... several times as a matter of fact.

The master cylinder will work great until you bleed the brakes. The bore of the cylinder is nice and smooth where the piston cups rub, but outside that range, it's kind of fugly. There may be a build up of sludge complicated with a ridge worn in the bore. Then you get in there with your size 12's on the brake pedal that goes all the way to the floor. The piston cups catch the ridge and that's all she wrote.

So, it's very possible that you may have a bad master cylinder. You will be able to pump the pressure up, but the pedal will still sink to the floor.

If it's not that... let's go with my favorite method for bleeding brakes and try that.

Starting with the farthest one and working your way to the closest.

Put an assistant in the car. My first wife actually got good at this. My second wife... not so much, but she looks better sitting there.

Have them pump the brakes three times. On the third stroke down, they hold the pedal down and yell "down" or I guess you can use some other catchy phrase.

Important--- They hold the pedal down until you tell them to release.

Crack the bleeder. I suggest putting a small rubber hose into a bottle to keep the brake fluid spray to a minimum. A clear bottle with brake fluid in it works great because you can see if there are air bubbles in the fluid.

Tighten the bleeder and tell your assistant to release the pedal. Rinse and repeat for the other three wheels.

The alternative method if you are by yourself is to use a hand vacuum pump with a bottle in the line.

Again... farthest to closest...

Connect the pump and get a little vacuum started. Again, crack the bleeder and watch the stream.

Hope this helps...

 

[Ranger]

That's the old tried & true method I have been using to bleed them John.

As for the MC, my buddy said the same thing, bad MC because it is probably 45 years old, but here's the catch. You can pump them up and they hold. The pedal does not slowly sink (until I open the bleeder valve). That's why I ruled out a bad MC. I've never seen anything like this before. For a lack of anything else to do, I think I'm just gonna go back and keep pumping brake fluid through the system til that damned pedal hardens up (hopefully).

 

[rockdog2112]

F**k! I know. I hate them.

 

[rockdog2112]

I agree about the MC. Had the same issue a few months ago. I replaced it(major pain in the ass) and life was good again.

 

[droptop]

Sounds like air in mc to me.

 

[Big John]

If the master is that old, maybe you need to replace it anyway.

 

[Ranger]

Really? Even if it doesn't leak down?

 

[Ranger]

Hmm, found something interesting while searching for MC.

This is a Cardone MC for a '69 RR WITH PB (and looks just like the one on my (manual brake) car. Note the cover hold down.


This one is listed by Cardone as for manual brakes. (The manual brake Dorman looks like this one as well)


Is it possible someone installed the wrong one on my car?

EDIT:
When all else fails, consult the FSM. It pictures the upper one used on the manual brake AND the power brakes. :huh:

 

[Big John]

Stuff wears out. You put yourself and your family in it, you need to be sure it stops.

 

[Big John]

The upper one is correct.

Here's a tip... when (if) you turn in the old master cylinder for a core, keep the cover. IIRC, they interchange.

 

[Ranger]

Yeah, I suppose even without symptoms of a bad MC I probably should change it for $30. I can probably even swap the covers for originality. I'll order a new Cardone.

EDIT:
Oops, I see you already added the cover swap. Good to know. Thanks.

 

[Ranger]

In the process of changing the MC now and it is fighting me all the way. I finally got the 4 mounting bolts off from under the dash (royal PITA). MC would not release from the brake push rod. Thought I needed to remove the 2 bolts and flange on the back of the MC, wrong. That just released the piston from the MC, not a big deal. So now I have the piston assembly attached to the push rod. It will spin and I can hear rubber squeaking as I spin it, but it WILL NOT release from the brake push rod. What am I missing?

UPDATE:
Since that was getting me no where, I reattached the MC to the piston, but like two dogs in heat, the MC is still attached to the brake pedal push rod and no amount of twisting or pulling seems to help.

 

[Big John]

The piston just pulls off, but it can be hard to do sometimes.

Squeeze the aluminum piston with a pair of vice grips until it breaks apart. You're not going to need it anyway.

 

[Ranger]

Alright, I'll give it another shot tomorrow and be a a little more "persuasive", but my fear is that I may clamp that piston tighter to the push rod rather than break it apart.

Thanks for the replay. Will update tomorrow.

 

[Ranger]

One more question that the FSM seems rather vague on. I assume that the piston retainer is just for shipping, and removed for installation and the flange then becomes the retainer? It seems as though it has to be, because the retainer screw is in the lower flange bolt hole.

EDIT:
My assumption was correct.

 

[Ranger]

Success! I finally dribbled a bit of oil on the push rod and let it work it's way down to the rubber ring on the end of the rod. That was enough to finally let it slip out. Without that, it was not coming out.

I was able to swap the original cover. Just had to drill out the hole in the clamp and cover and use a shorter bolt than the one that came with it (the original bolt was a different thread).

So, new front shoes, wheel cylinders & MC.

Now I just have to figure out where the air is and get the pedal up. Then it's on to the steering gear box. I'm sure that will fight me as well.

 

[69/b5/n96]

sounds as thou you need to bench bleed the master or replace have hade the same battel!!