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

Tweet

Hi All!
HELP! Purchased a '48 Chevy with a power brake booster already installed. Brakes are soft. Bled them in sequence & still a soft pedal. What is next to try to get this fixed?

Thanks in advance,
Mack

How are you bleeing the system? Does it have residual valves?

Are you starting at the right rear? Then the left rear? Then the right front and lastly the left front?
Also, are you using a pressure bleeder? Or, a vacuum pump? Or are you pushing fluid backwards into the system from the wheels? Or do you have an assistant pump the pedal? If an assistant, are you pumping more than 2 "strokes" of the pedal, this may induce aeration in the fluid! Are you also keeping the reservoir full after each wheel?

So many questions.. and I'm sure others will come along and offer more ideas. Keep trying, you'll get it!

Thanks 34-40!

Yes, sequence is correct. Am using an assistant to press the brake pedal for me. He was pumping it.... many times. fluid always checked in the master cyl. Sounds like we'll try and do it with pumping.
Also, If the power booster is not working properly bleeding would still stiffen the pedal yes?

Mack

Then I would offer, DON'T pump it Many Times! Twice with the bleeder closed and don't rush! Pumping fast and often will / can cause the fluid to aerate, or trap air bubbles! Sometimes it's better to let it set overnight if you have trapped air in the fluid. Are you also using a catch can with a hose from the cylinder/caliper? This will let you see if there is air caught in the fluid when caught in a glass jar or clear plastic container.

A malfunctioning booster will make things "hard" yes.

Didn't get the air out of the master. I never do either.

Try this: press the pedal down very slow. Then release quick. Watch the master, keep doing it until you see bubbles. Then, keep it up till they stop.

how do you bleed the master? with the cover off push the pedal slowly and look for bubbles?

Another thing to consider - do you have through the frame fittings with a boxed frame? There are types of through the frame fittings that have air pockets in the middle, and getting them out can be all but impossible. You can find tech articles on them in several of the monthly's from a few years back.

Hi all!
Thanks for the input! I've found that the vacc line from the booster is not attached to anything. I have an edelbrock intake & am not seeing a port for the booster? This could be causing the brake issue or at least a contributor yes?
I bled the master & each wheel again, pedal slightly better.

Rspears, just seeing your post - will check it out! Thank You!

If you have nothing on the base of your carb to hook that big old vacuum line to, you can buy an adpter plate for under your carb that has that fitting on it. Or if you have a spot in your intake for a fitting you can just put one in there. If you do not have the place for a screw in fitting you can always drill and tap for one. The base plate is an easier solution, if you have the hood clearance.

Adjust the brakes, too much clearance in the brakes can give you a spongy pedal that seems like it needs bleeding

Thank You Bob,
I adjusted the rears and got a little more pedal! Prob need a bit more... How do I go about adjusting the fronts? Drums all around.

Its been so long since I worked on a chevvy that I don't recall exactly but I think the fronts & rears adjust the same way

Originally Posted by Mack57

Thank You Bob,
I adjusted the rears and got a little more pedal! Prob need a bit more... How do I go about adjusting the fronts? Drums all around.

Both front & rear backing plates should have the oblong rubber plug centered at the bottom, which fills the slot for the brake spoon access to the star wheel. Same process front & rear.

For drum brakes I always ran the star nutz out until the drum won't quite go on, then bank the adjuster off a couple clicks, and slide the drum on.

Then, the final step of the bleeding process, drive out o the end of the driveway, and punch it in reverse; bring the car to a stop by jabbing the brakes two or three times. This lets the self adjusters put the drums in perfect.

To answer your previous question on the master cylinder:

With the bleeder screws tight, and the cover off the master, just slowly pump the pedal, and quickly release. Any residual air will bubble out.