The Stovebolt Site Forums The Shop Area The HiPo Shop %#$% Soft Pedal HELP!!!!!!

Installed CPP front disc brakes with booster on my "54" 3100 everything is located in the original location on the frame. I bench bled the master cylinder and than bled all the brakes but could not get a hard pedal. I than removed the master cylinder and bench bled it a second time just in case and I installed residual check valves on the porprtioning valve in case I was getting any bleed back, I than bled the brakes again still a soft pedal, if I pump the pedal a couple of times it gets firm. I am at a loss as what to try next any ideas are welcome. Could the master cylinder be bad, bad proportioning valve how do I know if I have a faulty part or just operator error???
Thanks
Mike

Hy mperk, are you sure your proportioning valve is still centered, and hasn't shuttled over to shut off one system or the other? Some valves have special tools to hold the valve in the centered position while you bleed the system. Do you have the warning light hooked up? If you don't you might check the terminal and see if it is grounded, hope that helps.

Did the master cylinder come with the disc brake calipers ?
There might not be enough fluid volume for the master piston to stroke the system.
If its a new dual master do you have the lines connected to the correct ports, front to back ?
You don't say if the back brakes are new as well ?
Manually adjust them right out to the drums before bleeding them again.

Also check the plunger rod which goes from the pedal into the master cylinder and be sure it is set at the correct length so it activates the master cylinder as soon as you depress the brake pedal.

Are the rear brakes set too loose? To much travel for the pads to make contact can give that symptom.

Would be worth checking the adjustment on the brake booster's pushrod if you haven't already done this.

Where the booster's pushrod goes into the master cylinder, there should be a just small amount of clearance, usually aboout .025"-.030". Much more and you'll lose useful pedal movement; no clearance often causes the brakes to lock up when they get hot.

Check all those things the guys have mentioned & if you still don't have a good pedal you still have air in the system. I had the same when I got first got my 58. It had a disc/drum conversion. The lines have a lot of up & down & curves & it took more bleeding to get it all out. Now it has a real good pedal & fantastic brakes.

Just a question. Did you switch to DOT 5? It can be harder to bleed sometimes.

Stupid question here. Do you get the same result with the engine running? The brakes will feel inadequate without the vacuum assist from the running engine.

The pedal seems to be the same whether the motor is running or not, the first push of the pedal will go all the way to the floor if I pump it one more time I have a alright pedal, one more push and the pedal is pretty stiff. I am thinking about just leaving the transmission cover off and just using the ole Flintstone method, gots to get some steel toe boots lol!!!!

I'd start with rear brake shoe adjustment. If that doesn't help, bleed the rear and then front again.

are you getting air or fluid movement at all 4 wheels during the bleeding procedure. is the pressure coming out about equal to one another. are you mechanically bleeding or by someone doing the foot work
ron

after a bleeding session do you get full pedal pressure and then change or it doesn't change at all during the bleeding session. when you start the bleeding again are you getting air and is it more predominate at 1 wheel more than the others

We are bleeding by someoneone doing the footwork, the first time we bled them I got some air bubbles coming out but after pumping and bleeding a couple of times we would no longer get air. It seemed that at times we had a pretty good pedal but once the job was complete it would not be firm any longer, really getting frustrating now, just not sure what to try next. If I knew someone that was experienced in brake work I would take it to them but it seems now adays if they can't put it on a computer or have to think the machanics are lost!

Are the bleeders on the front calipers at the top of the caliper? If at the bottom of the caliper, swap calipers from side to side.

John

They are on the top, when we started bleeding I started at the furthest bleeder in the rear from the master cylinder and then worked my way to the front to the closest one I have read that different people do it different ways as far as shortest to furthest.

Are the rear pads adjusted close to the brake drum?

you are getting air somewhere. check all fittings for being tight and that there are no kinks in your lines where it could have crack especially if you had tried to straighten it out.
sometimes the most difficult part is for people to understand when bleeding brakes is the person who is doing the pumping. when you tell them to stop and hold it down, that they are not to lift the pressure off until you tell them to every SOB'in time or you will get air. this can easily happen with kids or wives who get impatient or don't really give a poop
sometimes as previously stated it takes a lot of bleeding.
left rear-right rear(passenger side), right frt and then to left frt.if the lines are set out basically in the stk position(rear)
ron

Let us know what you find.

When bench bleeding the master cyclinder does it matter if the plastic tube used to circulate the fluid back to the master cyclinder is submeged in the fluid or should it be out of the fluid or does it matter. It seemed when it was out of the fluid I was getting alot of bubbles but once I submerged it they went away???
Thanks
Mike

That is a very good question and I do not know the correct answer.

I can speculate that when submerged the fluid, bubbles and all, would be moved back and forth through the tube and you might not get them all the way through the tube thus leaving them in the system. My best guess would be that you need to use as short a tube as possible.

The tube absolutely needs to be kepts submerged, keep pumping it around until all the air is gone, and then do it some more.
And then be careful; not to tip it or push the plunger until its all installed.
Then don't let it get low at all, keep topping it up after every pedal push.
Good luck!

I had this exact same problem on my 49 Sub. I adjusted the rear shoes up tighter to no avail. I bled and re bled. I was ready to live with the problem because after one pump I had good brakes. I then took it to a local garage for an oil change that still has a couple of gearhead mechanics. While up on the lift the one gearhead asks me "do you know you have the lines connected to the master cylinder wrong?" No I replied, does it make a difference? Yes, he says, front brake lines go to the front port of the master cylinder and rear brake lines go to the rear port of the master cylinder. I had him change them around and problem solved.

Weeds

I had much the same issue. In my case, it was the rear adjusters. Once I got them dialed in, my brakes were fine.