Brake issues

[trotti]

Ok - need some advice on brakes before I pull my hair out. I have a 100-6 that sat for some time. Safe assumption that all the components are bad so I bought and installed all new wheel cylinders, shoes, hoses. Note, this car was restored shortly before it was left to sit.

I've bled and bled the brakes and can't get a high firm pedal. I can get a high firm brake on the second pump, but it is spongy if I let the pressure off and I feel a slow pulse in the pedal when I took it around the block. I think these issues are unrelated.

I have set each adjuster on the rear till they grip the drum then back off one. Similar up front for the two adjusters on each side. Hand brake is adjusted, but is a bit easy to work (no slack in the mechanism though). The pedal will hold pressure and doesn't sink, just low.

I've manual bled, gravity bled, and used pressure bleeding. I'm using DOT 4. Ideas?

 

[Bob_Spidell]

If you press hard on the pedal, does it continue to go down, or stay firm?

Just had a SWAG: you might have some air trapped in the M/C that bleeding won't remove (many recommend bench-bleeding the M/C).

 

[trotti]

The pedal stays firm if you press hard - doesn't sink. Just isn't high.

 

[trotti]

Just had a SWAG: you might have some air trapped in the M/C that bleeding won't remove (many recommend bench-bleeding the M/C).

I did bleed in car - haven't tried bench bleeding as I haven't wanted to lift it out of the car. I might not have a choice.

 

[steveg]

Thoughts on avenues to pursue:
--tighten up all front and rear adjustments so the shoes are hard against the drums. Do not adjust until after bleeding done.
--wrap bleeder screws with teflon tape.
--use a syringe to pull the fluid out each wheel in this order: LR, RR, LF, RF
--check throw of pedal; some have had to put in adjustable clevis's and adjust them to minimize free play
--it is also possible to use a syringe to push fluid upstream from the wheels. IIRC, Mike Salter said he had a car that required that technique.

I'm using a Fiat 124 dual master cylinder which has needed bench bleeding by other installers. Avoided that completely by using the syringe to pull fluid out.

 

[Rob Glasgow]

Steve, I've not heard of using a syringe to bleed brakes. What is the technique and where do you buy this type of tool?

 

[John Turney]

.... I can get a high firm brake on the second pump, but it is spongy if I let the pressure off and I feel a slow pulse in the pedal when I took it around the block. I think these issues are unrelated.

I have set each adjuster on the rear till they grip the drum then back off one. Similar up front for the two adjusters on each side. Hand brake is adjusted, but is a bit easy to work (no slack in the mechanism though). The pedal will hold pressure and doesn't sink, just low. ...
Ideas?

Question - Do you have to do a second pump to get a high pedal if you are sitting, or just if you're moving?

Reason I ask is that if it's only when you're moving, that pulsing you feel may be out of round drums increasing the shoe to drum gap, which you then need to close up again with the first pump.

 

[steveg]

Steve, I've not heard of using a syringe to bleed brakes. What is the technique and where do you buy this type of tool?

Rob,
I keep hyping this here because the tool is cheap and works so well. Above purchase info is from Amazon.
You wrap the bleeder screws with teflon tape to keep air from being pulled in during the process. It also helps to put a tight zip tie around the clear tubing on the nipple.
Using the order, LR, RR, LF, RF, you simply pull fluid out through each bleeder screw until the bubbles no longer appear, topping up the reservoir as necessary. You'll likely have to empty the syringe around one time per wheel.

 

[trotti]

Question - Do you have to do a second pump to get a high pedal if you are sitting, or just if you're moving?

Reason I ask is that if it's only when you're moving, that pulsing you feel may be out of round drums increasing the shoe to drum gap, which you then need to close up again with the first pump.

Both - I have to pump up both while moving and while at rest.

 

[trotti]

I'm using a Fiat 124 dual master cylinder which has needed bench bleeding by other installers. Avoided that completely by using the syringe to pull fluid out.

Thanks, Steve, for the detailed response. I'll try bleeding with the shoes hard against the drums. I also noticed that the order you suggested is different from what I have been doing (right rear, left rear, right front, left front). Is there a reason for this pattern?

I'll also add teflon. I have noticed some leakage but have been getting a clear, airless push using the air-powered bleeder (EeziBleed brand) that uses pressure from a tire to push fluid out.

 

[trotti]

Rob,
I keep hyping this here because the tool is cheap and works so well.

Ordered the syringe and it should be here Wednesday. Fingers crossed!

 

[steveg]

Thanks, Steve, for the detailed response. I'll try bleeding with the shoes hard against the drums. I also noticed that the order you suggested is different from what I have been doing (right rear, left rear, right front, left front). Is there a reason for this pattern?

I'll also add teflon. I have noticed some leakage but have been getting a clear, airless push using the air-powered bleeder (EeziBleed brand) that uses pressure from a tire to push fluid out.

If you look at the diagrams on the "Brake Pipes" page in the Moss catalog, you'll see the longest distance from the master cyl is the LR pipe, followed by RR, LF and RF. This is the proper order starting farthest from the master cylinder.

 

[trotti]

If you look at the diagrams on the "Brake Pipes" page in the Moss catalog, you'll see the longest distance from the master cyl is the LR pipe, followed by RR, LF and RF. This is the proper order starting farthest from the master cylinder.

I ignorantly (and lazily?) assumed the union was beneath the master cylinder and thus the right rear was furthest - although I'd love for this to be what fixes the problem, I think I'd feel twice as stupid if this was the cause.

Thanks for the advice, Steve!

 

[austin of englan]

Your problem is adjustment, nothing to do with bleeding. Bleeding is easy, so assume you have done that correctly. Give the brakes a bit of gentle use on the road and then re-adjust.

 

[trotti]

I ignorantly (and lazily?) assumed the union was beneath the master cylinder and thus the right rear was furthest - although I'd love for this to be what fixes the problem, I think I'd feel twice as stupid if this was the cause.

Thanks for the advice, Steve!

Fresh bleed with Teflon on the bleeder screws, adjustment so tight the wheels don't move, and correct order - still a weak pedal.

It's either the need to drive and wear the shoes in and readjust as mentioned above or the master cylinder needing to be bled. Can't think of much else.

 

[Keith_M]

This is just a WAG, but none of the suggestions that you've gotten so far (which all seem reasonable to me) have worked. When you take your foot off the brake, the piston in the master cylinder has to return far enough to draw fluid from the reservoir. It it doesn't, you will have a low pedal. Maybe yours is returning far enough. Check the return spring or try pulling up on the pedal with your foot before you brake. I had something similar to this with my original master cylinder. I was never able to get it right, but a new master cylinder fixed the problem.

 

[trotti]

This is just a WAG, but none of the suggestions that you've gotten so far (which all seem reasonable to me) have worked. When you take your foot off the brake, the piston in the master cylinder has to return far enough to draw fluid from the reservoir. It it doesn't, you will have a low pedal. Maybe yours is returning far enough. Check the return spring or try pulling up on the pedal with your foot before you brake. I had something similar to this with my original master cylinder. I was never able to get it right, but a new master cylinder fixed the problem.

Gonna try this when I get home tonight. I do think the pedal is returning, but not 100% sure. If not, should be an easy fix but somehow I think I'll be bleeding the MC tomorrow and praying that works. I've got a MC bleeder kit on the way and I'm going to try the "on the car" bench bleeding process of running the outlet hose back up into the reservoir and pumping it without removal. Hoping to minimize the chance for introducing air into the system.

The good news as a result of all this bleeding is that I'm quite sure that now, after four quarts of brake fluid, my system has been THOROUGHLY flushed of contaminants!

 

[trotti]

While waiting for the master cylinder bleed kit I did a little bit of digging in the shop manual (arrived today). You are supposed to adjust the rears till they push up against the drums, but opposite for the fronts. They need to be loosened so that the return springs can suck the pistons into the wheel cylinders. Makes sense when you think of the difference between the front and rear setup.

Add this to my list of things to consider during my next brake overhaul - which, with my vast experience this go around, should take more than five minutes max.

I'll post an update after the master bleed.

 

[trotti]

No luck after bleeding the master cylinder - I'm fairly stumped. Adjusted and then bled the brakes, still have a low pedal.

 

[steveg]

No luck after bleeding the master cylinder - I'm fairly stumped. Adjusted and then bled the brakes, still have a low pedal.

It would be interesting to observe how far down the master cylinder piston travels when you apply pressure to the pedal.