Low, Touchy Brake Pedal

Rutty

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Hi All,

I've been going though the brakes on my '68 Newport and finally have them working to the point that I can drive it. I've replaced all the cylinders including the master along with the brake lines. I haven't replaced the drums, shoes (including hardware), and brake booster.
The problem I'm having now though is that the pedal travels almost to the floor before it engages the brakes and once it does it's really touchy (maybe 1" travel from where it starts to engage to total engagement). I have adjusted the brakes by driving in reverse and hitting the brakes five or so times. I cleaned up the self adjusters when I went though the brakes so believe they all should have adjusted. I can tell that they're engaging much better but the pedal is still really touchy and low when applied.
This is my first C body so I don't know if this is normal brake behavior or not. It doesn't seem right to me. BTW this car has drums all around.

Thanks,
Matt
 
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Davea Lux

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Hi All,

I've been going though the brakes on my '68 Newport and finally have them working to the point that I can drive it. I've replaced all the cylinders including the master along with the brake lines. I haven't replaced the drums, shoes (including hardware), and brake booster.
The problem I'm having now though is that the pedal travels almost to the floor before it engages the brakes and once it does it's really touchy (maybe 1" travel from where it starts to engage to total engagement). I have adjusted the brakes by driving in reverse and hitting the brakes five or so times. I cleaned up the self adjusters when I went though the brakes so believe they all should have adjusted. I can tell that they're engaging much better but the pedal is still really touchy and low when applied.
This is my first C body so I don't know if this is normal brake behavior or not. It doesn't seem right to me.

Thanks,
Matt

It sounds like your travel rod is improperly adjusted. Before changing the settings on the travel rod, be sure the brakes are properly adjusted on all 4 wheels if equipped with drum brakes. The travel rod usually needs to be reset every time a master cylinder is replaced. Remove the master cylinder from the brake booster. You will note that there is a threaded adjustment nut on the end of the rod. The FSM gives detailed instructions on how to adjust the travel rod. You can download a copy for free at www.mymopar.com. Manuals are in the tools/reference section from the home page. As a starting point, turn the adjusting nut out about 1 1/2 turns and reinstall the master cylinder. Note where the pedal starts to engage the master cylinder, you should have about 5/8" free play, so continue to adjust until you have that number.

Dave
 

Ross Wooldridge

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Without disconnecting the lines, remove the nuts holding the master on the studs and slide the master away from the booster (or the firewall if it's manual brakes) and ensure that the brake pedal pushrod is adjusted properly.

With a power brake car, the pushrod coming out of the booster should have a knurled part that will extend or retract to adjust the length - the rod should hold the master away from the booster 1/16th of an inch before you bolt it down. I assume the same is for a manual brake system, but I don't know for sure. Check the FSM.
 

Rutty

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Thanks for the advice guys! I'll have some time tomorrow to check to make sure the brakes are adjusted properly at all four wheels. Then I'll check the rod. Sounds like that's the culprit. I'll report back what I find.
 

Big_John

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Before you do anything... One quick test.

With the engine off. Pump the brake pedal until there's no "assist" left. Now push on the pedal... Does it stay high and hard? Or does it sink to the floor? Does it get better if you pump it a couple times?

A well functioning, correctly adjusted brake system will have a high, hard brake pedal with the engine off. If it's spongy, you have air in the line. If it's low and hard, and goes to the same place, it's probably an adjustment in the brakes themselves or possibly the push rod.

Depending on the self adjusters to take up the slack might not be working too... Assuming they are assembled correctly, I'd still take up the slack manually to be sure.

The brake pedal in these cars tends to feel a little "touchy" to those who aren't used to them. Shouldn't be a low pedal though.
 

CBODY67

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The self-adjusters were not meant to do all of the adjustment of the brakes, just maintain the adjustment that was already there. Which means that for them to work as they are designed, you have to have the basic adjustment correct FIRST. I suspect that when THAT is correct, the "pedal" will be "high and hard" as @Big_John noted.

As @Big_John mentioned, if you are new to '60s power brakes, then they will seem touchy compared to a modern power disc brake car. One of the luxuries of the "upper level" cars from back then was the effort you did not have to use to operate them. That means power steering and power brakes. Light touches were all that was needed, which is what the market demanded back then. In many cases, the effort it took to operate the throttle and what happened when you did was also in that mix.

Just some thoughts,
CBODY67
 

live4theking

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How about a picture of your master cylinder. Long before I bought my 68 NYer someone replaced the master. Unfortunately they replaced it with one for disc brakes. This made them extremely touchy. The quick tell is that the drum brake cars the cover is held on with a bolt, disc brake master are held on with a bail.

Drum brakes
131323-rit__ra_p.jpg

Disc Brakes
CE_13063047_Ang__ra_p.jpg
 

CBODY67

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Drum brake cylinders, sometimes, are held on with a bail, too. BUT the disc brake cylinders usually have an unevenly divided reservoir (the front discs take a larger volume of fluid to work) whereas the drum brake cylinder reservoirs are evenly divided.

Enjoy!
CBODY67
 

Rutty

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Ok, so I feel a little stupid right now.
Today I did some of the things you guys suggested. I jacked up the front wheels to check the brake adjustment. Both front brakes were dragging slightly off and on so I didn't bother adjusting them. They still didn't engage until the pedal was almost to the floor.
Next I checked the pushrod in the brake booster which I adjusted out till there was about 1/16" (preload) in it. This didn't change the pedal height.
Finally after one of the last posts about the master cylinders being different between drum and disc brake cars I decided to take a picture to post so someone could verify I have the correct one and this is what I found.
20210806_203643.jpg
 

Rutty

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The front brake fluid reservoir is essential empty. I'm guessing this is my problem. Either the shop I brought it to to bleed the system bled it empty or I have a leak somewhere. The weird thing is the front brakes are still working even with the empty reservoir. The pedal doesn't build up pressure with pumping so it doesn't seem like there's air in the system. There must be though. I'll have to rebleed them now.
 

CBODY67

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Try just adding fluid. Fill the reservoirs with fluid, but not quite to the top. Pump the brakes lightly and quickly, short quick strokes to put small pressure spikes into the system, somewhat mimicing what an ABS brake system does when it works, just not to the same degree. What this does is to pressurize/de-pressurize the fluid so that any bubbles will come to the top. Then let things sit for a while. Recheck pedal travel issues. Check for brake fluid leaks at brake line joints, the three flex hoses (2-frt, 1-rr), and the 4 whl cyls). Hopefully, your pushrod adj did not disrupt anything.

As for the pushrod adjustment . . . I suspect that anybody who might replace a master cyl will not mess with that adjustment, just replace the master cyl and nothing more. I also suspect that even fewer people know there is a way to measure the adjustment if it's not right, or to just check it. But, at this point in time on vintage vehicles that the service history is not known, consult the FSM for the correct length/adjustment for most optimum outcomes.

Just some thoughts,
CBODY67
 

Ghostultramarine

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This thread answers some of the questions I was going to post.

BUT I was looking at Rock Auto and there are a few different makes for the master cylinder (if one was to replace it). Which are better? (It doesn't have to be a Baer or Wilwood (they don't sell them there).)
 

Ghostultramarine

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@Rutty , if you do not have the Factory Service Manual (FSM) for your 68, it is NOT available on mymopar, as far as I could tell, I do have a paper copy and I could photograph the pages regarding the brakes for you.

Just let me know.
 

furious70

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You've obviously got an issue there but even when working I'd describe the oem system as a pretty low pedal and touchy
 

Ghostultramarine

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6D40BD25-6B72-4EDE-821F-2BBF42F4D7C8.jpeg
18A9FFE9-6759-4155-A8B1-2EC762950FC1.jpeg
3F321999-B2AE-4574-ABE3-54353AD95CA3.jpeg
Final ones.

Not sure if you have drum or disc brakes so I included both; figured someone may find the other useful.

(I did not take the pictures on their side, not sure what happened when uploading.)
 

Ghostultramarine

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I could not find a part in the manual that shows the brake pedal, itself, and how it is attached, adjusted and assembled. There is a section like that on the emergency brake.

Page 5-11 has testing procedure and 5-28 service diagnosis.
 
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