Brakes

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manyo

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Hello all,

I have a little brake issue( I hope). When I fire car up, brake light on dash lights up and brake pedal is in an upward position and difficult to depress. All the brake lines were just replaced and fluid is at a good level. Any suggestions??

Thank you in advance.

 

japrine

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Hello all,

I have a little brake issue( I hope). When I fire car up, brake light on dash lights up and brake pedal is in an upward position and difficult to depress. All the brake lines were just replaced and fluid is at a good level. Any suggestions??

Thank you in advance.
Does your car have a power brake booster? maybe the vacuum line?

 

72HCODE

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does the light go out after and the pedal return to normal operation?

if the light stays on it indicates a imbalance in the system one side is leaking or has air in it, so there is a pressure difference.

it could mean a problem with the prop valve or master as well.

the pedal being hard to press could be a problem with the master, booster, pushrod, or pedal under the dash.

 

Bill73Ragtop

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former owner (25 yrs) of 1973 Convertible, 351c, A/C, RA
What type of brake fluid did you install? Dot 5 is a no-no these days. Dot 3/4 is the way to go.

Booster Test: Vacuum Brake Booster Testing and Diagnosis

Minimum engine vacuum required is 18”HG at idle in gear.

You will need a vacuum pump with a gauge to perform this procedure. Most “chain” parts stores will rent, loan or sell them.

1) Remove vacuum hose from check valve on booster. Place hose from vacuum pump onto check valve and draw booster to 20”Hg of vacuum.

2) Let booster sit with vacuum applied for 5 minutes. Vacuum should remain steady at 20”Hg. If vacuum does not stay steady at 20”Hg the booster it is faulty and will need to be replaced. If vacuum does hold steady at 20”Hg proceed to step 3.

3) With 20”Hg of vacuum in booster depress brake pedal once and release it. The booster should transfer SOME but not ALL of the vacuum. Depending on how hard the pedal is depressed it is normal to see a 5-10”Hg drop in vacuum. The most important thing is to ensure that the booster does transfer SOME vacuum but does NOT transfer all of the vacuum in its reserve. If vacuum remains at 20”Hg OR goes to zero the booster is faulty and will need to be replaced. If vacuum transfer is within the above range proceed to step 4.

4) Once again draw booster down to 20”Hg of vacuum. Depress brake pedal and hold down for 30 seconds. You should see the vacuum gauge drop slightly and then hold steady. Vacuum should stay steady as long as you are holding the pedal down. If vacuum drops while pedal is being held down the booster is faulty and will need to be replaced.

 

manyo

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Hello all,

I have a little brake issue( I hope). When I fire car up, brake light on dash lights up and brake pedal is in an upward position and difficult to depress. All the brake lines were just replaced and fluid is at a good level. Any suggestions??

Thank you in advance.
Does your car have a power brake booster? maybe the vacuum line?
yes it does have power brakes. Vacuum line and fitting on end is new.

thanks


Thank you all for the suggestions. I did not bench bleed master cylinder after it was removed during restoration. I will start there.

thanks again guys!!

 
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manyo

Well-known member
Joined
Oct 21, 2013
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Location
Washinton Twp, MI USA
My Car
71 Mach 1
Hello all,

I have a little brake issue( I hope). When I fire car up, brake light on dash lights up and brake pedal is in an upward position and difficult to depress. All the brake lines were just replaced and fluid is at a good level. Any suggestions??

Thank you in advance.
Does your car have a power brake booster? maybe the vacuum line?
Hello All,

Problem solved. After thinking I needed to replace booster I thought for the heck of it I would put the old hose and valve combo back on the car. Suddenly my brake light went off and the brake pedal movement was restored. I guess the hose I used was incorrect . I did check it and it did not appear to have any kinks or any signs of collapsing but for some reason just did not work.

Anyhow thanks to everybody for the help!!

 
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