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Old 08-30-2020, 09:43 PM   #1
Phil Gillespie
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Default Hydraulic Brakes 39 Ford.

39 Ford Coupe Hydraulic Brakes .
The master cylinder to my knowledge has not been serviced/rebuilt.
MC is not leaking oil or overfilled.

Recently fitted a set of auto bleeders all round. Just the other day brake pedal came up really tight and brake lights came on. Also noted brakes were "on" without any foot on pedal. Released some oil out a rear bleeder and came right.
Brake light came on a day or so later sitting in garage.
Went round all brakes, bled them all and now brakes still work but needs about 1/2 pedal to engage. Previous approx 1/4 pedal travel for brake engagement.
My thinking is time for MC replace rebuild. Pedal travel has not been adjusted.
Thoughts, suggestions?
Phil NZ
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Old 08-30-2020, 09:50 PM   #2
19Fordy
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Default Re: Hydraulic Brakes 39 Ford.

First, try to adjust the pedal travel.
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Old 08-30-2020, 10:18 PM   #3
Phil Gillespie
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Default Re: Hydraulic Brakes 39 Ford.

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Originally Posted by 19Fordy View Post
First, try to adjust the pedal travel.
I did not want to adjust pedal travel as previously the pedal came up tight and brakes on. The reason for this? Fault in M/C? Normally pumping pedal gets brakes up tight at pedal but not this time.
Phil NZ
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Old 08-30-2020, 10:37 PM   #4
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Default Re: Hydraulic Brakes 39 Ford.

You have to have free travel at your brake pedal for the master cylinder to work properly, to let he pressure out of the system. the brake pedal should move 3/4" before the push rod moves the master cylinder piston. I your brakes still come on after you have the free travel you have a master cyl problem.
Phil.
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Old 08-30-2020, 10:51 PM   #5
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Default Re: Hydraulic Brakes 39 Ford.

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Originally Posted by Ideucev8 View Post
You have to have free travel at your brake pedal for the master cylinder to work properly, to let he pressure out of the system. the brake pedal should move 3/4" before the push rod moves the master cylinder piston. I your brakes still come on after you have the free travel you have a master cyl problem.
Phil.
Thats what I'm thinking hence inquiry now on price of M/C & a M/C rebuild kit as this is an item not touched to date by myself.
Phil NZ
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Old 08-31-2020, 06:16 AM   #6
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Default Re: Hydraulic Brakes 39 Ford.

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Are you sure that the pedal return spring is still pulling the pedal ALL the way back up? DD
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Old 08-31-2020, 07:29 AM   #7
Phil Gillespie
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Default Re: Hydraulic Brakes 39 Ford.

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.

Are you sure that the pedal return spring is still pulling the pedal ALL the way back up? DD
For sure as it returns all the way same height as clutch pedal.
Phil NZ.
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Old 08-31-2020, 08:11 AM   #8
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Default Re: Hydraulic Brakes 39 Ford.

So, Phil, the only thing you did before this lock up started was to replace the bleeder screws with speed bleeders?
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Old 08-31-2020, 08:13 AM   #9
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Default Re: Hydraulic Brakes 39 Ford.

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So, Phil, the only thing you did before this lock up started was to replace the bleeder screws with speed bleeders?
Yes thats correct. And topping up brake fluid of course.
Phil NZ
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Old 08-31-2020, 08:37 AM   #10
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Default Re: Hydraulic Brakes 39 Ford.

You should have the vented cap on the MC. Are you sure the vent is clear?
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Old 08-31-2020, 09:07 AM   #11
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Default Re: Hydraulic Brakes 39 Ford.

This may sound silly but , is it possible to have created an air lock in the MC or somewhere in the system? We are all assuming that you used the correct bleeding procedure. I have bled the brakes on my 40 many times using Speed Bleeders with no problems. Hope you solve the problem.
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Old 08-31-2020, 09:12 AM   #12
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Default Re: Hydraulic Brakes 39 Ford.

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This may sound silly but , is it possible to have created an air lock in the MC or somewhere in the system? We are all assuming that you used the correct bleeding procedure. I have bled the brakes on my 40 many times using Speed Bleeders with no problems. Hope you solve the problem.
Also, might one of your speed bleeders be faulty? It has happened to me...the check valve isn't "checking" properly??
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Old 08-31-2020, 09:16 AM   #13
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Default Re: Hydraulic Brakes 39 Ford.

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Originally Posted by RKS.PA View Post
Also, might one of your speed bleeders be faulty? It has happened to me...the check valve isn't "checking" properly??
Valid point re-check valve not checking. As instructions are to release only 1/2 turn for speed bleeders.
Phil NZ
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Old 08-31-2020, 10:03 AM   #14
Phil Gillespie
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Default Re: Hydraulic Brakes 39 Ford.

Thinking now I may need to recheck my use of the speed bleeders and only go with 1/4 turn open may have been a little heavy handed at 1/2 .
This is the easiest to check later on today.
Appreciate all the helpful and thought provoking comments
Phil NZ
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Old 08-31-2020, 10:42 AM   #15
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Default Re: Hydraulic Brakes 39 Ford.

I would think the only way the Speed-Bleeders could fail would be to leak, which should be obvious if that's what's happening. If they're not leaking, I can see no way they could add more pressure or fluid volume to the system.

Being an avid fan of Speed-Bleeders. I look forward to what you find.
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Old 08-31-2020, 11:13 AM   #16
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Default Re: Hydraulic Brakes 39 Ford.

Brakes staying on can only be caused by the recuperation port being blocked. either blocked by some debris or blocked by the piston seal not being clear of it at rest. The pedal may be level with the clutch, but does it come up further if you physically lift it?
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Old 08-31-2020, 11:18 AM   #17
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Default Re: Hydraulic Brakes 39 Ford.

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Originally Posted by tubman View Post
I would think the only way the Speed-Bleeders could fail would be to leak, which should be obvious if that's what's happening. If they're not leaking, I can see no way they could add more pressure or fluid volume to the system.

Being an avid fan of Speed-Bleeders. I look forward to what you find.
Denny, agree about the leaking. And I, too, am a big fan...have them on all my cars. However, if the check valve fails to "check" couldn't that let air seep back into the system? I wouldn't necessarily see it because I'm in the car pumping the brake pedal?
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Old 08-31-2020, 11:40 AM   #18
Phil Gillespie
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Default Re: Hydraulic Brakes 39 Ford.

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Originally Posted by Mart View Post
Brakes staying on can only be caused by the recuperation port being blocked. either blocked by some debris or blocked by the piston seal not being clear of it at rest. The pedal may be level with the clutch, but does it come up further if you physically lift it?
Mart as you correctly point out the cause of brakes staying on as you state.
Pedal returns to floorboard underside and will contact here. This has been the norm for me. Will as above recheck again.
Phil NZ
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Old 08-31-2020, 12:21 PM   #19
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Default Re: Hydraulic Brakes 39 Ford.

Piston in MC may not be returning all the way possibly created by rust or debris.
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Old 08-31-2020, 12:36 PM   #20
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Default Re: Hydraulic Brakes 39 Ford.

How about the length of the rod that goes into the cylinder from the brake pedal??
Paul in CT
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