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1969 Mustang convt
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Discussion Starter #1
Hello from sunny and beautiful lock down Italy!

I bench bled & reinstalled the cleaned and refurbished 1" bore m/c and bled the brakes and took my 69 Convt for a drive.......and so far no leaks :)

In a "panic stop" situation the car does NOT stop quickly enough though. I cannot lock the front brakes no matter how hard I push on the pedal.
The brakes feel s bit spongy.....it doesn't have that solid feeling of "I'm stopping NOW!"..... I slam on the brakes and the car says "......I'll stop in a few seconds".

M/C is good, booster is also good, rotors and pads are fairly new (500 miles).

I have a Granada conversion kit installed with 1 piston calipers in the front and drums in the rear. The proportioning valve is turned counterclockwise all the way (to give the front 100% hydraulic pressure) .... I cannot lock the front wheels for the life of me!

Tomorrow I'll check that the rear have a little drag when spun by hand, I'll also make the booster push rod a smudge longer.

Stay safe & thanks for any suggestions or input......... and remember please stay home..... it's still a crapshow here in Italy.
 

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The proportioning valve should have no effect on the front brakes. It limits pressure to the rear. If the pedal is spongy bleed again.
 

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Hello from sunny and beautiful lock down Italy!

I bench bled & reinstalled the cleaned and refurbished 1" bore m/c and bled the brakes and took my 69 Convt for a drive.......and so far no leaks :)

In a "panic stop" situation the car does NOT stop quickly enough though. I cannot lock the front brakes no matter how hard I push on the pedal.
The brakes feel s bit spongy.....it doesn't have that solid feeling of "I'm stopping NOW!"..... I slam on the brakes and the car says "......I'll stop in a few seconds".

M/C is good, booster is also good, rotors and pads are fairly new (500 miles).

I have a Granada conversion kit installed with 1 piston calipers in the front and drums in the rear. The proportioning valve is turned counterclockwise all the way (to give the front 100% hydraulic pressure) .... I cannot lock the front wheels for the life of me!

Tomorrow I'll check that the rear have a little drag when spun by hand, I'll also make the booster push rod a smudge longer.

Stay safe & thanks for any suggestions or input......... and remember please stay home..... it's still a crapshow here in Italy.
By adjusting the proportioning valve all the way you have only reduced the rear brake pressure not increased the front. The proportioning valve is only for the rear brakes. You need to adjust the proportioning valve to allow the rear brakes to work properly.
 

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Are your front pads the cheap organic, middle of the road semi-metallic or top of the line ceramic?
 

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Also, how are the brake hoses? After a while, they deteriorate from the inside, swell under pressure instead of applying all the pressure to the piston / wheel cylinder. New hoses, especially braided hoses, help. You can paint them black for camo.
 

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1969 Mustang convt
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Discussion Starter #8
Hey everyone,
I re-bled the brakes today. the calipers are on correctly with bleeder facing the rear.....and still could not lock up either front or rear by standing on the brake pedal with BOTH feet from about 60mph.
Tomorrow I'll check how much vacuum I'm getting to the booster and I'll make the booster push rod a bit longer (again).
....don't know if this maters but I can't get the brake pedal to the floor. it has a short and hard travel.
I could buy new flex hoses but I live in Italy and I gotta wait till my next trip to the US to see my kids......no time soon thanks to Covid 19.
I believe I have the Raybestos RRD14 riveted pads on them now (see picture).
748942
 

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Some people do ... some people don't, did you bleed the M/C before plumbing it in?
Edit: just saw that you did. :oops:
 

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Discussion Starter #14
I just emailed SSBC with the broken pin and the fact that there's no change in the braking with various rod lengths. I'll let you know what they say as soon as they answer me.
 

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It might be time to look at your calipers. When they sit, moisture in the brake fluid tends to find the lowest point and they rust and stick. THis is especially a problem on new aftermarket units from China, I'm not sure what type of Cromesque alloy they use but I just had a set rust and stick within in a year of replacement on my DD Volvo. The tendency is that they stick on and will heat up the hub to the point that it will be painful to touch the center of the wheel. If you are sure your master is known good, then I would pull the calipers and and use a C clamp to press the piston home. Make sure it moves easily and smoothly. Also, on the one piston systems, its critical that the caliper slide easily on the pins to equalize the pressure on both sides of the disk. Make sure the pins are clean and the calipers slide freely...

One last thought, I'm not sure about a '69, but is there a chance that it has a differential switch in the system with a brake warning light. Usually a brass fixture where both the front and rear tubes from the master connect. There is usually a electrical connection between the two lines from the master that goes to a dash lite. If so, did you ever have a problem in the front circuit or push the brakes with a caliper off on the front circuit while the rear was connected. Usually systems like this have a brake light in the interior that comes on when the shuttle is off-axis indicating a problem with the brakes. If the bulb was burned out or the circuit interrupted, and the shuttle "thought" there was a problem in the front circuit it would shut down the curcuit. I do not know how to reset one or even if its possible, I'll let others chime in on this...

Is this a new system that never worked correctly or is this a new problem on a system that worked well at one time?
 

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You may have said earlier, but what mods have you done to the engine and will your cam profile create enough vacuum for power accessories?
 

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Discussion Starter #17
I havent changed anything in the engine. I've replaced and changed gaskets, water oump, oil pump ecc eccbut everythi g is original. The vacuum i get from the hoses to the power booster is 17,5 to 18. So i know i'm good with that.

The brake warning light was already removed when I purchased the car 20 years ago. So it has never been functional.

I do have original rebuily calipers. I can remove them and verify is the piston travels smoothly.
Do u put grease inside the rubber housing for the 2 caliper bolts?

I'll have to test if I get a hissing sound once I remove the booster vacuum hose after turning off the engine.

I can't explain the broken original rod and the bent one that i replaced and took for only 2 drives.

Let's assume the calipers' pistons are not moving smoothly...... when I press the brake pedal with BOTH feet at 60mph shouldn't i be able to lock the front wheels anyway?
 

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I did some research out of curiosity and CV boredom, forget the differential valve issue, apparently they do not block off the circuit when activated. My bad...

As for your question about the calipers, Who knows, it depends on how bad they are, these are long shot ideas but you have already tried the easy stuff ;o) WHile you are searching for the problem, not a bad idea to make sure everything in the system is top notch. Also, make sure while you are doing all of this you replace the brake fluid in teh system to reset your two year between brake fluid exchanges.
 

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Discussion Starter #19
All the brake fluid (bench bled mc & lines) is 1 week old :)
I'm really curious to know what SSBC is gonna say about the broken rod.
Tomorrow I'll test the brakes with and without the booster....and try to listen for the hissing sound once i remive the vacuum hose.

Thanks for all the brainstorming :)
 

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All the brake fluid (bench bled mc & lines) is 1 week old :)
I'm really curious to know what SSBC is gonna say about the broken rod.
Tomorrow I'll test the brakes with and without the booster....and try to listen for the hissing sound once i remive the vacuum hose.

Thanks for all the brainstorming :)
I thought I heard SSBC is out of business? EDIT...nevermind it helps to search first LOL

Chris
 
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