Brakes on 69 are doing weird things.

[Mach ro1]

Why are my brakes lightly clamping on while driving? They only fully release about 10min after I turn the engine off. Also the rears lock up really easy.




Have front disk brakes and drum rears.
Brake pedal feel is fine.


So when at a stop in ‘drive’, if I take my foot off brake it won’t move forward naturally.... I need to give it a little accelerator to get it to move otherwise it just sits there. I can feel the brakes just lightly clamping on.

While driving, if I brake even mildly hard the rears just lock up first before the fronts do. This even happens at very low speeds of just 40kmh even.

When I turn the engine off, the brakes are still lightly clamping all round. After 10 min they seem to release.

Now, I took it to one brakes specialist yesterday for a quick diagnosis and they were a little perplexed by it. Suggested maybe the master cylinder. Even though it looked fine. Checked all fluids were good. Pads etc all great. We checked each brake and everything is operating well.

I do have a pre reservoir installed on the brake booster in the wheel well to assist brake pedal feel.


Any thoughts?
Can post pics of my set up if that helps.

Thanks

[289 vert]

Try replacing the 3 brake hoses if you don't know how old they are.

[GEOFF289]

I reckon the rod from the booster to the master needs adjustment. You'll be surprised how much difference a absolutely tiny adjustment of this will make.

[evan]

I reckon the rod from the booster to the master needs adjustment. You'll be surprised how much difference a absolutely tiny adjustment of this will make.

+1.
Might also be a faulty booster. I've had one do something similar. Check that your pedal is fully returning home.

Evan.

[Mach ro1]

Ok thanks for the replies. I’ll try these.

Could that also account for the rear drums braking much harder than the front disks and causing them to lock up so easily? It’s so odd that the braking pressure is uneven front to rear.

[GLENN 70]

I’m with Geoff on this  one also . Question , has any brake work been done on the car ? ,are the brakes original ? . Have the rear wheel cylinders been changed at some stage ? .

[GEOFF289]

Ok thanks for the replies. I’ll try these.

Could that also account for the rear drums braking much harder than the front disks and causing them to lock up so easily? It’s so odd that the braking pressure is uneven front to rear.

That's more likely to be a brake balance issue, either the proportioning valve has too much bias to the rear or there isn't one and the rear wheel cylinders are the wrong size.

[pgold]

Hi Rowan,
PDF attached of instructions from ford 69 Shop Manual- Push rod adjustment. I checked the depth of master cylinder with vernier caliper and made my own push rod gauge from a old credit card and stanley knife. First check pedal return as previously mentioned . If front pads still dragging I to would be checking flexible hoses as they can look good but collapsed inside and need high pressure to flow in ether direction.

[pmb0186]

Check for water in the fluid I had similar found one rear wheel locked up when warm
Replaced as a result Master cylinder, wheel cylinders, rebuilt calipers and replaced proportioning value
Sounds a lot but parts not that expensive when you diy 

[Mach ro1]

Awesome thanks for the replies again everyone!
I’ll check all of these when I go to the brake shop again this week and post back here what we find.

[Edz]

I agree with first comments, pushrod adjustment in the master cylinder. When I first got my car on the road (not a Mustang), the brakes were dragging really badly to the point they slowed the car down a lot. I pulled the pushrod out and backed it off so it was just touching, problem went away.

Read the pdf, looks like good info.

[Daz 67GTA]

My 67 did the same - front brakes seemed to "hold" after braking.. (factory Disk/Drum)
Replaced the Master Cylinder, set the pushrod correctly and they are now perfect.  For the sake of approx. $70 delivered buy a new MC from RockAuto..unless you have already replaced it