Low Pedal On My 1968 mustang

by Paul
(BC, Canada )

Low Pedal Brakes:

What is the cause of my low brakes, I bled all the lines , replaced the Master Cylinder,and the brakes go atleast 3/4 of the way down before I stop.

My mechanic says that's normal for these old cars.

I find it hard to believe that's the way they are. This car was converted from drum to disc, so I'm just assuming a incorrect part installed or something.

Thanks Paul


Hey Paul!

My first question for you, is whether the new 1968 Mustang master cylinder is incorrect. There are different ones for different applications.

For instance, the master cylinder for drum brakes is different than for disc brakes. There's also a different master cylinder for power brake cars. So if you don't have the right one, you can have issues with things like stroke length, bore diameter and more.

Also, check things like the proportioning valve and if all of it checks out to be the right parts, the usual most common issues are going to be either not all air has been bled from the system (re-bleed the system, starting from the longest brake line and move forward).

Other issues to check, that can cause low pedal on your 1968 Mustang are if your rotors are not new, include making sure that they are not less than the minimum thickness.

If they are, they may still stop your Mustang, but the pedal travel will move down, every fraction of a millimeter that the disc wears.

Do the same for the rear drums, also making sure that the issue isn't as simple as the rear shoes are not adjusted properly. Same thing goes with the drum diameter if they are not new drums.

Hope that helps!

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Low Pedal On My 1968 mustang
by: Paul

Hi B
Thanks for your input, sorry it took a while but I had other issues with my engine and had to rebuild another one, so much for number matching.

I did find a 68 block from a Cougar, bought the whole car, and used the engine ,unfortunately the Cougar was a rust bucket.

Anyways still have the issue with my brakes so I'm thinking a total rebuild and replace booster to and calipers and shoes, I'm hoping that this will do it, I even tried to slightly extend the booster rod, a couple times and I thought that did it but it ending up the brakes were pressing on there own and while riding brakes got extremely hot......so that didn't work. so that the plan for now to rebuild the whole system. Thanks Paul

Hey Paul

I am getting to think this is an issue with both the Mustang and Cougar. My son has a 1968 Cougar (also rusty) and this seems to be a common problem. We did notice that the whole system seems to be very sensitive to all parts bleeding out properly and have basically gone the entire rebuild route as well.

Front calipers had to go several rounds to get the last of the bubbles out. Typical bleeding issues tend to go from the longest brake line having the most likelihood to being the culprit, but this wasn't the case for the Cougar.

I haven't had this issue with earlier Mustangs. They seem to bleed just fine.

Rotor thickness and drum thickness are also big ones. Losing metal off both sides of the rotors or thickness on your drums can increase pedal travel and make for a low pedal.

By the way, your pedal travel should be 1.85 inches for both the Mustang and the Cougar.

Pedal free height is 5.3 to 6.2.

Rear Drum Adjustments:

The other area that can have a direct effect on travel or low pedal is proper adjustment of your drums. If the friction material is too far away, you will have a low pedal and risk overheating and cracking the linings from the force against the drums when they make hard contact.

Good Luck!


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