I have noticed that the brakes on my '83 tend to fade. I will keep a constant pressure on them and the pedal will slowly sink. The pressure will build up again if I mash the pedal again. It almost feel like there is a leak. I have checked overy connection and I am not loosing any fluid. I flushed the system today and replaced the old fluid with Castrol GTLMA thinking this would remedy the problem. But it still does it. I can sit at a stop light and watch me foot sink to the floor steadily. But, like I said, if I pump them up again, I get full pressure.
What could be causing this? Do I need new calipers?

Thanks!

 

Your master cylinder is the culprit. Fluid is leaking past the seals. If you think there should be fluid loss , there wont be. You can buy kits or just replace the master cylinder.
I have replaced the master cylinder on my 68 mustang about 8 times now. So i know master cylinder issues.lol.

 

Sounds like the master cylinder. The seals on the piston are bad causing fluid to leak around them which causes the pedal to slowly sink under constant foot pressure. Rebuilt master cylinders aren't too expensive.

 

Zedex, funny you mention 68 Mustang master cylinder. My 68 did the same thing leaving me with no brakes in rush hour traffic

 

One more here suporting the MC need to be replaced.

Good luck
Jeremy

 

Got a pic of your car Dryheat?

 

my 67 mustang's brake are inadequate at best. non-power, drum all around. yeah, scary in traffic. anyways, be sure there arent any air bubbles trapped anywhere in your brake lines, sometimes air can get into the master cylinder really easily when the top is taken off. bleeding the brakes never hurts, and if it doesnt help, then you know for sure that its the cylinder.

 

My 68 has power disk brakes. They work pretty well i guess. But not like new cars thats for sure. I think i have replaced or rebuilt everything on that car in my 17 years of owning it.
Your best bet Haveblue is to replace the master cylinder and be done with it. Master cylinders develope pits in the casting from moisture. alot of times a kit will only last you a short period of time or wont help at all if the cylinder has pits.You would have to hone it out and then get a kit.Better off buying new. Thats why replacing your brake fliud in the whole system every few years is a good idea.

 

No more 68 mustang, Got sold to a teenager who quickly wrapped it around a telephone pole. I still miss that car.

 

Yup. Thats a common story. Sorry to hear about that. Way back when my dad owned a few mustangs. restored them. Sold a real nice one that lasted a few weeks till it was totalled.
Mustangs are nice but can be a real PITA.

I compare my mustang to a beautiful woman. It feels so good driving her but she nickel and dimes you to death.

 

HaveBlue:
I've got the same fade on my pedal and my fluid is dirty as hell. Looks like I need a MC also. I just bought this truck too

Two questions for all y'all:
1. Who has replaced theirs or knows how easy of a job it is. Tips?
2. Anyone have some online recomendations as to where to buy one?

Thanks.
-Stu.

 

Picked up a remanufactured MC from Auto Zone today. It was $21.99 + $18 core. I'll replace it tomorrow and get my $18 back.

 

Good deal and good luck. Let me know if you come across any hang-ups
-Stu.

 

My, how prices change. I just looked up a master cylinder for my truck, as the seals between the reservoir and cylinder are leaking. Autozone = $49.88 ($50 core), NAPA $48.99 (33.75 core). Too bad you can't just get the seals.