Need some direction from Brake Guys

[72T]

On my morning jaunt today, the brake pedal first went soft, then to the floor. This happened several times. The system would pump up, though, and as I tip-toed home the brakes started to function properly again. This is after I had noticed the car would first want to tack left, and then a few minutes later tack right like the alignment was changing. Maybe calipers grabbing?

The system doesn't appear to be losing fluid, the reservoir is full, but I have noticed some extra brake dust on the right rear lately. Is it master cylinder time?

Oh, it's an 87 3.2 mostly stock.

And if it is the master, I'll take any advice on best one to get...

Thanks for the direction!

[aston@ultrasw.c]

Were you driving hard or braking down hill etc?
Could be you vaporized the brake fluid.
Flush the system with new fluid.

[Bill Verburg]

Originally Posted by 72T

On my morning jaunt today, the brake pedal first went soft, then to the floor. This happened several times. The system would pump up, though, and as I tip-toed home the brakes started to function properly again. This is after I had noticed the car would first want to tack left, and then a few minutes later tack right like the alignment was changing. Maybe calipers grabbing?

The system doesn't appear to be losing fluid, the reservoir is full, but I have noticed some extra brake dust on the right rear lately. Is it master cylinder time?

Oh, it's an 87 3.2 mostly stock.

And if it is the master, I'll take any advice on best one to get...

Thanks for the direction!

brake dust is a sign that the caliper is working, if there is noticeably more on the right rear that is a sign that it is working more than the others, possible cause is a seized piston or rubber brake line that is swollen internally, either can cause the fluid to overheat which will cause the symptoms you describe. If one caliper is a problem then the others aren't far behind.

This sort of thing will be delayed by many years if the fluid is changed annually.

[KTL]

Check the calipers for ease of piston movement. You'll easily be able to tell if any pistons are hanging up.

Pedal that comes and goes is typically a master cylinder. Recently happened to my friend Mark's '86 w/original master. One day went to take it out of the garage and pedal went to the floor & wouldn't pump up at all. Hadn't done anything to prompt it, as in no work was done on the brakes prior to the problem appearing.

[porwolf]

Originally Posted by 72T

On my morning jaunt today, the brake pedal first went soft, then to the floor. This happened several times. The system would pump up, though, and as I tip-toed home the brakes started to function properly again. This is after I had noticed the car would first want to tack left, and then a few minutes later tack right like the alignment was changing. Maybe calipers grabbing?

The system doesn't appear to be losing fluid, the reservoir is full, but I have noticed some extra brake dust on the right rear lately. Is it master cylinder time?

Oh, it's an 87 3.2 mostly stock.

And if it is the master, I'll take any advice on best one to get...

Thanks for the direction!

I had similar symptoms with my 79 SC lately. Similar pedal behavior plus brake fluid loss. I had to refill the fluid reservoir a couple of times but could not figure out where the leak was, no signs under the car. Then I read about master cylinder failures here on Pelican suggesting master cylinder leakage into the brake booster. Took my brake assembly out of the front luggage compartment. Sure enough the vacuum booster was full of brake fluid. And the fluid was leaking out into the foot well. I then also noticed that my thick carpets were soaked with brake fluid also.

I would carefully check for any sign of brake fluid in the foot well, any sign of brake fluid wetness under the drain hole under the brake assembly into the foot well:

[schumicat]

unless he drove lemans it is not likely.

Originally Posted by aston@ultrasw.c

Were you driving hard or braking down hill etc?
Could be you vaporized the brake fluid.
Flush the system with new fluid.

[thumbdoctor]

Excessive humidity in the brake fluid tends to boil after many aggressive stops causing spongy feel and brake twitchiness. By all means check the master cyl for leaks too.

[emac]

72 T
Put all your money on the Master Cylinder, happened to me just last week. Same symptoms and like you I was not loosing any fluid from the M/C, what's happening is its bleeding through itself. Changed it out problem fixed. Bob Tindel (sp) has a great video posted just do a search. It was sort of a pain in the ass for me as im 63 and had a hard time doing twists and bends I havent done in years.