brakes binding

I'm just beginning to drive the '83 911SC that I've spent two years restoring and upgrading--short carburetor-tuning runs (PMOs) right now--and one problem I'm noticing is that after driving a few miles, the brakes begin to bind. (Doesn't happen if I don't use the brakes at all, but if I use them normally, it does.) They're by no means locking, although maybe they would start to if I drove farther, but when I get back to my driveway and stop on its maybe-five-percent grade, the car doesn't roll back, which it would normally do. All four wheels and calipers are equally warm. After the car cools down some, the car will roll back easily. Any idea what's causing this?

Stephan

Stephan,

Old rubber hoses can swell internally and act like one-way valves, not allowing all of the pressure to bleed off. If you haven't replaced them in the course of your last two years' work, that should be your next project! Of course, rebuilding the calipers at the same time would be easy and logical, too.

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Warren Hall
1973 911S Targa

Stephen,

Sounds like a good time to:

1. Replace all the old rubber brake lines if they are factory units or more than 8-10 years old.
2. Flush out all the old brake fluid.
3. Overhaul all four of the calipers if the problems remains.

Sounds like one or both of the pistons on the calipers could be sticking... but on all four wheels? I would wonder if something else is going on. Could be one or two of the pistons sticking in separate calipers and feeling like all four wheels are locking up. Wonder if you might have a brake hose collapsing internally and not releasing the fluid to the caliper, thus causing the drag on one or more the wheels.

Also, does the brake pedal seem to return normally, and all the way to the stop after you apply it? I have had the master cylinder leak and cause the pedal assy to get sticky. This could cause the brake pedal to remain with some pressure in the system even when you take your foot off of the pedal, and keeping pressure in the brake system.

The rotors and calipers should be warm but the car also should be able to roll easily after driving it.

Hope this helps,

JA

I suspect the brake lines as well, maybe in conjunction with bad seals and/or some rust at the calipers.

Once you change your rubber brake lines,
make sure to closely inspect/change the connecting hoses between the fluid reservoir and the plastic lines running to the master cylinder.
Nothing which will cause your problems, but annoying to bleed all brakes again having forgotten those 4 inches.
Guess how I know

Jens

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Since the brakes at all four wheels are warm, I'd check the pedal for proper return to rest. Sounds like something, could be crd from brake fluid and dust, or somethind that has dropped into the wrong spot. Good luck.
Les

fix it now! you don't want to be on the side of the freeway waiting for the flatbed. ask me how i know.
bob
'68 911L with newly rebuilt calipers all around, hoses, pads, master cylinder, etc.

[meichten]

I’m having the same issue 80 SC, new rear calipers, new MC, all steel lines about 10 years ago from PO. Bled the lines after putting in the new hardware. I can go out for a drive, after about 5-10 minutes the pistons are not releasing. Get home and bleed one of the calipers and they are able to release and fine for another drive.

I’ll will post a new thread with this issue, just curious what the resolution was in your case? Thanks

[AG81]

Just replace my front and rear brakes with all new parts. Used existing calipers after cleaning and powder coating very very carefully. Everything else is new. Pistons, pads, pins, seals ect. ALL NEW.

Experienced some of the same issues as you. Pumping the pedal helped during break in, which is still going on. After speaking with a certified porsche tech I know this seems to be a normal break in situation.... No other explanation was given. He advised to drive and use them.

[meichten]

Thanks AG81 I’ll keep driving for now.

[trond]

if all 4 wheels I would guess bad master cylinder OR linkage ajustment. All 4 hoses should not be bad

[Targalid]

I replaced all four rubber brake lines. Takes about an hour. Cheap.

[Trackrash]

Originally Posted by Targalid

I replaced all four rubber brake lines. Takes about an hour. Cheap.

+1. As mentioned old rubber brake lines which will cause this issue. AHIK.

Early_S_Man's legacy lives on....