brake problem on 73 E

[cmcfaul]

The brakes on my 73 911 E drag excessively after a couple hard stops. The peddle gets rock hard to the point of dragging the brakes. It's like they get pressurized during braking but then don't release the pressure. A hard pedal is usually a good thing but this has gone way too far. Not sure if it's a heat issue or master cylinder. I replaced the master cylinder a few year ago. The brakes are otherwise perfect, no pull or unusual bias front to rear.

The fluid is two years old and is the blue racing type. I changed it last exactly two years ago before my last track event. (hoping to do another this year)

I pulled into my garage last night with the brakes dragging and the calipers were evenly (all four) warm to the touch but definitely not hot (I am assuming not hot enough to boil fluid).

I replaced the rear rotors last week and thought the problem might be an e-brake over heating or something wrong inside there. No, everything was perfect.

The pedal gets so hard that I am sure the brake light does not even come on as the pedal moves barely at all when braking with this problem.

I can free the brakes up by pushing hard on the brakes while standing still and releasing the pedal. The car then rolls freely but the pedal is still hard as a rock and the next stop Will cause them to drag. I parked the car with the brakes in the dragging state. This morning they were fine until I did a couple hard brakes and the problem persists.

Thanks in advance,

Chris
73 911 e

[LakeCleElum]

Chris - I had the exact problem with my '73 T a few years ago and recently on my '69 T. In both cases, it was necessary to replace the soft brake lines. They look fine, but get rotten from the inside and can get plugged to the point you can't blow thru them with 100 blk of pressure on an air gun.

What happens is you excert more force than that by stepping on the brake, but you are just relying on the rubber seal in the caliper to push the piston back away from the rotor. The pressure just doesn't release.

To confirm, next time they are dragging, quickly pull that wheel and open the bleeder. If you get a little fluid squirting out, you know the pressure was not released.

Just passing on some info I got from some kind folks here on Pelican...G'luck..

[cmcfaul]

Replaced the brake lines about 7 years ago. They are the braded steel type. Your theory sounds solid. I will replace the line and see what happens. Not sure if I ever replaced the rear lines. Guess I should do all 4.

Thanks,

Chris

[Bill Verburg]

It could be brake lines that are swollen internally

Could also be the square caliper piston pressure seals, when nominal they deform when the brakes are applied, then when the brakes are released they return to their square shape dragging the piston back off the rotor.

Could also be a plugged relief port in the m/c