1970 911T rear brakes grabbing.

[924CarreraGTP]

My car has been sitting for three years. After getting it running, the rear breaks are getting very hot and making a high pitched squeel. The light in the top of the oil pressure guage stays on all the time. The Emerg brake is down but the car seems to dragging at higher speeds. I believe it to be just the back brakes. Any suggestions on where to start?
The rotors and pads look good.
Thanks,
Justin

[johnsjmc]

Jack up the rear and see if you can turn the wheels. If you have driven a short distance and the rear rotors are hot then it,s likely the calipers sticking. If the wheels are hard to turn and the rotors are normal temp then the parking brake mechanism is sticking. Rebuild calipers and or dismantle and clean /lube /replace parking brake parts as needed.

[Zendalar]

I would change the rear flexible brake hoses anyway. Its a cheap thing to do, and easy usually.


Oh, while you are at it, change the front hoses as well, you have to air the system anyway.

[Grady Clay]

Justin,

This is one of the normal consequences of letting a car (not just 911s) sit for extended periods.

On a 911, the usual (and prudent) procedure is to ‘go through’ the entire brake system, all at once.
If you don’t, you will end up doing the entire system piecemeal and possibly have dangerous situations in the process.

You should replace the master cylinder and all four flex brake hoses.
You should remove the pads and lightly sand the friction surfaces and sides or peplace with new if necessary.
You should inspect the rotors for damage and measure thickness and sand the friction surfaces lightly or replace if necessary.
You should cycle the pistons (one-at-a-time) in the calipers, noting if they operate freely and no signs of leakage. Rebuild the calipers if necessary (pair or all four only).
In your case, remove the rear rotors and clean & inspect the parking brakes. Adjust as necessary.
Inspect the operation from parking brake handle through the brake shoes moving.
It is not unusual for the parking brake Bowden tube plastic support/guide (on the trailing arm) to be broken.
The cables were liberally greased (inside the Bowden tubes) when new.
Bleed the brakes with the best new fluid.

Note my emphatic “should”.
It is common for a 911 that has been sitting to have the master cylinder start leaking suddenly, after it has been back ‘in service’.
This has fluid leak out on each application of the brakes without any indication of a problem.
Then there is an “Oh NO!” application of the brakes with no fluid and no brakes.
Been there myself and seen too many accidents and ‘close calls’.

Be careful to not bend, twist or damage the steel brake lines. Use lots of penetrate (PB Blaster), two proper wrenches and patients.
Reassemble with some heavy (wheel bearing) grease between the fitting and the steel pipe.
Make sure the fittings are tight without any ‘twist’ in the flex hoses.
Use standard OEM rubber flex hoses and not aftermarket SS covered hoses.

When you install the two supply hoses in the master cylinder, remove the hoses and reservoir from the car and insert the tubes and rubber seals in the master cylinder on your workbench.


The ‘while-you-are-there’ projects are:
Cleaning and re-greasing the front wheel bearings with new seals and O-rings.
Replacing the pedal assembly bushings.
Inspecting everything you can see.

Best,
Grady