Rear calipers sticking and causing brakes to drag

[vickcraw]

I am having trouble with the rear brakes dragging on my 911T. the brake calipers were rebuilt about a thousand miles ago but about three years have passed. I recently installed a new master cylinder thinking that was causing the problem but have seen no improvement. I live near the ocean and things rust in my garage. Is there anything I can spray on the pistons in the calipers to eliminate this?

[TWJ]

Have you replaced the rubber flexible lines to the calipers? If not replace then. As the rubber ages it contracts on the inside of the lines restricting the flow of the fluid (kinda like clogged arteries!) so it cannot flow out fast enough and the brakes drag. This happened to me. Replaced the lines and life is good again!

[37yrold911]

do all of them & get the correct hoses from the dealer - I'd bet money those are TUV approved

this has to be done every 10, 15, 20 years - at least

If that doesn't fix things then you will rebuild the calipers, so start stocking up on Coleman's Mustard jar lids now

[David 68T]

Experienced the same problem some time ago on my 68T. The cause was the rear flexible brake hoses. They were full of gunk. Pressure of the brake pedal allowed the fluid to pass through under braking but fluid did not then drain back when peddle pressure released.

Agree with others. Replace the hoses and see what happens.

[csbush]

agree with the brake lines, but another option is the little metal clip held on by the pad pins. They loose tension over time, and do not push the pads back apart.

[66DC]

do all of them & get the correct hoses from the dealer - I'd bet money those are TUV approved

this has to be done every 10, 15, 20 years - at least

If that doesn't fix things then you will rebuild the calipers, so start stocking up on Coleman's Mustard jar lids now

I'm addressing this problem right now. In my case, it wasn't just the rubber hoses, but also sticky calipers, which needed to be replaced with remanufactured ones.

[vickcraw]

Replaced the rear brake hoses and bled brakes. Caliper appears to be free but after applying and releasing brakes I can feel it binding again. I will check the metal clips.

[37yrold911]

do the front hoses too - more important than rears for safety

I do see a caliper rebuild in your future

[John912]

Check your pedal assembly, make sure nothing is binding there

[VintageExcellen]

Make sure the pushrod on the brake pedal has a small amount of free play when at rest. If the pushrod is putting pressure on the master cylinder and it does not fully come to rest then you will have residual pressure left in the system starting with the rear calipers and this pressure will build up the more you use it. The brake predal pushrod should not be touching the master cyl piston while at rest. Of course all rubber lines should be changed before anything else. I doubt it is the rust in the caliper piston holding them up unless they have not been apart for 30 years. Do not put any oil or chemicals other than Silglide or brake fluid inside the hydraulic system - cross contamination of uncompatible chemicals will ruin the hydraulic system over time. Silglide is compatible with brake fluid and it is what Ate uses to lubricate the master cylinder.