Rear brakes locked while driving

I need some help from the brain trust here. Yesterday on my commute to work my car felt like it was losing power, but then the brake light came on. Both the light for when the EBrake is pulled, followed quickly by the rear brake wear indicators. I made it to a place I could pull off the road and the rear rotors were glowing. The front brakes are fine, but the rear brakes are still close to full compression. I can move the car, but not well. What could have caused this? I was going to take it to a shop, but my guys is backed up for 1.5-2 weeks so I'm going to tackle this myself. Anyone know what I should look at first?

Both sides? Maybe parking brake is not releasing? I would check the linkage under the console first. Next guess would be frozen caliper but unlikely both sides at once. After a wash or heaving rain the e-brake pads can stick to the rotor. My car made a good crunch this morning after washing yesterday. This can also happen if the e-brake is applied when the brakes are very hot like after a track session

Does the ebrake on the 987 engage the disk brakes, or is there a drum within the system? When I stopped and pulled the ebrake it did seem to be fully engaged (no resistance or sound from handle) Was both sides though. I'll post a pic of the brakes later this evening.

The parking brake is a drum-in-hat and would not get hot enough to make the rotors glow or wear down the rear pads. Given that both rear brakes are locked up, I'd be looking at a fault in the ABS module.

I agree. The hand brake is unlikely on 987.1 . In addition to the ABS module you might look into PSM and both the ABS and PSM sensors. The systems have some overlap in their operation. A check of fault codes would be a good place to start.

@taylor15 I had a Honda Element that did the exact thing. It turned out to be the brake fluid. Somehow it got contaminated, and turned to a viscous goo. Take a peek at your fluid.

The first thing to do is flush the brake fluid. Especially if it hasn't regularly been done ( Porsche calls for every 2 years from date of manufacture.) Then proceede from there. It would likely be useful to have a diagnostics tool specific to Porsche (DuraMetric, iCarScan, etc.) that is capable of pulsing the ABS/PSM modulator. That's done while you're flushing those circuits. Big thumbs up to Zoey..

BTW - you never mentioned the year/model of your 987.. if it's old enough it's also possible some of the rubber brake lines are failing internally, and depending on how Porsche plumbs up the rear brakes, a collapsed line can cause your symptoms.

Is this a Gen2? If so, there is a brake hold function in the system for hills for PDK and I think the manual also.

Hey guys, sorry for going rogue - the week that this happened to my car I ended up being remote and then subsequently furloughed. I am going to be pulling one of the wheels off tomorrow and start trying to diagnose the issue. Since I am currently not working I am hoping that getting the fluid out will help to solve the issue, however I am prepared to possibly have to replace the booster and possibly the master cylinder if need be. The alternative is flush it, replace the pads and rotors and maybe just take it to someone if I can find someone that can work on it. Is it possible the brake hold function could have failed? What would it take to fix that? Car is a 2009 base 6 speed manual with 134k miles.

Hmm, would I have any fault codes if there are no dash lights? Other than the parking brake light coming on for a moment I have no other faults.

Don't know how it's announced. PSM uses the brakes in various combinations for traction control and counteracting over or understeer so like ABS could apply the rear brakes. The parking brake light is typically tied to more than the hand brake. A pressure difference between circuits will trigger it. Not sure what else.

Awesome! This is very helpful to know. I pretty much figured it had to be something else also, but was not certain. I’m hoping to have the rears disassembled later today or tomorrow am

Taylor15, start with the most basic steps and work your way up. You may want to check if you have the right tools before starting the work - including a vacuum pump for bleeding the brakes, hose crimps, an adjustable clamp for opening the disc brakes along with some DOT4 brake fluid (go for hi temp ones if you auto x). please also be careful with the torque on the brake calliper bolts. 1. Fluid check 2. calliper, pads and disc check 3. brake line check 4. e-brake check - e-brake is quite easy to access once you have the wheel and disc/caliper off. Only concern is the callipers may need a service if the seals are gone or the moisture has caused corrosion in the calliper. low fluid levels can also trigger the light. hope this helps!

Thank you. I have everything on the list except hose clamps. I’ll order those. Got the car on jack stands yesterday and then had to do other things around the house before I could even get started. I have new pads and rotors already so no matter the issue I will replace them. If need be I’ll also order a caliper rebuild kit as I want this to be a fully complete job. The car only has 134k on it and I plan to get at least 250k out of it so this is an important fix! For the fluid, what am I looking for?

there are a few threads on brake fluid alone - IIRC I'm running ATE Type 200 I think I'm tempted to try Motul next Brake Fluid Comparison maybe someone with some up to date changes can chime in....

I used Motul DOT 5.1 on my last two flushes. Dry boiling point 269 °C / 516 °F, Wet boiling point 187 °C / 369 °F. Not as good as the RBF 600, but absolutely no issues. But I don't track the car.