Have brake issues on 2012 Cadillac SRX - they engage at certain times for no apparent reason

S5_

I’ve been searching for others with this issue & have found a few but none with answers to why this is happening. Two GM dealers haven’t figured this out.
Happens when vehicle has been sitting in hot sun. Hasn’t happened in cooler weather. No codes in system, no lights come on the dash. Also has drained the battery if we park it while issue is happening. Issue resolves itself if you keep driving it but can take a few miles. Please ask if you need more details. I’ll be happy to elaborate.

thecardoc3

Are the brakes actually applying or do you mean that the brake lamps are coming on?

When the problem happens how long does it continue to occur? Is there something you need to do in order to make it stop happening? Or does it simply go away in it's own? How many days/weeks pass by between events?

S5_

When it happens the brakes are actually applying, feels like it’s holding the car back. It has happened for as long as 3 miles of in town driving. It goes away on its own. When it happened the first time getting on a highway, the car shook very badly like I had a flat tire. Pulled over & had it towed to a small garage. This has happened on hot sunny days. That seems to be a trigger. Brake pedal feels hard to press also when this happens. After it resolves brake pedal is softer. Have had front & rear brake pads & rotors replaced, transmission flushed. This was the dealers recommendation. It didn’t help. At least once when I drove home from first dealer (had it for a month & gave up on finding problem) my husband was behind me & said brake lights never went off the entire time. After parked took pic of brake lights on. Pulled up on brake pedal with my hand and lights went off. Next day the original battery was dead. Had been jumped at dealer to drive it home so wonder if lights were on when dealer drove it & they never noticed. Second dealer put new battery in it.
After new brakes drove it off lot & brakes were grabbing. Returned to lot, front brakes were smoking & smelled burnt.

thecardoc3

That's a great description and should assist a technician when troubleshooting the system. You have several details that are all pointing in the same direction. Once the brakes start hanging up, having a high firm brake pedal is exactly what I would be expecting to see. My routine when it happens would have me bleeding system pressure from different components. I could also use a scan tool to operate the ABS control valves in order to help isolate the cause. The fact that your brake lights were stuck on and you had to pull the pedal up to get them to go out makes the power brake booster, master cylinder, and the brake pedal linkage and brake pedal position sensor the prime suspects.

Have you checked the brake fluid level and paid close attention to the rubber seal for the master cylinder cap for swelling or distortion?

I don't advise for you to do this yourself because depending on the cause you could have no brakes for a period of time if you do and I expect brake fluid to spray out, but I would get this to act up and then crack the brake lines open to manually release them in order to prove the exact cause. I would even be ready to loosen the master cylinder from the brake booster.

S5_

Thanks for your opinions. I’m not sure it’s actually been trouble-shot at all. Both dealers drove it & said they couldn’t duplicate the issue. Then they just started guessing. I’ll pass this information on. Thanks again.

S5_

Hey thecardoc3, I should have asked - of the items you suggested to check, which ones do you think would be affected by high weather temperatures? That seems to always trigger the issue.

thecardoc3

That is quite likely that the car wasn't displaying the symptom while they had it. Without getting to investigate the problem while it is occurring there would be no proof that anything they did would be the correct repair. How likely is the problem to occur on any given day?

Another strategy would be to take it to a shop the next time it happens while it is still occurring. Make sure to describe the symptom exactly as you did here and include the frequency of the events. Include other details like how long (time and distance) the car is driven to get the symptom to occur. Stress the need for a technician to start investigating the issue before it goes back into hiding again.

One thing to understand is that the technicians don't get paid to drive the car around hoping to get it to act up. The shop would have to charge for that time in order to pay the techs to do it. So, the car either displays the symptom on a typical road test or it does not.