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Brake/Safety PROBLEM

Any suggestions ? On rare occasions ~1/1000 miles,while at low speed 10-20mph,when I apply the brake the car starts to accelerate.I must push the brake pedal very hard to hold car from continuing to move forward.When I remove foot from brake pedal,the RPM immediately drops.Dealer cannot duplicate problem.

What year is your CTS?

We’re getting more of these posts all the time, about various makes and models. I can’t explain what’s happening, but:

When this happens you should IMMEDIATELY shift the transmission to neutral. Trying to hold the car with the brakes could cause an accident. Once in neutral you can safely steer and stop the car. Don’t try to fight the acceleration. Put it in neutral.

Sounds to me like the brake booster is intermittently not assisting the brakes and at the same time creating a vacuum leak, which raises the engine speed.

I will second circuitsmith’s diagnosis that the brake booster is failing. Next time you notice this bump the shifter into neutral and see if the engine races until you release the service brake. You might listen for a hissing under the dash above your feet – that is an indication that the air is going through the brake booster into the engine causing the speed to increase.

If you are willing to incur the expense to possibly get rid of this problem, just have the booster replaced on suspicion.

Hope that helps.

I agree with both circuitsmith and with Researcher.

Additionally, I would suggest that you file a complaint with the National Highway Traffic Safety Administration (NHTSA), via their website, stating the nature of this problem. If enough other Cadillac owners file similar complaints, then NHTSA could force GM to do a recall of the affected vehicles.

And, even if you have already paid for repairs, once a recall is initiated, you can be reimbursed for your repair expenses. You have nothing to lose by notifing NHTSA, and you could gain both monetarily and by having other potentially dangerous cars fixed by GM.

2008 cts iNITIALLY occured ~4500 mi; now occurs intermittently,possibly 800-1200 mi It has happened 12 times in 12000 mi.

I also like Circuitsmith’s theory.

With his idea in mind the shop may be able to cause the problem to recur. A vacuum gage and a wiggle on the booster line might be all it takes.

I will follow-up on the possible brake booster/vacuum leak suggestion. Thank You.