Tech Tip: Cadillac brakes lock up after fluid top-off

The owner of this CTS said that the brakes locked up and wouldn't release. The problem occurred after he topped off the brake fluid.

Richard Diegle

Related To:

ALLDATA

April 29, 2022

Vehicle: 2008 Cadillac CTS, RWD, V6-3.6L, Automatic Transmission/Transaxle

Mileage: 168,265

Problem: The owner of this CTS said that the brakes locked up and wouldn't release. The problem occurred after he topped off the brake fluid.

Case Details: The technician’s initial checks found that the brake fluid looked contaminated with debris floating in it. The master cylinder cap seal was swollen, and master cylinder appeared to have been leaking onto the booster. An ALLDATA Tech-Assist consultant recommended finding out what kind of fluid the vehicle owner used. If it was anything other than an approved brake fluid, then everything in the brake system with rubber in it (hoses, calipers, master cylinder, ABS module, etc.) would need to be replaced, and the hard lines flushed. A call to the owner revealed that he had topped up the brake fluid reservoir with power steering fluid.

Confirmed Repair: The technician replaced the master cylinder, calipers, rubber hoses, and flushed the entire brake system, including the ABS components. A lengthy road test verified the repair.

Reprinted with permission from ALLDATA

About the Author

Richard Diegle

Senior Automotive Editor for ALLDATA

Rich Diegle has been in the automotive industry since 1978. After graduating from a local community college, he began working at a Nissan dealership as a used car technician. Since then, he’s worked as a Nissan and ASE master automotive technician, shop owner, marketing copywriter, automotive editor, public relations manager, instructor, ALLDATA Tech-Assist team manager, and a senior automotive editor.