Let It Bleed: General Motors Recall Targets ZF Brakes

General Motors has recalled over 210,000 late-model sedans and crossovers in the U.S. and over 19,000 north of the border after discovering the potential for a braking issue. The automaker blames the issue on rear brake calipers supplied by ZF, which can also be found on vehicles built by Volkswagen, BMW, and Audi.

It all comes down to trapped hydrogen gas in the body of the brake piston, which, when released into the brake fluid, makes for a mushy left pedal and reduced rear brake performance.

GM claims it was first notified of the issue by dealers after certain vehicles failed pre-delivery inspections. On June 14th, days after the automaker opened an investigation into the issue, ZF, which had already notified the German brands about the potential problem, alerted GM. The supplier had failed to properly chrome and temper the pistons, with the potential for small amounts of hydrogen to remain inside the piston bodies.

The automaker claims all of the gas would be released into the brake system within 23 days of assembly, but drivers would notice it after 15 days.

Included in the recall are 2018 and 2019 model year vehicles, among them the Chevrolet Cruze, Equinox, Malibu, Impala, Volt, and Bolt, as well as the GMC Terrain, Cadillac XTS, and Buick LaCrosse.

The obvious solution is for a technician to bleed the brake system and release the gas. GM claims it isn’t aware of any crashes resulting from the issue, and that 306 of the 375 warranty claims it received by the 23rd of August were for vehicles that hadn’t yet been turned over to owners. All of the faulty pistons were installed before July 17, 2018, it added.

[Source: Safercar.gov, via Automotive News] [Image: General Motors]