ALLENTOWN, Penn. – Mack Trucks, Inc. has agreed to recall certain model year 2008-2022 Mack TerraPro (MRU and TE) trucks which may have a malfunctioning parking brake and has resulted in several reports of crashes and/or injuries as well as a “stop delivery” order issued Dec. 6.

According to the National Highway Traffic Safety Administration Part 573 Safety Recall Report 21V-953, the 21,641 trucks within the recall population were built with a PP1 valve fitted with an exhaust fitting and tube.

The report described the defect as, “A worn PP1 valve (park brake control valve) exhibiting an internal leak may cause air to pass through and out the exhaust port when the park brake is applied. Under certain conditions, the internal leak in combination with the installation of an exhaust hose may result in back pressure sufficient to allow the park brakes to release.”

The report further explains the issue of the TerraPro in simple terms: “Potential of a vehicle rollaway with the park brake control valve in the on/applied position, which may result in a vehicle crash, property damage and/or personal injury.”

According to NHTSA there are two consumer complaints, three field reports, and five reports involving a crash and/or injury.

The remedy will be removal of the exhaust tube and fitting from the valve.

Dealers were scheduled to begin receiving notification of the recall Dec. 17. Owners are scheduled to begin receiving notification Feb. 4, 2022.