Vehicle recall 78V030000 · February 9, 1978

Mack RL, RS and 2 more models

A design deficiency exists in the air dryer piping in the area of the pressure relief valve and compressor governor control link.

Source: NHTSA data as of September 22, 2026. Last refreshed Sep 23, 2026, 2:43 AM UTC.

Summary: A design deficiency exists in the air dryer piping in the area of the pressure relief valve and compressor governor control link. Moisture is passed and builds up in this relief valve and control line. In freezing ambient temperatures, this moisture may freeze, allowing the chassis air system pressure to exceed 150 PSI. Excessive air system pressure can cause separation of air piping connections and air system valve failure.
Remedy: The dealer will relocate the air system compressor governor line and pressure relief valve to eliminate moisture accumulation.
Notes: Vehicle description: trucks equipped with anchorlok air dryers.system: service brakes; air system and governor control line (air dryer).consequences of defect: when this occurs, automatic application of the chassisemergency spring brakes and trailer brakes could cause loss of vehicle controlwithout prior warning and a vehicle accident.note: owner/driver is advised not to operate vehicle if air pressure EXCEEDS15O PSI.

Recall details

NHTSA campaign: 78V030000
Reported to NHTSA: February 9, 1978
Filed by: MACK TRUCKS, INCORPORATED
Owner notification: August 23, 1978
Vehicles potentially affected: 400
Initiated by: the manufacturer
Components: Service brakes, air › Supply › Hoses, lines/piping, and fittings

Recall 78V030000 on nhtsa.gov, with the manufacturer’s documents

Vehicles covered

As listed by NHTSA. A recall usually covers only some vehicles of each model and year, often a production date range.

Mack RL (1975-1978): 1978, 1977, 1976, 1975
Mack RS (1975-1978): 1978, 1977, 1976, 1975
Mack WL (1975-1978): 1978, 1977, 1976, 1975
Mack WS (1975-1978): 1978, 1977, 1976, 1975

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