Chevrolet Motor Mounts
The Center for Auto Safety is the nation’s premier independent, member driven, non-profit consumer advocacy organization dedicated to improving vehicle safety, quality, and fuel economy on behalf of all drivers, passengers, and pedestrians.
On December 4, 1971, General Motor (GM) announced it would recall over 6.68 million 1965-70 Chevrolets with defective engine mounts. The recall covered 1965-69 full-size Chevrolets, 1965-69 Chevy II’s and Novas, 1967-69 Camaros, and 1965-70 Chevrolet/GMC light trucks, all with V8 engines. (NHTSA Recall 71-0235, now 71V-235.)
Engine mount breakage causes a self-perpetuating chain of events. When the left-side mount breaks, engine torque causes the engine to rise up, pulling open the accelerator linkage; this causes even more upward movement, and consequently more opening of the accelerator linkage, until the engine’s movement is stopped by the closed hood. Moreover, the engine’s upward movement pulls the power brake booster vacuum hose loose, thus greatly increasing the force needed to stop the car. Also, the automatic transmission “PRNDL” quadrant would shift itself over one position to the right (e.g., from D to L), affecting all gear positions; this meant that the car no longer had a Park position, and could be started in Reverse.
The National Highway Traffic Safety Administration (NHTSA) received its first report of a broken Chevrolet motor mount in September 1969, and contacted GM a few weeks later. However, even before it received GM’s reply that indicated a total of 14 reports on 1968 models Chevrolets alone, NHTSA placed the investigation on “inactive status.” NHTSA informed GM of this “inactive status” in a June 1970 letter.
The case (IR 162) remained in abeyance until NHTSA received a second report in late August 1970. Only then did the agency begin to arrange independent tests of effects of broken Chevrolet motor mounts on driver control, but even these tests (in October 1970) were flawed. The test facility used a Chevrolet without power brakes or power steering, thus preventing an examination of brake assist loss. Nonetheless, the tests demonstrated the throttle-opening effect that consumers had noted.
In December 1970, NHTSA sent a second, more comprehensive information request to GM. The company’s January 1971 reply indicated a total of 172 reports of failed motor mounts, with 63 accidents and 18 injuries; GM also advised that it had been using the same mount since 1958. Despite this clear indication of a widespread defect, NHTSA did nothing further on the matter until June 1971, when it sent questionnaires to 63 consumers who had reported broken Chevrolet motor mounts. NHTSA sent a third information request to GM that August. On September 1, 1971, Ralph Nader sent an extensive letter to NHTSA about deficiencies in NHTSA’s investigative procedures, including the handling of the motor mount defect. Robert Irvin, long-time automotive writer for the Detroit News, took interest in the matter after receiving a copy of Nader’s letter, and subsequently wrote over 70 articles about the motor mount case. Irvin’s articles, many of which appeared on the front page played a key role in putting public pressure on GM and NHTSA to force a recall.
On October 15, 1971, NHTSA issued a consumer protection bulletin advising motorists of the “potential risks” of broken GM engine mounts. Around this same time, GM President Edward Cole declared that a broken mount was the equivalent of a “flat tire or blowout”, and that anyone who could not control a car with a failed mount at 25 mph “shouldn’t be driving.”
A few weeks later, NHTSA sent two staff members to GM’s engineering facilities in Warren, Michigan to witness more tests of failed motor mounts; their findings corroborated the results of the earlier tests. Around this same time, NHTSA Administrator Doug Toms visited GM headquarters and test drove Chevrolets with severed mounts with GM President EJ Cole in the test vehicles, but NHTSA did not place a record of Toms’ visit in the public files.
NHTSA sent a letter to GM on December 1, stating that it was close to determining that a motor vehicle safety defect did exist. Three days later, GM announced its recall, but the company refused to admit that the vehicles contained a safety defect.
One irony of the recall is that on over 95% of the vehicles recalled, GM did not replace the defective mounts themselves, but rather installed a bracket and cable to restrict engine movement if a mount broke. By avoiding replacement of engine mounts on all 6.68 million cars, GM managed to cut its recall costs considerably; the cable and bracket assembly cost about $1 per car, far less than the $50 cost of new motor mounts.
For a comprehensive report and materials on the failure of NHTSA to obtain a more timely recall, see Hearings on Auto Safety Repairs at No Cost, Senate Commerce Comm, 93rd Cong., 1st Sess. Pp 200-58 (Jan. 30-31, 1973) including Oct. 11, 1972, letter from Chairman Harley O. Staggers, House Interstate & Foreign Commerce Comm. to NHTSA Administrator Douglas W. Toms.