"The strike started today at all the seven car manufacturing companies across the country," said Mpumzi Matungo, the treasurer of the National Union of Metalworkers (NUMSA).
The workers are demanding at least a 14% pay increase, but employers have offered 8% with effect from July 1.
"That has been rejected, and that is why the workers have gone on strike," he said. “It's an indefinite strike."
Workers at BMW started striking last Thursday.
"We are not producing cars at all," said Guy Kilfoil, the BMW spokesman.
The sector contributes about 6% to the country's GDP and accounts for roughly 12% of the country's exports. Last year, South Africa exported 277,893 cars, including to the European Union market.
Work stoppages are common in South Africa in the middle of the year, when collective wage negotiations traditionally get underway.
Wage talks are also taking place in the volatile mining sector where dozens were killed in labor unrest last year.
Despite being the largest economy on the continent, South Africa is underperforming compared to other fast-growing countries in the region, expanding only 0.9% in the first quarter.
Last year the country registered a meager 2.5% growth, hit by the effects of the post 2008 global financial meltdown and the eurozone recession.
Copyright Agence France-Presse, 2013