HYUNDAI Motor Co, South Korea's largest carmaker, is learning a painfully expensive lesson about carmaking: no bumper, no car. On May 3, Hyundai took the unpleasant step of halting its assembly production lines in Seoul, thanks to a labour walkout at Apollo, a medium-sized Korean car parts supplier. That company happens to supply about 90 per cent of the front bumpers and back-side lamps used in Hyundai's Excel, Elantra, Sonata and Grandeur models. Since then, Hyundai has been watching about 30 billion won (about HK$279 million) a day in sales vanish into thin air, according to investment bank Barclays de Zoete Wedd. From yesterday, the production disruption, which involves 4,000 cars a day, will start to cost Hyundai valuable export business in the United States, Europe, and other Asian markets. ''Unless the strike is resolved, we will not be able to meet our export schedule,'' said Mr Im Jong-hun, a spokesman for Hyundai. The production shutdown could not come at a worse time for the company. Analysts are hoping that this year will be a comeback year for the carmaker. Last year, a nasty two-month strike by its own workers sent the company's earnings into a tail-spin. The labour troubles were costly. Hyundai's net earnings during the last fiscal year plummeted 22.6 per cent to 41.6 billion won on six trillion won in revenues. Since the production halt on May 3, Hyundai shares have shed two per cent of their market value, down 800 won to 27,800. Investors have reason to fret. Hyundai is now sitting on the sidelines just as the Korean car industry is showing signs of life. The rapid appreciation of the yen this year against other currencies has improved the price competitiveness of Korean carsand computer chips. And that has given a big boost to Hyundai and the country's other top carmakers such as Daewoo Motor Co and Kia Motor Co. Consider that during the first quarter of this year, Korean car companies posted an increase in exports of about 133,000 units, up some 92 per cent over the year-ago period. Leading the pack was Hyundai, which exported 81,000 of that total. Hyundai is hoping that the labour strife at Apollo will be settled quickly. On April 30, some 700 factory hands at the company stormed off after failing to win their demands for a 21.8 per cent pay rise and more participation in management. ''The workers must go back to work first and then we will negotiate,'' said a company spokesman at Apollo, ''and we believe they will in a couple of days.'' In the meantime, Hyundai will scout around for other suppliers. One possibility is Lucky Ltd, an affiliate of the Lucky-Goldstar business group, which already supplies Hyundai with some rear bumpers. However, the company has limited production capacity and is unable to make up for all of the parts that would have been supplied by Apollo. Until Hyundai gets back on track, its vital export business with the West could be in jeopardy. The carmaker hopes to sell more than 60 per cent of its exports in foreign markets this year. North America, alone, represents some 35 per cent of total sales. All told, the strike could ruin what the industry hoped would be a banner year. ''Any unexpected labour strike like the one at Apollo will not help South Korea meet its export target of 522,000 cars this year, up per cent from last year,'' said Mr Cha Nam-jin, a manager in the international business department of the Korea Automobile Manufacturers' Association.