FRANKFURT, June 29 - German luxury carmaker BMW said on Friday it had recalled about 22,000 cars mostly in the United States due to a potential problem with the cooling system thermostat. "We have recalled about 22,000 vehicles for tests," said a spokesman, who added that the recall would affect some cars in Japan and elsewhere. He said he expected about 100-200 cars to be fitted with a new thermostat as a result. "There is no potential danger from this and it doesn't affect the engine," added the spokesman. He declined to say how much the recall action would cost. The problem affected vehicles with a four or six cylinder engine built between October 1998 and March 2000, he said.