James S. Milloy Jr., 53, advertising executive and part owner of Milloy Dodge of Mannasas, Va., died Sunday in a Coral Springs Fla., hospital following a heart attack.

Born in Minot, N. D., Mr. Milloy moved to Washington in 1933, and attended the University of Maryland. After holding several jobs in the advertising field, he founded the Milloy Advertising Agency of Washington in 1953, which he operated for four years then sold.

Mr. MIlloy was a general sales manager for several Washington automobile dealerships before establishing Milloy Dodge of Manassas. Va with his brother in 1970. Since 1974, when he moved to Florida, he has been involved with a proposed expansion of Milloy Dodge in southern Florida.

Mr. Milloy was a member of Manor Country Club and the Bethesda Country Club.

Survivors include his wife, Dorothy, of the home in Coral Springs, Fla.; seven daughters,Karen, of the home, Janet Luxford, of Oakton, Va., Judith Fllison, of Centreville Va, Jerrie Spore, of Centreville; JIll Ray, of Chantilly, Va., Jacqueline Longerbeam, of Sterling. Va., and Jennifer Milloy, of McLean; two sons , James S. III, of Herndon, and Jeffrey M., of Mclean; two brothers, Peter B., of bethesda and Richard P., of upper Marlboro; a sister, Kathleen Pope, of Bethesda; and 12 grandchildren.