RepairPal Certified shops can diagnose and repair your 1998 Acura RL. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
Start your engine when it's still cold.
Open the radiator cap.
Check the fluid for circulation when the engine was hot (fan on)
If not, thermostat was stuck (it didn't open the valve for water go through)
Worse than that, water pump failed.