Where is the stopcock or release valve to drain the antifreeze to flush the system on a 1987 XJ6?

On a 1987 Jaguar XJ6, the stopcock or release valve to drain the antifreeze is typically located at the bottom of the radiator. You can find it on the driver's side, often near the lower radiator hose. To drain the coolant, simply open this valve, allowing the antifreeze to flow into a suitable container for disposal. Always ensure the engine is cool before attempting to drain the coolant to avoid burns or injury.