With 84,000 miles there suddenly appeared a loud tapping/knocking\nsound from the #5 cylinder upper engine area. No smoking, reduced\npower, tapping is reduced slightly under load. Engine has only been\nidled since noise began. There was no warning , the noise appeared\nsuddenly. I have checked the plug and coil and am about to remove\nvalve cover to inspect. It would seem to be coming from the Valve area\nof the head but my experience shows very little in this area would\ncause the loud knock. Has anyone experienced such symptoms before with\na Volvo 5 cylinder turbo?