First, with a car this old you need to check the oil everytime you fill the gas tank. Have someone show you how to if you don't know how to, and make it a routine everytime you stop.
Secondly, if there is oil down in the spark plug hole you can (quick) fix that by pressing valve cover sealant into the gap between the valve cover and the engine block inside of the hole. The engine must be cold and you need to let the "glue" cure for 24- 48 hrs.
The tapping you hear may be simply a lack of oil in your oil pan. Check your oil level and if it is low add oil and hopefully the tapping will go away. If the oil is full or the tapping doesn't go away, your problem may be a bad cylinder or something else just as expensive. Hope this helps.
Sunday, March 1st, 2009 AT 5:31 PM