My son drove home from College Friday night and complained that his 1981 240D seemed to stumble on acceleration. I went out to take a test drive and the Glow Plug light did not light. The next morning I tested at the Glow Plug Relay with a VOM meter and discovered two glow plugs bad. (#3 & #4). When I took out the plugs to replace them the tips were burned to half their size. These plugs were less than 6 months old. I replaced them and the car started but had a bad knocking sound. I checked all the valves and then noticed that the Injectors (# 4 & # 5) were leaking at the base but not where they thread in. They were leaking actually outside the pre-chamber retaining ring. I double checked to ensure that it was not leaking from the return lines. I have pulled all the Injectors and intend to have them tested at a Diesel shop tomorrw. My question is, could bad injectors seals cause this leaking ? If not the seals, could a bad injector cause it ? I have done many searches and can't find this particular problem. Anyone have any ideas ? Thanks in advance.