Joe:

I figured that the IP seals were a good bet since the compression was OK (marginal in #4), the injectors were clean and set properly, and a leakdown test showed ring leakage but no valve leakage. All work performed for previous owner while I was discussing purchase, all done by Hans (my indy mechanic and source of MB knowledge). Much cheaper than an engine overhaul, although that may still be in the works.

There are several causes of injection knock at idle -- low compression, late fuel delivery, and sticky injectors being the most likely.

Before I dived into the IP I'd get the valves right -- you might want to set them a little loose for a week or so, then recheck in case they are carboned up. As the compression comes up, the carbon will burn off, and the valves will go tight again. 60,000 miles without an adjustment is a LONG time for this car! Get some known good fuel in it and drive a bit before making any more changes. Find some RedLine or similar fuel treatment and run that through -- if it cures the knock, it's just nozzle carbon.

If the above doesn't fix the problem -- and you will know pretty soon when you do the valves -- if any of the exhaust valves have less that 0.010" clearance cold, your compression will be low -- loosen the cap nut at the injector one cylinder at a time and locate the offender, then try just snugging up the pressure valve holder.

If everything seems fine, then replace the pressure valve holder seals. I spent $7.56 for the entire set!

Compression check isn't too hard, just don't squirt oil in to check the rings for leakage -- it can ignite, or worse, if you get too much in there, bend a rod! You will need a gauge good for at least 500 psi and the appropriate adapter. Otherwise, same as for gas engines.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!