[Vwdiesel] Smoke and engine flushing?

[George Allison]

 guess I'm what you'd call a pretty frustrated VW diesel owner. I have been subscribing to this mailing list for a few months and reading the info here with interest. I have some problems with my car that I have been trying to diagnose, and I've talked extensively to a lot of knowledgable people, but I am running out of answers, so maybe some of you can help me...

My car is a 1981 VW Rabbit with the 1.6L NA diesel motor. The PO said it was rebuilt about 90k ago, and apparent compression and notes regarding cyl. head retorquing times support that claim (I will soon be verifying compression but I'm almost certain it is good because it starts well even if I don't use the glowplugs in the morning). 

My continuing problem concerns the car's smokiness. As stated, when cold it starts right up, and does not smoke. As things warm up, the smoke starts to appear; by the time it's fully warm, the smoke is quite bad and occurs at all times, even at idle. It's worst when climbing a hill, accelerating, or when moving off from a stop after idling for awhile, like when leaving a red light. I have confirmed, by having my dad drive behind me and watch the tailpipe, that it also smokes even when there is no-load coasting, like when going downhill in 2nd gear at 25 mph with my foot off the accelerator. The smoke is quite embarrassing and worrisome, not to mention polluting. Its color is a light-blue/silver, and it even occurs pretty heavily when idling at a stop. 

I have been told that this kind of smoke results either from unburned fuel or from burning oil. I think I have the fuel burning question solved, what with having replaced the injectors, set cam and pump timing when I replaced the timing belt, replaced the fuel filter, checked the fuel lines for air, and adjusted the valves. 

That leaves oil burning, which makes more sense anyway because fuel smoke is worse when cold, whereas oil smoke occurs more when warm, like it does in my car. Also, my car has used a pretty significant amount of oil since I've owned it, which tells me something. From what I've read it sounds like either the valve guides have failed or the oil rings have gone bad. Is there any other way oil could get in besides the headgasket--could a worn vacuum pump, for instance, be the problem somehow? I think at the end of the day I will have to re-ring it, but one more idea I got from my biodiesel man (who owns a Volvo diesel, basically a bigger VW diesel if you didn't know, and said this worked for him) was trying to clean the sludge out of the engine some. He said when he first got the Volvo used it smoked as badly as mine, even at idle, and after running synthetic oil in the engine and biodiesel in the tank for awhile it cleared right up. He even said a lot of people run straight biodiesel in the motor for a few minutes to clean things out. Now that sounds a little wacky to me, not to mention a little hard on the engine, but is there any good engine flush/cleaner chemical you guys recommend? Restore, ATF, Lucas, Seafoam, Marvel Mystery Oil, anything?