I have a 91 350 sdl that smokes when cold at idle and has an idle knock. It runs quiet and smooth above 1500, and has 137,000 miles. After reading several posts I came to the conclusion that I will send the injectors to a shop in San Diego that can rebuild and balance them to within one bar. As I pulled off the turbo outlet tube that goes across the rocker cover I was a little surprised at the soot in the tube after the EGR. I read in a post last nite that said to put a bb in the vac hose to the EGR to eliminate hot gases that could help form little carbon balls that could enter the combustion chamber and bend a rod. I also spoke to a tech in Fl. that said the reason that the rods would bend was due to glow plug failure and the piston having a hydro locking condition when cold starting ??? Anyway is the soot normal, or do I have a turbo oil leak into the outlet side of the compressor or ???? Thanks for all answers as I am trying to stay on the right track with this engine.

Soot is normal, but a thick layer of glassy carbon and soot is trouble. If it just wipes off, don't worry (it will not "coke" in place and make the crusy mess if you use synthetic oil). If you have a crusty buildup that won't wipe off, take the intake off and clean it out, and you may want to clean the intake ports as well (vacuum up any loose stuff when you are done). Likely it won't be too bad if you change the oil often and use synthetic.

Hard knock isolated to one or two cylinders that goes away above 1500 rpm could be leaking pressure valve seals, but you don't get much if any smoke then.

You should also check valve timing (aka chain stretch) and injection timing. These engines are not known for chain wear, but I'd check anyway, as late timing will also give you smoke, knock, and rough running at low rpm.

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!

PSFRED, thanks for the info. It only seems to smoke at idle until I get her warmed up. I used a long 3/8 extension to listen to each injector, and # 4 is where the idle knock comes from, without dought as the other injectors have a slight rap to them when running, so I hope that a quality rebuild on them will make the knock go away. I also ordered the compression gauge adapter from Snap-On, but I do not know what compression numbers to be looking for ? When you say valve sels leaking, do you mean the items at the top of the IP where the lines connect to the injectors. Last thing is, Oil, I was going to go with 15-50 Mobil one as I have an account with the Mobil dist. and where do we get aftermarket gaskets. Thanks for your time.

PSFRED, I also have oil leaking at the gasket where the crossover tube connects to the plenum, and when you look down into the turbo past the EGR it looks a little wet, clean with no soot, but above the EGR is where the soot begins, so turning off the EGR makes sense.

The gasket leak is normal, as is a slight ooze at the bottom of the intake runners (although that usually turns into a leak, meaning time to replace the gasket). You can put in a new gasket, should fix it for the time being, but they usually show some black oil there.

Oil in the turbo is normal -- the blowby is routed to the intake in front of the turbo, and ALL diesels have some at highways speed.

Mobil 15W-50 is fine, it's what I use when I can find it. These days, it's Mobil 1 Truck and SUV oil (aka Delvac 1) which is probably better, since it has better compression engine ratings and holds more soot.

If the engine has been run on dino oil up to now, change the oil filter and top up the oil at about 1000 miles -- all the varnish in the engine will dissolve and any hard stuff will end up in the filter, sometimes plugging it. Won't be a problem with good maintenance, but filters are cheap and the job is easy.

The pressure valve holder is what the injection lines screw into on the IP, but I'd have the injectors checked first. They do usually run 250,000 miles or more without problems, though.

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!

Compression spec is 26-32 bar (377-464 psi), 18 bar (261 psi) min, max 3 bar (43 psi) difference between cylinders. I hope you weren't planning to use a 300 psi gasser compression tester.

Sixto
95 S420
87 300SDL