Hi guys,

I'm helping a buddy with a 1979 240D. When it has been sitting for any length of time, it has a really smoky start. It will continue to smoke until it it warmed up, at which point the smoke is very minimal. I am assuming this is likely valve stem seals, and I'm going to try and help him swap them out (it's affordable and apparently not too hard). Does this sound like a reasonable diagnosis/cure?

It does have some blow-by, and he purchased a compression tester, so we're going to pull the glows and try and check the compression, probably after we change the valve stem seals, and adjust the valves.

I helped him with a MMO piston soak and a diesel fuel system purge (using Sea Foam) and pretty much eliminated the BLACK smoke (which said to me his injectors were fouled), so the smoky starts are all from oil - the smoke is bluish white, and it certainly smells like burning oil, not diesel.

I've told him that it's possible that the blow-by is either from sticky rings, or from carbon/varnish build-up on the cylinder walls (it has under 200K miles) or perhaps the PO didn't change the oil enough, and it's just plain worn. I told him to "just drive it" if we can fix the smoky start.

(EDIT: I now suspect that the car has been run on WVO, as there is evidence of a heat exchanger installed in the engine bay - see the photo in post #12. It is certainly not stock, and I can't think of any reason why one would want to heat up the diesel fuel around here in the Pacific NW. It's likely some hippy fed it a diet of WVO or SVO. If so, then I am also considering how we could remedy the damage that has been done - possibly from stuck rings? Or carboned-up cylinder walls? I even suspect that the car has more miles than are indicated by the Odo, as the manual transmission certainly has more 'I'm worn' noise to it than my 83.)

Don't know what his oil consumption is.

His vehicle has less power than my 83, but I also know that the 83s have a few extra horses. His is a 79 MY.

Any hints, tips, or advice is welcomed!

Thanks,

PE

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83 240D - 4 speed manual - Manilla Beige
189K miles, Tachometer mod, cool wooden shift knob from PeachParts, CocoMats, Original factory paint, manual windows, manual sunroof. Starting to add AudioWrap to this car too!

valve stem guides? you need to take the head off to do that. I think you mean the valve stem seals. Try it, can't hurt. However I have not had it help any engine I tryed it on. Always ended up being rings. If the car has not been run on the highway much it may just be carboned up. Italian tuneup will help this. However I found it takes quite a few highway miles to clean up. My Dodge pickup(with cummins) smoked a lot on startup. It took nearly 10,000 miles of trailer pulling , and highway miles to finally start without smoke. Oil usage went down too. Now a reasonable quart every 2000 miles.

A compression test will tell a lot.

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1977 240D turbo

79 has a diaphragm vacuum pump I believe. It could be a failed diaphragm on the pump sucking oil into the engine.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

That should be easily noticed: black air line to the air filter housing, constant smoking, even with a warm engine, no brake booster.

I changed the valve stem seals on my 200D and the rotocaps and valve springs, but there is no real change in the smokyness of the engine.

Smoke when the engine is cold, is usually unburnt diesel, because the engine is too cold.

THanks for the diagnostic tip! That makes sense.

The smoke I am seeing is mostly when cold. The smoke is white and sometimes bluish. It is not black. If you take the car on the freeway for 10 minutes, then the smoke is pretty much completely gone. If you do see any, it is bluish white. That's what is making me think it is the valve stem seals.

I own several diesels, and I know black diesel smoke when I see it.

Anyone have experience with having a smoky start and having it go away after replacing valve stem seals?

Thanks,

PE

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83 240D - 4 speed manual - Manilla Beige
189K miles, Tachometer mod, cool wooden shift knob from PeachParts, CocoMats, Original factory paint, manual windows, manual sunroof. Starting to add AudioWrap to this car too!

When the temperature of the engine is low, unburnt diesel is white. Also diesel will condensate on cold parts of the engine and not combust.

Then there is condensation which has formed in the engine and in the exhaust to consider too, that will create white smoke.

Ah, very good point.

Sincerely,

PE

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83 240D - 4 speed manual - Manilla Beige
189K miles, Tachometer mod, cool wooden shift knob from PeachParts, CocoMats, Original factory paint, manual windows, manual sunroof. Starting to add AudioWrap to this car too!

smell the exhaust, burnt oil smells very differant then unburnt diesel. unburnt diesel will sting your eyes.

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1977 240D turbo

Snif Snif... It's definitely OIL.

-PE

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83 240D - 4 speed manual - Manilla Beige
189K miles, Tachometer mod, cool wooden shift knob from PeachParts, CocoMats, Original factory paint, manual windows, manual sunroof. Starting to add AudioWrap to this car too!

Valve seals may or not help. Unlike mercedes gas engines of old they do not seem to be as critical.

Some have reported improvement as well. So in general it is a crap shoot in my opinion. The good is that it is a cheap one.

Also have your friend try running with the oil level about halfway between the marks on the dipstick. Some like to consume more oil when they are filled to the top mark. Make sure the correct color code dipstick is present as well.

Is there any indication of waste vegatable oil usage on that car?

I've spent a lot of time and money trying to eliminate smoke problems on my W115.

1. New injectors (PO).
2. Valve adjustment (for compression check).
3. New filters/lines and quality fuel with a cetane additive.
4. Diesel purge (sounded like a new engine while on The Juice).
4. Adjust the timing of the injection pump (not too far out).
5. New timing chain (significant stretch).
6. Finally, rebuilt the injection pump (needed sooner rather than later).

There were changes in the smoke output at each stage...sometimes for the worse!

After all that, guess what? I still have some white smoke on start up and at warm idle on cold days. It's much less than before, but not totally eliminated.

I plan on getting the valve seals replaced and the vacuum pump rebuilt, though. I have no indication that any are bad at present (although they can contribute to smoking issues). They'll be replaced just for prevention's sake.

Just like The Bomb, I've learned to live with it. :shrug: Some smoking is just to be expected at this stage in our cars' lives. That doesn't mean you don't have an addressable issue, but that eventually you could be taking on a fool's errand.

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1974 240D "Boldie" 170K.- New timing chain/freshly rebuilt IP/replaced valve seals/injectors/upgraded stereo/new Bilsteins with Yokohamas/fresh paint and rocker panels plus lots of welds.

Hmmm. That's a good question! I went out and looked at the car. AHA! What do you guys make of this? It looks like a heat-exchanger that has been plumbed in-between the fuel tank and the heater hoses! Certainly my 1983 240D doesn't have anything that looks like that... From what I can see, it appears to be a set of copper tubes with the heater hoses hooked up to it, and a copper coil running in a helix around the copper tubing. The whole thing is wrapped up in some kind of foam insulation! (See the picture)

I have got to assume that this was to heat the fuel as it comes from the tank, and I also assume that this is for SVO/WVO use. What do you think?

If this is the case, then I would think it stands to reason that his significant blow-by and and smoky startup might be caused by excess carbon and varnish in the cylinders caused by WVO use?

OK, if this IS the case, then what is the cure for all this?

Thanks,

PE

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83 240D - 4 speed manual - Manilla Beige
189K miles, Tachometer mod, cool wooden shift knob from PeachParts, CocoMats, Original factory paint, manual windows, manual sunroof. Starting to add AudioWrap to this car too!

Depends on if there is scoring damage or just coked rings. Soaking the cylinders down for a week with marvel miracle oil and the block heater on might help. Chemical action is always better and faster at reasonable temperatures. Below about 70 degrees it can be almost inert.

I do not suspect scoring damage as the problem clears off or reduces as the pistons expand. I doubt there is any option to the soaking down first from what you post.

As it does sound like some of the rings may be glued into their fixed position or so sticky with gunk they cannot respond fast enough to seal well.

Also running for awhile after the soak down with a quart of marvel oil in the crankcase and one in the fuel tank may help as well. Diesel fuel does not seem to cut wvo residues. The mystery oil solvent base seems to. Fairly inexpensive to buy and add a little more to each cylinder once a day. Remember to roll the engine over well before innstalling the gllow plugs or injectors so you do not get a hydro lock.