Smoke - PeachParts Mercedes-Benz Forum

mcamara · #1 01-05-2005, 12:05 PM

Hi again,

I posted a few months back with an '83 300SD problem. Been away from the forums for awhile. Got caught up in the paintball forums.

Anyway, I had problems with white smoke in my last post. Short version is that the mechanic said I had some blowby that could be caused by gunk in the rings due to my city driving. He disconnected the breather tube from the valve cover to the air filter and suggested that I drive it in 3rd to keep the rpm's up (45mph is the typical speed limit of my commute) and drive the heck out of it. He also put another tube on the valve cover and routed it down along the engine.

Everything was great for a few months but now I get these great plumes of white smoke in stop and go traffic and when I take off from a stop. This doesn't happen every time but at least every third time. I got stuck in traffic last night and it was smoking so bad I had it towed because it was becoming a hazard. If I get up to 45 or so, it appears to dissipate but then it may start to smoke and envelope me in a cloud at the next red light.

He had also suggested STP oil treatment. I used it a few months ago and it helped a little I was happy without it. I added some more when this problem started and it made the car smoke even worse. What does this sound like?

I also have problems with the vacuum cutoff. I have to shut the car off under the hood. Could this be related?

Thanks in advance. Sorry for the long post.

Pete Burton · #2 01-05-2005, 12:27 PM

Sounds more like smoke caused by dirty injectors and/or injector timing off. Smoke can also be caused by a head or headgasket problem but with your engine (the 617) the chances are pretty remote. I would get the injectors checked/corrected, have the valves and injection timing checked/corrected and put the breather back where it belongs. Try a good FUEL additive as you probably aren't putting a lot of miles on any way. Lastly, give it an italian tuneup!

mcamara · #3 01-05-2005, 12:52 PM

I had the injectors replaced and valves adjusted last winter. (HARD starting).
Would they cause white smoke that smells like burning oil? This is much like the symptom I took it in for.

When the tube was removed, vapor was chugging out of it. It's the 2 piece type so it would actually pop off by itself every couple of days. I've been thinking about putting it back on to see how it behaves now.

I'm also very curious what the STP oil treatment is doing that is making it worse now. It had no ill effects the last time I used it. Now I have to change the oil to get it to settle down if I add the stuff.

Pete Burton · #4 01-05-2005, 01:13 PM

Quote:

Originally Posted by mcamara

I had the injectors replaced and valves adjusted last winter. (HARD starting).
Would they cause white smoke that smells like burning oil? This is much like the symptom I took it in for.

sure could. You said injectors "replaced". Problem is, many here have reported terrible quality problems with "new" or "rebuilt" injectors. Bosch has completely dropped the ball on responsibility for specs on the nozzle portion of the injectors. "replaced" could mean almost anything with regard to quality unfortunately, and it's highly possible that the injectors are a big part of the problem. IMHO, the best way to deal with it is have injectors checked for spray pattern, atomization and pop pressure. All injectors in a set should "pop" within a total range of 5 bar, and 3 would be even better.

If the valves were adjusted properly, that's good. But the valve timing and injector timing matters too. Use the search and you will find a lot of great info from members who have posted a lot of "how to" info here, which is useful if you do it yourself, or pay someone else to do it (correctly).

mcamara · #5 01-05-2005, 01:23 PM

Thanks. That's encouraging. I have about a half a can of Diesel Purge left. I'll put it in the fuel filter and see if that helps.

The mechanic seems to know his stuff. He's been working on these since he was a kid in his stepdad's shop. He's an advocate of the Italian tuneup as well. When I had the last problem he asked how many miles were on the car and I told him 200k. He said "Okay, so she's low mileage".

JimmyL · #6 01-05-2005, 02:54 PM

I have almost the exact same problem. I had injectors rebuilt and had no change. I don't have blowby from the oil filler or dipstick, though. Taking it to an indy in a week or so, and will post at that time.
It smokes horribly at idle and coasting. Not much at all under acceleration or high rpm situations. Misses at idle and also has no power. Non-turbo.
We'll see soon.
JL

mcamara · #7 01-05-2005, 09:15 PM

Good luck and keep us posted.

JimSmith · #8 01-05-2005, 10:28 PM

mcamara,

Where is the white smoke coming from, the exhaust pipe or the new crankcase vent line your mechanic put in for you? What is your typical oil consumption rate? Has it changed since the rerouting of the crankcase vent?

If the smoke is coming from the exhaust pipe, the mechanisms causing the smoking may be different than if it is coming from the crankcase vent. Jim

mcamara · #9 01-05-2005, 11:11 PM

The clouds are coming from the exhaust. There is a bit of smoke coming from the "vent" but that has not gotten worse. May be better. Oil consumption decreased drastically since the venting. Less leakage. I'm not trying to blame the mechanic. I'm just trying to be thorough in my description. Not sure if I made that clear.
Everything was great for about 6 months or more except for the smoke from under the hood. Now it's billowing out the exhaust. Not constantly but very frequently. That's what has me stymied.

The Diesel Purge didn't help but I guess it's not going to fix a bad injector.

JimSmith · #10 01-06-2005, 07:01 AM

These cars are equipped with a vacuum pump because they do not produce vacuum like a gasser does under normal operating conditions, and the brakes, locks, air conditioning, fuel shut off valve and automatic transmission among other items use vacuum for assist, control and as the primary force for actuating valves or mechanisms. On the older models (220D and 240D, and possibly early 300D) the vacuum pump used to vent to the intake manifold through a hard, plastic tube that ran across the front of the engine from the pump to the air intake system. When the pump diaphragm cracks or leaks, it gets oil on the wrong side of the pump, making engine oil available to the intake/air cleaner. Under normal operating conditions there really is no vacuum in the intake manifold or air cleaner, so there is little to draw the oil into the intake. The throttle controls on the older 616 (240D) engines include a feature that throttles the intake slightly, creating a vacuum. I have had the diaphragm fail and end up pumping/sucking loads of engine oil into the intake manifold, leading to huge clouds of very thick white smoke at idle. It diminishes at any load where the intake vacuum decreases. Very alarming. I am not sure if the vacuum pump on your car vents to the intake or has an internal vent to the crankcase. But it sounds like your problem is similar enough, I would look for ways your engine is letting you suck engine oil into the intake. Jim

TonyFromWestOz · #11 01-06-2005, 07:41 AM

White smoke in diesels in unburned fuel - this includes unburned engine oil.

1. Blow-by gases in the inlet manifold are burned with the fuel - the exhaust will not smell of "burnt oil" from blow-by gases. I regularly burn 50% used engine oil in my OM617 without any "burnt oil" smell.

2. The most likely way unburned oil (odour/smoke) will occur from the exhaust of an OM617 is either from the turbo, or from the exhaust valve guides, or from oil being injected into the exhaust (a la "smoker" modification).

3. If your engine starts easily in cold weather, you do not have compression issues, and are unlikely to have MAJOR blowby or excessive oil film on cylinder walls.

You should restore the crankcase vent to the air cleaner.
Check for any oil leak into the exhaust (PO has a "smoker" installed?)
Have the valve guides and seals checked/replaced.

I may have missed something, if so, others will pick up on them.

Regards,
Tony

mcamara · #12 01-06-2005, 07:48 AM

Jim- It has sucked oil into the dash lines.

Tony- It starts fine when the weather is in the 20's. So that's good news.

Thanks for your help. Will investigate further tonight.

Pete Burton · #13 01-06-2005, 08:50 AM

Your symptoms could also be explained by excessive blowby. Hopefully, that is not the case. It would probably be worth the effort to determine roughly how much blowby is occurring past the valves and rings. A valve adjustment can't hurt, as well as a compression check. If you pull the injectors to test and do the compression check, perhaps you can get some penetrant through the prechambers to soak into the rings. Make sure you crank it over good afterward by hand before you put the injectors back as you don't want any puddle of liquid in there when it's closed. A fairly worn engine with a lot of blowby will still start well in the 20's, use an increasing amount of oil, and smoke badly at times. This was just how my car ran before I pulled the engine at 300K and put in a rebuild. Again, with 200K, I would look long and hard at everything before making such a committment. Chances are you won't need to.

ps. Your engine has a piston type vacuum pump.

mcamara · #14 01-06-2005, 12:07 PM

Thanks folks.
Pete- what is the significance of the piston type vacuum pump? Could the fact that my dash vacuum lines are full of oil be related to this problem or are you saying that they're unrelated?