71' 220d Rough idle blue smoke, black/brown smoke when accelerating - PeachParts Mercedes-Benz Forum

CvdH · #1 01-30-2011, 07:05 PM

Hi, I have a 1971 Mercedes 220D with 150,XXX miles on the original engine that has been acting up lately. It was running kind of rough at idle with white smoke a few weeks ago, so I decided to go ahead and install some new Bosch injectors. After I did so, the problem did not go away. It has gotten progressively worse. It now smokes blue smoke at idle and idles really rough, like it's missing a cylinder. When I accelerate black/brown smoke billows from the exhaust for the first few seconds and then black smoke continues to flow until I get up to 50/60mph. It consumes oil at an alarming rate, about 2 quarts in 30-50 miles. It seems to idle better when cold and get worse as it get hot. When just cruising, it drives fine, occasionally however, when driving at highway speeds, it makes a knocking sound and brown smoke pours out the back until the knocking goes away, usually about 3 seconds. I did a compression test today and all cylinders tested over 300 (the highest my meter goes) and got there within 3-4 cranks. The level of compression stayed constant after cranking stopped and I did not hear any leaks. All glow plugs looked good, had a thin layer of dry black soot. I recently (within the last 500 miles) changed the oil, adjusted the valves, changed fuel filters and fuel lines. I am at a loss for what to do next... Any help would be appreciated!

kerry · #2 01-30-2011, 07:07 PM

Does the engine have a vacuum pump that vents into the intake manifold? If so, my hypothesis is that the vacuum pump diaphragm has failed.

CvdH · #3 01-30-2011, 07:19 PM

Quote:

Originally Posted by kerry

Does the engine have a vacuum pump that vents into the intake manifold? If so, my hypothesis is that the vacuum pump diaphragm has failed.

Yes, I believe it does, I have noticed recently that (What I assume to be the vacuum lines) have air bubbles in them and nothing is moving. I have put up a picture with arrows pointing to what I am guessing is are the vacuum lines.

kerry · #4 01-30-2011, 07:26 PM

I can't tell from the picture but if you look inside that 'clear' vacuum line that goes over to the intake manifold, I'll bet you'll find oil in it as a result of the vacuum pump diaphragm failing.

CvdH · #5 01-30-2011, 07:36 PM

There is oil at the base of the clear line, and oil residue throughout. There is also oil residue/ staining at the connection where the line meets the intake. Would replacing the vacuum pump diaphragm be a relatively easy and cheap fix?

kerry · #6 01-30-2011, 07:49 PM

I'm not familiar with the vacuum pump on a 115 engine but on early 617's with intake vented vacuum pumps, the repair takes a little over an hour, is not difficult and the rebuild kit available at 'Buy Parts' at the top of this page is pretty inexpensive.
There quite a few threads on here on rebuilding the vacuum pump if you search. Make sure you're looking at diaphragm pump threads and not piston pump threads.

Biodiesel300TD · #7 01-30-2011, 07:52 PM

I've done it on my 123 240D with the pump still in the car.

Palangi · #8 01-30-2011, 07:57 PM

A 220D also has a diaphram in the injection pump. When it fails, you get smoke. I don't remember the details, but if you search on the word diaphram, you should be able to find it.

Diesel911 · #9 01-30-2011, 08:01 PM

It looks like there is a couple of kits available for the Vacuum Pump. At the place I looked the kit with only the diaphragm is $12 and the kit with check valves is $16.

Clearly an inexpensive fix.

The Diapragm in the Fuel Injection Pump (it is the Governor) is around $265 each if you can find one. And, if you replace it you need to be very careful where the shims go so you can put them back in the same place on the new Diaphragm. I would save that for last.

Your Engine does not have very many miles on it but it could be the 40 year old Valve Stem Seals are no good. Since this particular Engine actually has some Intake Manifold Vacuum Due to the Butterfly Valve used to create Vacuum; that could cause Oil to be sucked past bad Valve Stem Seals.

CvdH · #10 01-30-2011, 09:22 PM

Thanks for the replies guys! I really appreciate it. I will start out with the simplest and least expensive thing first, and replace the vacuum pump diaphragm and see how she goes from there. I'll order the parts tonight and hopefully get them in by the end of the week and get my car back on the road. I'll keep you informed! Thanks!

kerry · #11 01-30-2011, 09:26 PM

You could test the engine by unhooking the clear vacuum line going to the manifold and putting the manifold end in a jug, plugging the hole in the intake manifold and driving around. If the problem goes away, you'll know it's the vacuum pump diaphragm. The line is probably brittle and might break.

Zeppo2K2 · #12 01-31-2011, 12:51 AM

I changed the diaphragm in my 220D in about 2 hours. It was not cracked, but oil was leaking out the bottom of the pump housing seal, which is made via that diaphragm.

It has been suggested that the bearings be changed at the same time, as if they come apart, they will probably end up in the chain galley and make a big mess of the engine.

Check to make sure you have no vacuum leaks after the repair is done. I do this by pulling a hose after a day of no use, and listen for the rush of air. If there's no leak, the pump works much less (the diaphragm holds the roller away from the drive cam). I figure the bearings really wear on a pump thats been worked a lot. Ron

CvdH · #13 01-31-2011, 01:23 AM

Kerry - I just went out and did this, and what a difference it made! From this - my car spewing smoke, engine rocking back and fourth and relentlessly sputtering to this - a perfectly smooth, smoke free, sputter free idle. It was beautiful! When I started the engine I payed attention to the vacuum line and could immediately see the small amount of oil that was at the bottom of the vacuum line begin to creep up. As the car got warm it reached the top of the line and flowed into the jug. The higher the rpm, the faster the flow. This explains why it ran good in the beginning, but very poorly after it warmed up a bit; also why it was better at very low idle. I will be ordering the diaphragm first thing in the morning.

Ron - Thanks for the tip! I will definitely replace the bearing while I'm in the vacuum pump. The last thing I want is any more problems in the future that could have been easily avoided. Do you remember where you bought your bearings from? I tried a quick google search, but turned up nothing.

After about 4 weeks of troubleshooting, finally figuring it out feels really good! I went through everything I could think of, but I never thought of this, and probably never would have without your guys' help. At least I got to know my engine a little better in the process of all this troubleshooting.

kerry · #14 01-31-2011, 12:05 PM

It's possible the bearing problems with the vac pump apply to piston pumps and not diaphragm pumps. I'm not sure about that but I would check into it before searching for a bearing for your diaphragm pump.