Greetings all,

I am seeking some assistance in diagnosing the problems that have unfolded in my beloved vehicle.

Brief history:
2 years ago engine was reconditioned - rebored, new pistons. Past 2 years it has been running great. No oil loss internal or external and no coolant loss.

Current symptoms:
Over past few weeks I have noticed smell of burnt oil after getting out of car. Losing oil at rate of about half a litre or more a week. When driving on flat or up hills engine performs well with little smoke, but after decelerating down hills under brakes car then idles very poorly, then on acceleration black and white smoke blows from exhaust, this is coupled with a pinging sound from the engine area or under the car. After accelerating for a few seconds it seems to clear.

Don't seem to be losing any coolant. Oil on the dipstick seems normal colour.

Not sure if this relates or a separate issue, but I have also lost vacuum or booster to my brakes over the past week or so also. Applying the brakes is like a gym workout.

What I am thinking:
It can't be a headgasket because engine performs fine under load.
Could it be the fuel Pump -?
It seems to be overfueling when the nose of the car is facing down but why??

Any enlightened help would be greatly appreciated.

Many thanks.

Regards,

Jason

This year of the car has a vent line from the vaccum pump to the engine. . I think the diaphram has failed in your pump and oil is being taken in instead of the air. That vent line should have no oil in it. I think you get off pretty cheap this time.
That is probably why you have lost vacuum as well for your brakes etc. Not a bad fix really if so as the kit is not too expensive for your pump. The principal partial proof is the change experienced when going downhill as those vacuum pumps seem to get and feed more oil somehow. Thats when the front of the engine is lower.
Do not procastinate fixing this if it is the problem as I do not know if you could get enough oil from that source for your engine to runaway. There have been reports of actual acceleration going downhill. Probably depends on the amount of leakage of the diaphram in your older designed vacuum pump.
You could remove that vent line. Run engine and see if it clears up after burning any remaining oil out from the leak if there. Then you have positive proof if uncertain. The engine should restore itself to normal with the vent tube disconnected. Still gotta rebuild the pump though if so.
Welcome to the site by the way and let us know how it goes. As an afterthought your design of vacuum pump plumbing was changed to eliminate this posibility occuring not many years later. Also a newer design of piston vacuum pump was installed eventually. In my opinion there is nothing really wrong with the pumps design in your car. It is a rubber diaphram type. Read the archives on this site for any other questions that relate to your problem. Also will be tutorials on how to rebuild the vacuum pump I think. Not a bad job really for a new member..
When you determine it is the problem try to support the sites sponsers. They have an excellent reputation, fast delivery of parts, friendly, just credible people to deal with. Look up their kit on site for your pump.

Thank you so much.

After I investigate I will update this thread with the outcome.

Kind regards.

Jason

Barry's right on the money. You have a failed diaphragm in the vacuum pump. The diaphragm and check valves can be replaced using a rebuild kit while leaving the main body of the pump on the block and just removing the cover. No need to remove radiator but I think I did remove the fan shroud to get access. I did mine in less than an hour and a half in the dead of winter.

__________________
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

I did as Barry suggested and disconnected the vent tube running from the vacuum pump to the intake manifold area - and guess what - it was dripping with my engine oil.

The engine oil was being sucked up through the vacuum pump and into the cylinders - well I never would have guessed - thank you so much for your mechanical wisdom - it has given me enormous relief.

I didn't blow any smoke at all today.

Now I just need to order a rebuild kit for my vacuum pump - then I will get my brake booster back on line and my central locking system may even start working again -

It's amazing how one failed diaphram can have such diverse and extreme effects on the running of the vehicle.

I will report back when I have the vacuum pump working again.

Cheers till then.

Jason

I opened up the vacuum pump and replaced the faulty diaphragm. Now the car is again running smoothly, smoke free and my brakes are back on line. I was so used to pushing hard on the brakes that it took me a few minutes to get used to the amazing responsiveness of the brakes.

The was a rip/tear in the rubber diaphragm.

Just a little added point that I discovered while picking up my parts at my local Merc parts dealership. I asked the guy if he had any fuel line that ran as a return line running between the injectors and back to the fuel filter. He didn't have any but he told me where I could get some. He directed me to a vintage VW dealer. The line is used as a vacuum line in the earlier VWs. The line is identical in diameter and make up - complete with braided exterior - the only difference was the colour - bright orange instead of the usual creamy/grey.

Thank you for your help Barry and Kerry, much appreciated.

Jason

The VW dealer also should have Diesel retun hose/line as the older VW Rabbit diesels as the Bosch injector bodies are the same as Mercedes. I used VW rabbit injector bodies with Monark (for Mercedes) spray nozzles to assemble the injectors that are in my 300D right now.

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84 300D, 82 Volvo 244Gl Diesel