240D burning oil or leaking? - PeachParts Mercedes-Benz Forum

stephenc03 · #1 12-04-2006, 03:45 PM

I have a 81 240D manual. Recently I fixed what i thought was a major oil leak. I have owned this car for over a year and the entire time I thought the oil leak was coming out of the oil pan. The leak was a rubber o ring that fit on the thrust piece for the oil pump. This thrust piece would spit a very small drop of oil constantly. I had to put a quart of oil every 250 miles! I noticed that some oil comes from the valve cover gasket and the breather hose on top of the valve cover to the intake manifold, but i have no visible oil on the ground, so it isn't that big of a leak. Now I'm putting in a quart every 300-350 miles. I do have some blow by but not enough to push the cap entirely off the valve cover. The blow by that I have just bounces the cap up and down. I cant imagine that my rings are bad becuase it has less than 250,000 miles, I have incredible power, and I can beat any 240D off the line and it is definatly faster than my 300d that has alot more miles on it. How can this car drink so much oil? it also is alot more noisy than other 240's that i have seen. A friend suggested that I have a higher gear ration for the differencial and that is why it is so lowd (thanks pat). I get good fuel economy with 32m/gal@65MPH on the highway. this seems contradictory(sp?). I am just trying to make sence of it all. Thanks
-Stephen

diametricalbenz · #2 12-04-2006, 04:38 PM

It might be a valve stem seal issue.

Does the car have the cyclonic oil separator between the air filter and CCV tube?

Mine burns about 1 quart per 100 miles which is bad and I know it blows a lot of oil out the CCV line because I have an oil separator which fills up dissapointingly fast.

kerry · #3 12-04-2006, 04:48 PM

Good fuel economy could be accounted for by supplementing the diesel fuel with the oil you are losing. If you have the old style vacuum pump, I believe a leak in the diaphragm results in high oil consumption. How is your vacuum? How does an oil pump seal cause an external oil leak?

pj67coll · #4 12-04-2006, 05:10 PM

This is interesting to me as I also have an 81 240D stick. I wonder if our two cars shared the same line? Anyway. I have 200K on a rebuilt motor. My blowby is worse than yours. It will actually blow the cap off. But I'm not using as much oil. I am getting similar mileage though. Averaging 31.5 mpg town and freeway mix. I do blow quite abit of smoke out the back though. Dark grey to black. I think I'll be following this thread as a comparison.

- Peter.

stephenc03 · #5 12-04-2006, 05:33 PM

I pretty sure i dont have one of those

Quote:

Originally Posted by diametricalbenz

It might be a valve stem seal issue.

Does the car have the cyclonic oil separator between the air filter and CCV tube?

Mine burns about 1 quart per 100 miles which is bad and I know it blows a lot of oil out the CCV line because I have an oil separator which fills up dissapointingly fast.

stephenc03 · #6 12-04-2006, 05:40 PM

I understand that I could possibly substitute oil for fuel and that makes sence. I have a vacuum leak in my brake booster but that would possibly consume brake fluid, not engine oil, and it doesn't leak brake fluid. It isn't an oil pump seal it is an o ring that is fitted around the thrust piece that moves up and down on top of the oil pump/vacuum pump. I know that there are two different kinds of thrust pieces and I have the newer kind.

Quote:

Originally Posted by kerry edwards

Good fuel economy could be accounted for by supplementing the diesel fuel with the oil you are losing. If you have the old style vacuum pump, I believe a leak in the diaphragm results in high oil consumption. How is your vacuum? How does an oil pump seal cause an external oil leak?

stephenc03 · #7 12-04-2006, 05:44 PM

Peter,
Other than start up I have no smoke out the back end. The exhuast is surprisingly clean. I dont have grey or black smoke. Your timing might be off. but that doesn't explain why you are getting good gas milage. My friend has a 77 240d manual and he getts about 35MPG and his doesn't burn any oil and is smooth and quite.

Quote:

Originally Posted by pj67coll

This is interesting to me as I also have an 81 240D stick. I wonder if our two cars shared the same line? Anyway. I have 200K on a rebuilt motor. My blowby is worse than yours. It will actually blow the cap off. But I'm not using as much oil. I am getting similar mileage though. Averaging 31.5 mpg town and freeway mix. I do blow quite abit of smoke out the back though. Dark grey to black. I think I'll be following this thread as a comparison.

- Peter.

kerry · #8 12-04-2006, 05:47 PM

Quote:

Originally Posted by stephenc03

I understand that I could possibly substitute oil for fuel and that makes sence. I have a vacuum leak in my brake booster but that would possibly consume brake fluid, not engine oil, and it doesn't leak brake fluid. It isn't an oil pump seal it is an o ring that is fitted around the thrust piece that moves up and down on top of the oil pump/vacuum pump. I know that there are two different kinds of thrust pieces and I have the newer kind.

How do you know it's a problem with the brake booster and not the vacuum pump?

stephenc03 · #9 12-04-2006, 05:53 PM

I thought you read my other post talking about my brake booster. I know I have vacuum becuase my doors still lock intemitenly but one day my car failed to quit when i turned the car off, i knew i had a vacuum leak. I can hear a leak coming from inside the brake booster and especially load with a stethiscope. I thought at first they were coming from the vacuume linse that are near the brake booster but in fact were coming from inside.
-Stephen

leathermang · #10 12-04-2006, 06:52 PM

Quote:

Originally Posted by stephenc03

Other than start up

That is the classic worn valve stem seal symptom. Not much cost for parts but some labor... there is another thread going telling how to do it....

JimSmith · #11 12-04-2006, 07:03 PM

I second Leathermang's assessment. A vacuum pump diaphragm failure is dramatic, especially at idle. Copious quantities of thick white clouds of smoke, enough to hide the car entirely in broad daylight. Very small failures also make it apparent as the translucent white, about 3/8" dia tube from the pump to the intake manifold turns black.

Valve seals in a Diesel are not generally a big liability until they are really shot. Intake vacuum is typically pretty mild, except at idle, so you should have a telltale puff from the tailpipe if you let it idle for a few minutes. Jim

stephenc03 · #12 12-04-2006, 07:54 PM

So you guys think that my valve guide seals are bad. That would allow oil to be sucked or drip into the combustion chamber and that is where I am loosing oil. If this is the case why am i not able to see gray or black smoke out the back. Burning one gallon of oil per 1000 miles is alot of oil to not see anything but normal exhuast come out the back isn't it? I know something is leaking some where i just don't know specificaly. For a while, I know this isn't correct, I was running 30weight oil becuase I was loosing so much so often and the 40 weight is so expensive. After switching back to the straight 40 weight i noticed a difference in oil consumpsion becuase obviously the oil is thicker and seal better. Thanks guys
-Stephen

Quote:

Originally Posted by JimSmith

I second Leathermang's assessment. A vacuum pump diaphragm failure is dramatic, especially at idle. Copious quantities of thick white clouds of smoke, enough to hide the car entirely in broad daylight. Very small failures also make it apparent as the translucent white, about 3/8" dia tube from the pump to the intake manifold turns black.

Valve seals in a Diesel are not generally a big liability until they are really shot. Intake vacuum is typically pretty mild, except at idle, so you should have a telltale puff from the tailpipe if you let it idle for a few minutes. Jim

leathermang · #13 12-04-2006, 08:33 PM

Quote:

Originally Posted by stephenc03

So you guys think that my valve guide seals are bad. That would allow oil to be sucked or drip into the combustion chamber and that is where I am loosing oil. If this is the case why am i not able to see gray or black smoke out the back. Burning one gallon of oil per 1000 miles is alot of oil to not see anything but normal exhuast come out the back isn't it?
-Stephen

I think your valve stem seals are bad from your description of smoke at startup.... but that does not preclude ALSO having leaks ... my car was that way.... the PO had a copper washer on the oil plug with dings... lost lots of oil from there... valve cover also leaks... and I need valve stem seals... but when warmed up you can't see the oil in the rear view mirror... but it is going away....It was using a quart per 300 miles...
ALSO... there is much discussion in the archives about what level you keep your oil at... and the possibility that someone put the wrong dipstick into your engine... my oil useage went WAY down when I stopped keeping the oil at the max mark and started keeping it half way between that and the low mark...

stephenc03 · #14 12-04-2006, 09:06 PM

I never thought that my dipstick could possibly be the problem. Is there a part number on the stick to match to a known number for that model? When I say smoke at start up I mean very little. my back windows are tinted and when i look out the back window i cant even see it but if i look out my driverside window i will see a little puff of smoke. I just assum that is becuase i am starting it up and it is cold with the pedal down to the floor, i'm not concerned at all about that. What would explain the lowd engine noise, is it coming from the seals? Also I have always put two full gallons of oil whenever I change my oil. How much oil do the engine specs say to put in?
-Stephen

Rmcfarland · #15 12-04-2006, 09:12 PM

Interested to follow. I have a '79 240d that has oil all over the engine, but does not drip, so my leak cannot be too bad. My blowby will bounce the cap around but not blow it off. I burn a quart of 15w40 every ~600 miles or so. Interested to hear more, I hate burning oil.

I did read in a thread that the oil return line from the air filter housing can get clogged. Mine may be, I see lots of oil there. Going to look at it when it's not so danged cold.