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Old 01-22-2002, 09:37 PM
Posts: n/a
question regarding oil usage

Hello all!

Well, I've had the 240D (my first MB) for 2 1/2 months now (I am third owner) and have gone through and fixed a bunch of things. The list of things I want to do (about 15 things now) is not too bad and most can wait till I find the time/money.

Anyway, I fixed my one and only oil leak (from the oil filter housing gasket) but my car still drinks oil. The car has 242,000 miles on it and the engine has never been rebuilt. I am trying to narrow down the cause of the oil I will give you as much info about how the car acts/drives as I can to help with the diagnosis.

The car starts just like my Honda (always within a second from when I first turn the key to "start"). I did have to replace the glow plugs as one was bad when I bought the car...but even then, the car started right up. I don't even notice a difference when it is freezing outside (in the 20s).

The car does not smoke upon first starting it up, at idle, or under heavy throttle or load. I have even asked a friend who was once following behind me on the highway if the car "smoked" and he said that it didn't.

The car has plenty of least compared to the other 240Ds I was testing out before I came across this one. I have heard many people on this forum complain about the power of the 240D, but mine isn't bad. Sure, it isn't a rocket, but it is ok...if you know what I mean.

The engine runs/idles very good and I don't have any knock or irregular running from the engine upon first starting it up cold. I guess you could say that it isn't a "cold-natured" diesel.

So here is my big concern: The car uses 1 qt of oil every 450-500 miles. I have simplified life by just adding 1/2 to 2/3 quart every time I go to fill the tank.

If the engine ran like crap, smoked, had no power, or was hard to start, I would consider a rebuild right away. But, as I already stated, the engine runs great.

Given the information at hand, I would appreciate any advice as to how to proceed on this. I really don't want to mess with the engine right now as it runs too good to tear it down.

BTW--I have not done a compression test. I know it would be key information in helping to diagnose the problem....but haven't done it. Not even sure if I really need to since it runs so well.

Thanks for the help and I look forward to reading your comments.


Last edited by mrwith; 01-22-2002 at 09:44 PM.
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Old 01-22-2002, 09:40 PM
Registered User
Join Date: May 2001
Location: Michigan
Posts: 1,373
My Volvo diesel uses about the same. However, I have all the compression signs (smoke, hard starts, etc.).

If you don't find my side issues, I'd just throw the oil in and be happy.

'84 300DT 298k (Aubrey's)
'99.5 Jetta TDI IV 251k (Julie's)
'97 Jetta TDI 127k (Amber's)
'97 Jetta TDI 186k (Matt's)
'96 Passat TDI 237k (Don's
'84 300D 211k Mint (Arne- Undergoing Greasecar Conversion)

'82 240D 229k (Matt's - Converted-300DT w/ 4 speed
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Old 01-22-2002, 10:13 PM
Posts: n/a
Adjusting the valves is the 1st thing next on my "to-do" list. I don't have the equipment to do it (I hear that a person should have a couple of bent 14 mil wrenches at hand). I guess I could take a couple of regular 14 mil wrenches and heat them up and bend them....but sometimes when you do something like that (depending upon the type of cheap material they used to make them) you could loose the temper in the wrenches and they wouldn't hold up well. Has anyone tried this with success? I am still looking at ebay for a cheap set to bid on.

As far as checking the compression....I don't have the equipment. There is a local independent guy I could take it to. But, I really would rather spend the money on buying the equipment to do it myself instead of paying him to do it. What exactly do I need to check compression?

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Old 01-23-2002, 02:33 PM
Posts: n/a
We have the same car, a 1980 240D. And they sound an awfully similiar. My car does not use as much oil as yours, about one quart every 1200 miles, but it does smoke. It generally does not smoke when started, but when at a stoplight it can be enbarrassing. Otherwise the car runs flawless.

My next item on my to do list is the adjusting the valves. Let me know if that makes any difference for you.
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Old 01-23-2002, 02:43 PM
Registered User
Join Date: Jun 2000
Location: Saugus, CA USA
Posts: 2,035
A well running diesel could run on motor oil and not smoke. Your ONLY problem is where the oil is comming from, maybe, it might be ok.

Check your crank vent, it could be sucking oil that way. It could also be the valve guides and/or seals.
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Old 01-23-2002, 02:50 PM
jcd jcd is offline
village idiot
Join Date: Jun 2001
Location: Northern New Jersey
Posts: 1,102
Mine too

I have a 1977 300D, 177,000 miles. Mine uses oil at the same rate. I have a small leak at the oil filter housing as well, but not enought to account for the amount of oil I need to add.

Otherwise, the car starts great, runs like a top and I am following diesel don's advice, add the oil and keep smiling, and adjust the valves in the spring.

PS..any tips on replacing the oil filter housing gasket. If I get a warm day, I am going to take it on.

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Old 01-23-2002, 08:57 PM
Posts: n/a

When I replaced the oil filter housing gasket I also had to replace the gasket (on the housing) where the oil pressure line connects to the housing. So I really replaced two gaskets.

This job isn't too bad....but I did it on the 240...not the 300. I'm not sure if space is a porblem with the 300s.

Anyway, drain the oil and remove the oil filter. Then begin by breaking loose the 5 allen head bolts that attach the oil filter to the block. You should be able to get the upper two bolts from the top and the other three from the bottom. All the bolts are the same length except for one (it kinda goes through the center of the oil filter housing to the block). This "center" bolt is longer and I had to file down one of my allen head wrenches with a grinder as I kept butting up against the engine mount or some other bracket and didn't have enough room to get the wrench on the head of the bolt in a square fashion. If you grind one down....make sure you "cool" the wrench as you grind (in a cup of water) so that the wrench does not lose its temper. Sometimes, when a person heats something up (like a wrench to bend it or to shorten it) the metal can get so hot that it looses its temper and is not as strong. If that will break it when you apply a significant amount of stress to it.

What ever you do, make sure that the allen wrench is on the bolt all the way before you try to break the bolts. The five bolts on my car were almost "welded" on and I had to be VERY careful that I didn't round off the bolt heads trying to take them off. One bolt was on there really really really tight and I was afraid I was going to break or round it off if I just didn't quit while I was ahead. But, I just made sure that my wrench was on there all the way and I kept at it until it broke free. As I said before, make sure the wrench in on there good and also use a quality wrench.

Once you get the 5 bolts broke, you should unscrew the black oil pressure line where it connects to the filter housing. I used an open-ended wrench to break that connection. Then use another open-ended wrench to break the two oil lines that go to the oil cooler. Once I broke those two lines, I loosened the brackets that holds the lines in place so I could move the lines out of the way. Part of these lines are made out of metal and don't want to move out of your way very well....that is why you have to loosen up the brakets that hold them in place.

Now you can take out the bolts (the bolt that is the longest and goes through the oil filter housing comes out with the filter housing itself as there is NO room to withdraw the bolt while the housing is on the engine.

Once you get that done you can take the housing off. It might be "stuck" a little....just wiggle it and it will come loose.

Take a gasket scaper and scrape the gasket material off the housing (be very careful not to put any gouges in the metal where the new gasket is supposed to go. Take some fine sandpaper and sand the residue off the sureface so that you have a nice and smooth sureface to put your new gasket. I used a very small block of wood with the sandpaper to keep the gasket surface smooth and to prevent myself from sanding a "hole" or "valley" know what I want the surface where you attach the gasket to be smooth and even. If you are replacing the oil pressure line gasket on the oil filter housing you should replace this before you put it on the engine.
Before you put the housing back on the engine, wash the filter housing out with mineral spirits (paint thinner) to clean it out good. You don't want to leave any old gasket material in there. Now you need to clean the engine block where the old gasket attached. Use the same method you used on the housing itself except I took a clean LINT FREE cloth and gently stuffed the holes where the oil passages are to prevent gasket material from getting into the oil passages while I worked on that surface. Don't stuff the material in the oil passages too want to be able to get them back out. Once I was done, I took some Q-tips and gently swabbed the inside of these passages to make sure I didn't leave any foreign matter in there. I really took my time during this stage to make sure that I didn't get any crap into the engine. This could be bad news if you do. Also, don't be too ruff with the Q-tips if you decide to use them...they can fuzz up and you can lose some of the cotton in there if you aren't careful. The main thing is to not leave any crap in the oil passages.

Some people will disagree with me on this....but I don't care. I used (and I suggest you do to) permatex aviation gasket crap on both of the gaskets I replaced. I wouldn't use a gasket maker material like the old RTV blue crap.....but this stuff is not like the others and won't squeeze out if you use a reasonable amount when you put things back together. Some say that you run the risk of having that stuff clog up the oil passages. Well, I doubt that Mercedes put these gaskets on dry and I didn't want to do the job over again. Know what I mean? Just be reasonable when applying the stuff and you will be fine.

The Aviation gasket sealer isn't fast drying so you don't have to run around like your pants are on fire to get the housing back on. Just put the sealer on and have someone help you (a helper from above and your from below to guide the housing back in place. I put all five bolts in the housing holes before I tried to put it back on so I could use the bolts and bolt holes to help guide with the proper placement of the housing. Whatever you do, make sure the longer bolt is on the housing before you begin to put it back won't go in its hole once the housing has been put back in place.

I waited one whole day before I started the car up. Permatex doesn't say anything about waiting....but I thought it would be best to give the stuff time to set up.

I hope this helps you with the project. As I said before, this was my only oil leak on the car. I wish it had taken car of the oil consumption.

Good Luck!

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Old 01-23-2002, 10:37 PM
Join Date: Jul 2001
Location: Old Lyme, Connecticut
Posts: 3,596

I have a 240D with a little higher mileage, but that runs great. It smokes very little, but loses oil. It took me a while to run down all the leaks, and the last one, the aft crank seal, is the worst offender. I do not intend to fix this as it is a big deal (you need to remove the engine, so I will park facing downhill to avoid more leakage than occurs when running) and I doubt you have the problem as it is very visible, under the car and on the driveway.

My older 240D developed a thirst for oil, and had no visible leaks. It turned out to be the valve seals, and once replaced the oil consumption dropped to a quart between 5,000 mile Mobil 1 oil changes. That problem showed up as significant smoking on start up if it was cold, or I rushed the process.

As noted earlier, if the car runs fine, the challenge is to find out where the oil is coming from. In all likelihood you are burning it and the conditions that allow that to happen do not exist at idle or when you can really observe what comes out of the tailpipe. At one quart per tankful of Diesel fuel, it will be apparent coming out of the tailpipe if you are behind the car when the conditions that cause the engine to burn oil exists. Try driving another car behind it on one of your normal routes and note when it starts smoking.

Hope this all helps and does not confuse! Jim
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)
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Old 01-24-2002, 07:18 AM
Posts: n/a
The good news about a diesel that uses a lot of oil is that if it starts and runs good you can keep driving it as long as you can carry enough oil with you to get where you're going.

In a gas engine this is not so. Once the engine starts using lots of oil, it will start fouling spark plugs and otherwise not run well.

The biggest down side is the hassle of keeping it full of oil, and the risk of letting it get low and spoiling the engine.

My advice is to keep it full of oil while researching and preparing for an engine overhaul. These engines rebuild well. If the pistons are okay upon inspection, you can replace the cylinder liners, lower bearings and do a valve job including guides and have it back like new.

Good luck,
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Old 01-24-2002, 08:12 AM
240Joe's Avatar
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Join Date: Nov 2000
Posts: 525
I can't resist...must do the math....

With no other performance issues, you can't economically justify the cost of a rebuild on oil consumption of 1 quart every 450 miles. It would take you 41 years of operation just to breakeven, assuming you drive the average 13000 miles per year, cost of a rebuild is $1500 (very conservative), and oil is $1.25 a quart.

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Old 01-24-2002, 02:06 PM
Posts: n/a
How much oil is being pushed out of the engine through the crankcase vent? If the valves have insufficient lash or the rings/cylinders are significantly worn oil consumption will go through the roof with the oil being blown out with the normal blowby gasses. I do think that you can burn a quart of oil per 450 miles without seeing smoke in your car. If your crankcase vent is circulating to the air cleaner remove it, tape the hole in the aircleaner with duct tape to prevent unfiltered air from entering the engine and let the vent blow onto the fender well. After a drive long enough to get the engine completely warm with some high RPM operation check the amount of oil on the fenderwell. You will see some oil, and that is perfectly normal, but if you get a significant amount you will know where the oil is going.

I am not sure on the 240, but the 300 engine valves are easily adjusted without the special or bent wrenches. It does help quite a bit to have one for the lower nut ground down to about .2" thick. Hope this helps.
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Old 01-24-2002, 02:40 PM
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I just found a special on the web for two of those "special" wrenches for 29.95. I wouldn't have bought them....but for that price (brand new too) I figured it was a good deal. I had been looking on e-bay for months for a used set and they sell for big bucks on there. I saw one auction where the set went for $90!

I also order (for $7 and some change) a set of valve stem seals. I figured I have nothing to lose by replacing them when I do my valve adjustment for the first time....sometime very soon. The new seals may help....they may not. I have a feeling that the rings and/or cylinder walls are very worn allowing excessive blowby and that is probably where I am losing my oil. I once took the oil cap off while the car was running and the "puffs" were about 12-15 inches high off the top of the valve cover and there was a fine "mist" of oil spray that came with the puffs. Given that information, does anyone think/feel that a quart of oil could be consumed in 450 miles?

As I said before, it is probably a waste of time for me to replace the seals....but it could help too. At any rate, I need to adjust the valves and I am just waiting for my new set of "special" wrenches.

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Old 01-24-2002, 03:17 PM
Posts: n/a
IMO, anything under 1qt every 500 miles and your in need of a rebuild. My Mercedes 617 engine manual states anything below 1qt every 200 miles in "acceptable" but I dont think so.

Drive 'em 'till they drop.
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Old 01-24-2002, 10:29 PM
Registered User
Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
Try new valve guide seals, and check valve guide to valve stem clearance at the same time.

I've listed instructions, as have others, in the past, do a search.

Bad valve guide seals will permit oil consumption of the range you have on an otherwise good condition engine. You will also have excessive blowby, especially if the guides are worn, too.

You will not see any oil smoke at this rate of consumption, except maybe a little blue puff when you start and after idling at a stop light.

And check the vent line from the vacuum pump to the intake manifold -- if you have a diaphram type pump, a leak in the diaphram will allow the pump to suck oil out of the engine and deliver it to the manifold!


1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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