My 79 SD has unknown mileage and no service records. It runs well and is strong enough to use comfortably as a daily driver. I have replaced the fuel return lines, the bad glow plug, the fuel shut-off valve, changed the oil and tranny fluid. I considered next doing a valve adjustment, but there is quite a bit of blowby evident when the oil cap is off while running. Will a valve adjustment do much good at this point? Should I set my sights instead on a top end rebuild?

Wouldn't the blowby be a common result of the valve adjustment being neglected? My theory is that the valves being slightly out of position at the time of explosion would lead to excessive wear.

A valve adjust will not affect blowby. This is only affected by the piston rings. The valves only connected and disconnect the combustion chamber the intake and exhaust manifolds.

You might check that the breather lines to the intake manifold (before turbo charger)are not clogged and if they are, clean them out.

P E H

Blowby is typically caused by compression leaking past the piston rings. If for some reason your valves were leaking, they would leak either into the exhaust or back into the intake - not into the crankcase.

A valve adjustment is a worthy maintenance task if you are unsure when it was last done.

As far as the blowby goes I would ignore it if the tube from the valve cover to the air filter housing is adequately handling the blowby. That is, there is not excessive oil splashed all through the oil filter housing.

Are you getting any oil smoke, either on startup or while generally running around?

Ken300D

She doesn't seem to be burning oil. I get a fair blast of smoke at start-up, but it appears to be white and not bluish. This is not as bad since the new GP installed. I believe that the white smoke is reduced because there is not so much unburned fuel with all cylinders heated at start-up. She can give a pretty good blast of smoke when leaving a from a stop or hard acceleration.

mccan,

You've made two statements in your posts that indicate you need to quit worrying about blowby and just properly maintain and enjoy your diesel. It doesn't burn oil and it starts and runs good. As a previous poster said, keeping the valves adjusted is a worthwhile maintenance procedure.

Diesel engines can continue to be driven with no harm as long as they start, have oil pressure, low enough coolant temperature, enough fuel in the tank and you can carry enough oil with you to get where you're going.

Adjust those valves, keep that oil changed, do the other preventive maintenance when due and enjoy your clackin' diesel.

Have a great day,

ok Larry - the question of the day.
As you know I am in the process of putting one of these works of art together (240D and I am serious). I have the option of running a 1980 manifold that does not have the cyclone separator or running the manifold with the separator. I have attached pics of the two different manifolds in addition to a pic that shows the one without bolted up. Which would you run? I did notice that the one with the butterfly (which allows for the separator to be bolted up) had a pretty heavy amount of oil/tar like deposits built up in it.

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Jim

manifold on left is off of a 1983 engine and allows for bolt up of oil vapors/liquid separation with liquid being returned to oil pan. Manifold on right shows 1980 manifold without liquid return. Also, manifold on the left has a butterfly that is operated by the mechanical throttle linkage. I'm not too sure what the butterfly is in there for. There are no butterflys in the intake of my 300D.

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Jim

picture is courtesy of another mercedesshop.com member.
Which one would ya'll install on a newly rebuilt 240D engine? I did notice that the 1983 manifold has a very severe build up of oil/tar in the intake where the 1980 manifold is clean in comparison. I really do not like the idea of the butterfly in the intake on these engines.

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Jim

Well, clearly in the 1980 mainfold you burn all blowby. In the 1983 manifold you get some ability to recover liquid oil and return it to the crankcase.

On the W123 300D (Turbo) this function takes place in the air filter housing, which is considerably cooler than the intake manifold. But liquid oil probably isn't going to burn all that much while still in the 1983 240D manifold.

You'd have to think the 1983 manifold is a bit of a design improvement - although it may be mostly with the idea of reducing emissions. If your car has minimal blowby then either manifold should work fine. I see you have the 1980 one bolted up already.

Why don't you go with that one (1980) at first and see if you get much oil smoke after breakin? It seems the 1983 manifold would come into use later in an engine's life when there is more blowby.

You probably plan to keep the 1983 manifold - so its available if something unwanted starts to happen with the 1980 manifold. Of course I would expect there is an unused return hole to the oil pan you have to plug?

Ken300D

Thanks Ken - that is kinda along the lines of what I was considering doing - going with the 1980 intake and then if oil consumption is real high install the original 1983 manifold with the separator. Unfortunately, the pic showing the bolted up manifold is not mine. My engine is still in pieces. Hopefully, I will get the block, crank and head back from the shop this week. The car is an '83 and I purchased a complete - non-running 1980 engine so I have two oil pans - one with the return hole and one without. I just wanted to get some opinions - I think like L. Bible - the simpler the better .

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Jim

Jim, I have the oil separator system on my 82 240D. It is a source of considerable oil leakage (not quanity - just messy). The hoses and plastic parts are not designed to handle much pressure. It would be nice to have the setup in the bottom picture - simpler and only 2 leak points instead of 6.

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1976 240D
1987 560SL
2007 E320 Bluetec
1998 C280 (now son’s car)
1982 240D Manual - Sold

Thanks L. Bible, Ken and PEH. You guys have already added a lot to my experience with this car. I'll proceed with valve adjustment. First question: should I go ahead and replace timing chain? I don't know how old the curent TC is (could be original) and as catastrophic as a broken one can be I figure I might as well replace. Next question: what grade oil should I be using? Do you adjust grade of oil for age/blowby, et.?
Thanks again, gentlemen.

If the chain adjuster will keep the chain tight, it does not need to be replaced. THe chain only breakes when something else fails such as the chain adjuster or the chain guides. Check the cam timing (do a search). If is 3 degrees or less you are OK.

You seem to be a worrier and owner of gasoline engines that always need fixing and maintenence. If the engine starts easily and runs good, there isn't much wrong with it. That's the beauty of a Diesel, they last time and need minimum repairs and maintenance. Just do the mainternance of valve adjustments and oil and filter changes.

I use Castrol 5W50 synthetic in the car I use winter and summer and Mobil I 15W50 in the cars I use only in the summer.

Thanks P.E. Definite adjustment from old 911 to this diesel. I read in this board's archives that dirty oil can wear down the Timing Chain and provide cause for replacement. When I got this car the oil was old and solid black. And I have no idea how long since last oil change. Thanks for the tip on cam timing.

When you change the oil in a diesel it will be "old and black" again in about 100 miles. There's a lot of soot blowby in a diesel that really makes the oil get dirty. That's why you need something diesel-rated (a good detergent oil). A good oil will keep the soot suspended so that if you change regularly it will be washed out with the old oil.

Thus the recommendation to warm the engine up completely (like on the highway) before pulling in to change the oil. This helps the oil to have maximum suspension of soot when changed.

You're just gonna hav'ta choose your own oil brand, 'cause if you ask here this thread will grow to 500 posts in a weekend.

Ken300D