Okay I've got a 1979 240d that has plenty of power (for a 240D), runs
smoothly and has none of the usual outward signs of low compression. Always
starts on cold days, no oil residue at the tail pipe and like I said pretty
decent power. I have changed my valve cover gasket and oil filler. But I
can't figure it out. I alway assumed that if a car has blowby I should be
able to see some signs at the tail pipe. Any thoughts???
At the tail pipe you won't see any evidence of the engine burning oil.
It's the blue smoke screen that you leave behind that's telling.
If the diesel starts well in the cold and has reasonable power - all 68
HP - then the rings and compression may be OK. You didn't say how many
miles are on this engine, if over 250K it may well be worn and the oil
burning is a sign of that.
You've evidently tried to fix some oil leaks with new gaskets. This
engine has only a few leak sites, valve cover, bottom cover and the
crankshaft seals - front and back. The vacuum pump on the front of the
engine is another possibility.
Blow by is from combustion by-passing the worn rings and creating
pressure inside the engine that forces oil to leak from the above
On the top of the valve cover is a hose to carry the crankcase fumes to
the intake manifold for disposal. It could be that this hose is clogged
and/or that the screen inside the valve cover is so dirty that oil that
should be drained off is being forced into the intake manifold and
consumed. This is more possible if the engine runs too cold - without a
80 degree C. thermostat.
The engine has about 350K+ on it, but it doesn't leave the telltale blue
"smoke screen" that is evident of worn rings either. I will look at the
thermostat, and check the screen too. I know I'm tilting at windmills
hoping for a cheap fix when none is available, but I can hope......
I'm not leaving any puddles that I can see. It is a quandry. I don't see
how a car can burn that much oil and not have a white cloud and leave a
noticable residue around the rear end. Any other thoughts? I will check
the oil filter too!
clean it up with GUNK spray cleaner as best you can.
let dry then start it up.
look for any leaks. shut it down after 20 mins.
try to put a large box under the car & check it for spots after a few
if your burning a QT every 100 miles there ain't a BUG within miles of
the case, minus a few cans!
O pleeze. The man's loosing a quart every hundred miles. One quart of oil is
sufficient to cover the entire car; there's no need to look under the
carpets or in the trunk or even wash the engine. A diesel normally burns
oil-fuel oil- without (much) smoke. Why should lube oil be different?
On Tue, 16 Nov 2004 23:40:27 -0500, "Chas Hurst" wrote:
Could it be that this car is blowing pressure past the rings,
pressurizing the sump and blowing oil out the breather (into the air
filter usually), this would then be drawn into the engine and burnt
(I.E. vanish). This may explain a loss of oil with no visible puddles.
It would of course be worse when the car was cold, so rough idle when
cold maybe. A little smokier when cold too perhaps. But Chas is right
isn't he, if this engine can burn diesel oil without smoking, why
can't it burn slightly thicker (and clean too if it's having a litre
of oil added every 100 miles) oil with very little smoke.
If this type of scenario is plausible, then it could also be a head
gasket leaking pressure from one or more cylinders into an oilway;
thus pressurizing the sump that way?
Don't shout at me, it's just a thought!
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.