OM616/617 Blowby survey

[DieselAddict]

I've been reading the archives on blowby but I didn't get a good idea of how much blowby is normal on these engines. So I thought it might be useful to do a survey. I understand there is more than one method of testing blowby, but it seems like loosening the oil cap and observing its motion is the easiest and probably most accurate method. So if you're interested in submitting your results be sure your engine is hot when you do the test as engine temperature will affect the reading. You can also specify the year, model and mileage of your car by replying to this thread. Beware of oil droplets flying out and protect your eyes!

My E300's oil cap just sits there with the occasional twitch, but my 240D's oil cap really dances around. I know they are completely different engines so they probably have different standards of blowby. Please submit your results to the poll only if you have a 616 (240D) or 617 (pre-86 300D/SD) engine. But you can submit results for other engines by replying to this thread.

[mac2]

1976 300d
162,000 miles (5 digit odometer, could be quite bit higher)

Cap test (approx 3 min after start):
Perfectly still. Pulling on the cap it seems to be pulled down by (very) little suction.

After a hard drive:
Just sits there maybe swiveling around just a bit.

For a $500 car it has an excellent engine.

1982 300TD
320,000 miles

Cap test air temp at startup: Dances
Cap test 82*c: Stays still. Mabye a jitter every so often.

[iNeon]

i CABT be the only one with a tired engine!

the car is a 79 249d, 145k on it.

i dont know how bad the blow-by is, but i did leave the oil cap off once when i changed the oil... my poor fenders looked like dalmatians

thats why i voted for high blow-by. maybe the two arent related?

Originally Posted by iNeon

thats why i voted for high blow-by. maybe the two arent related?

You have the cam lobes, valves, and valve tappets right under the cap to fling oil everywhere.

[DieselAddict]

Originally Posted by ForcedInduction

1982 300TD
320,000 miles

Cap test air temp at startup: Dances
Cap test 82*c: Stays still. Mabye a jitter every so often.

Hmm, that's weird. My car is the opposite. With the engine cold the cap just sits there, when it's hot there's lots of dancing.

[Hatterasguy]

My 617 will make the cap dance. I'm kind of disapointed because it only has 220k miles and I know the po was big into oil changes and maintaince. My guess is those are around town miles.

603 nada, slight suction maybe.

[Glinko]

The oil cap flew off and hit me in the forehead.

[sailor15015]

Just dances a little bit after about twenty minutes of highway driving. A little bit of oil will drop out. Haven't tested it cold.

Originally Posted by Glinko

The oil cap flew off and hit me in the forehead.

That explains a lot.

[Maki]

I've got an '82 300cd with pretty serious blowby. The filler cap dances around violently, and if I don't make sure the dipstick is firmly seated in the tube the crankcase pressure will push oil out of the sump. After about the third time this happened I replaced the O-rings on the stick -- that seems to have helped.

Still, the car starts easily down to zero F without a block heater (it doesn't have one -- the car is originally from southern California). The power is fine and the engine idles smoothly and barely smokes. It burns and/or leaks about a quart of oil every 1200 miles.

[DieselAddict]

Actually you're not the first one who has blowby but apparently good compression. From what I've read leaking valve seals can cause blowby too, but wouldn't that reduce compression as well? One day I may do a valve job on my 240D to see if I can reduce the blowby and oil consumption, but my oil consumption is not very bad at this point, I think it's about a quart per 2000 miles.

[the tenor man]

I had a 1977 240D and the blowby was so bad it soaked the air filter to the point of oil dripping on the ground. I believe later models had a chamber under the filter (intake manifold?) that let the blowby oil drain back into the oil pan.

I rebuilt the engine (pistons, rings, valve guides, valves, oil pump etc.), drove the car for another ten years (150,000 miles) and sold it on ebay when it turned into a rust-buggy...and it still had blowby...but it ran!

I think I would have to describe the cap (before rebuilt) as "blowing off" and after the rebuild as a "dancer"...

Hope this helps
The Tenor Man

[samiam4]

Actually you're not the first one who has blowby but apparently good compression. From what I've read leaking valve seals can cause blowby too, but wouldn't that reduce compression as well?

NO valve seals will not effect blow-by. Blow by is due to lack of sealing between the cylinder on compression stroke and the valves would be CLOSED, so valve seals wouldn't effect it.

I don't think blow-by is a good criteria- I've seen great engines compression reliable cars with blow-by. For a gaser- it's a better measurement.

Why mess with oil consumption @ a quart/2000 miles? MB spec for repair is 600 miles per quart.

Michael

82 300D Turbo
304K miles - head has never been off AFAIK
cap "moves around slightly" and blows small amount of oil onto valve cover.

I check the 240D when I can get it away from my wife for 2 minutes.