I did a search on that question and did not really find much so I thought I'd ask. I would also like to know what really says"give it up" on a diesel motor. My 1985 300TD Ca. version has what I would call a bunch of blow by. It won't knock the loose cap off but it does get a bunch of oil in the air cleaner(which drips from the center of the airbox). If I take the cap off I get a fair amount of steam 2.5 feet up before it breaks up. Other than that the car starts well, has a bit rough idle before it warms up and runs very smooth once it warms up, runs 80-85C on the highway in 37C weather with no air on and has good power. The car has new paint and looks great but the engine worries me. I just don't want to get way in and have the engine pop or do some bad things. So far, valves adjusted, rebuilt injectors, new filters and oil, replaced fuel lines, drive shafts, wheel bearings on the rear. The car sat from 1998 until I got it a few monthes back. It was supposed to have a new motor(10K on it) according to records then got parked???? The engine looks very clean and from that looks new. The blow by makes me think otherwise. I have not been able to do a compression check. It's not burning oil on the dipstick. The only other thing could be injector timing??? I do get a rough idle that the runs perfect then just hiccups then runs fine and does this until warm. I was also thinking it ran hot for some reason and may have damaged the rings?? Sorry for so much info and a long post. After all of this:

1. How much blow by is too much.

2. Can injector timeing cause blow by?

3. When should a person give it up on and engine?

4. Should I just keep driving it and not worry?

1. There is no such thing. As long as the engine runs well and does not consume a lot of oil, blow by is 100% pointless to worry about. The only time you should be truly concerned about blow by is during the inspection of a potential car purchase. Other than that, how much blow by your engine has is simply a curiosity. The only way to significantly reduce it (not possible to eliminate it) is to spend a few grand rebuilding the engine. If your blow by is only making the cap "dance", a rebuild would be a waste of money.

2. Not at all. Blowby is the passing of gas between the cylinder walls and pistons.

3. When it costs too much to fix/maintain.

4. Thats exactly what you should do.

The poll in this thread should give you some comfort.

OM616/617 Blowby survey

73% of us have some amount of blowby in our engines, including both of mine. Seriously, just drive the thing and enjoy it.

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1985 500SL Euro w/ AMG bits 130k
1984 300SD Turbodiesel 192k
1980 240D Stick China 188k
2001 CLK55 AMG 101k
2007 S600 Biturbo 149k Overheated Project, IT'S ALIVE!!!

[QUOTE=dirtcurt;1967034]I did a search on that question and did not really find much ...........................

Huh?

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Sam

84 300SD 350K+ miles ( Blue Belle )