My new "little mule" is an '86 250 with a 6.9. It wouldn't start when I bought it. The previous owner had put in a rebuilt motor, says it has 1000mi on it. I checked & changed several glow plugs on it and it now starts & runs well, however: I seem to be getting a lot of blow by, to the point where it is quite visable. Would this have any thing to do with the air cleaner? It is one of those "life time" breathers. It runs to a "Roto-Master". Between the air cleaner and the turbo there is a 3/8" tube open to the atmosphre. Any Ideas?

Great board, already been lots of help!

 

By nature, diesels are born with blow-by. If the engine is fresh, then it might need to be broken in. I would put about 5000 miles on it before coming to a conclusion. If there is an oil residue coming out of the tube then I would be slightly concerned. How much oil do you burn between changes?




1986 F-250 6.9 diesel,4x4,XLT Lariat,Ex Cab, 8'bed,etc...

 

Thanks! Don't know about comsumption yet. The turbo oil return hose was leaking at the pan and I just got it stopped. Would a dirty air filter effect the blow by?

 

Any time there is an opening between the air cleaner and the engine, there is a chance of the engine ingesting dirty air. This WILL cause excessive wear of the pistons, rings, cylinder walls, valves, guides, all contributing to excessive oil consumption. BUT, if the rebuilt engine was not properly run in, the rings may not have seated properly to the cylinders. You may have some success trying to reseat the rings by avoiding light loads and idling, and running your truck around three fourths to fully loaded at varying speeds, keeping an eye on engine temp. youdon't want to overheat the thing, but you do not want low cylinder temps for any length of time.(remember no idling and no light loads) If you can try to duplicate these conditions for at least 100 miles, you should at least see a difference in the amount of blow-by vapor from the crankcase breather, and a change in oil consumption either for the better or worse. Good luck.