MyE28.com

I have an 86 f350 6.9 when i bought it it was using oil so we tore it down and put a new set of rings in it. when we tore it down we realized it had all new gaskets in it and had been rebuilt recently. we honed it put new rings and lifters in it and put it back touno onlinegether. the truck still has alot of blow by and uses oil. i hauled a 13000 pound fifth wheel from ny to alabama. really slow but we made it. this year we hauled a pontiac vibe from ny to alabama no problems. only used 1.5 quarts of oil. when i city drive it uses more oil. i haul really heavy loads daily with no problems. now in service for 2 years. everything i see says if you have this much blowby your engine is toast. this truck runs perfect and starts perfect and purrs like a kitten. ????? what other issues would cause the truck to have this problem

Not sure how much similarity an old Cornbinder IDI has with a BMW turbo diesel but engines is engines to some degree.

Does this by chance have a turbo kit on it? Lots of them were installed. If it does it would be worth checking the intake plumbing to see if its got a noticeable amount of oil in it. Leaky turbo seals, restriction on the oil drain, or excessive crankcase pressure might cause that.

Were the valve seals replaced when the engine was apart? What sort of condition are the valve guides in? Don't know if the 6.9 is specifically prone to issues in that department but leakage around the valves definitely makes them suck oil. The clue that its top end and not bottom end is you won't have excessive blow-by. Blowby problems will show up as a lot of huffing out of the oil fill cap. Also not sure what these used for a crankcase vent setup but make sure thats proper. A lot of older diesels used what amounts to a draft tube, just vents to atmosphere through a hose, possibly with an oil separator to catch some of whatever huffs out. Sometimes that loops into the intake plumbing. That stuff can get clogged from old oil goo and once that happens it'll push oil-loaded vapors out of the crankcase wherever it can.