I posted this on another thread, but thought it would be helpful here.....
I just bought my 2004. 5 CTD 3 months ago off Ebay from Dallas. Truck has 112k and appeared to be in excellent shape all around. I just noticed some oil buildup around blowby tube on side of engine and on front differential. Bottom of truck was unusually clean and was likely steam cleaned. I figured no big deal for a truck with this kind of mileage. However, after parking truck over night I noticed 4 inch puddles of oil under blowby tube & front axle. After my first long highway drive (3 hours) the entire bottom of the truck was coated with oil and had oil spray on tailgate. Funny thing is truck starts right up in cold weather, runs smooth, doesn't smoke (unless you really punch it - black smoke), appears to have good power, gets 17-18 mpg in town and 20 mpg highway and doesn't seem to use alot of oil. Oil analysis showed only a slightly elevated iron content (probably cylinders wearing). No evidence of piston, bearing or ring particles, anti-freeze, water, fuel or soot in oil.
I noticed pulsing white/steamy smoke coming out of oil fill cap opening when engine is idling. Force will blow cap off engine. Same smoke can be seen coming from breather tube under engine - but you have to get under truck to see it. I did alot of research on all the CTD sites and concluded I had an excessive blowby problem. So I brought it to a Cummins dealer last week for testing. They did a blowby test using a Manometer and the engine raised the water column a very high 30 inches (factory spec is 10 inches). They checked turbo - ok. Compression test came back 150 psi cylinder #1, 450 in #2, 200 in #3, 200 in #4 (he didn't test cylinders 5 & 6 because he got enough bad news). Factory spec is 350 psi. 150-200 psi is low compression for this engine. The mechanic thinks the excessive blowby is coming through worn or cracked rings/cylinder wall scoring. He didn't think it was a hole or crack in piston or a valve problem. However, he would need to pull head off to be certain.
The injectors all looked good, no high performance mods noted, engine looks stock. Eventhough the intake system and turbo fins were clean, he suspected the engine got DUSTED by the fine dust in the plains of Texas. I have read that there is alot of controversy about "dusted" engines. I live in Connecticut but he has serviced trucks up from the southwest that suffered similar problems.
BOTTOM LINE - REPLACE ENGINE !!
REMANUFACTURED SHORT BLOCK (pistons, rings, rebored cylinders, bearings) $7-8,000
REMANUFACTURED LONG BLOCK (short block plus remanufactured head) $ 10-11,000
He recommended a long block because having a new, high pressure bottom end would possibly harm a high mileage valve train and suck a valve or two - SAY BYE-BYE TO NEW ENGINE.
Also due to mileage, he recommended replacing turbo because an older worn turbo can blow out seals and blow oil into cylinders and explode, causing engine to overrev and self-destruct - SAY BYE-BYE TO NEW ENGINE. Just add another $2,000
$10,000 - 13,000 to fix my problem. Also since the engine and transmission have to come out might as well install new clutch, throwout bearing and input shaft seal.
I bought the truck for $20,000 and am having a hard time justifying putting that kind of money into it.
I have a friend who owns a machine shop and he said if I pull the engine out myself, he can rebuild it to factory specs for alot less - He is working a getting me part prices so I don't know total estimate.
The mechanic said I can still drive it, but check the oil every day and be aware that one day the engine could puke alot of oil in a very short time and cause major engine failure.