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So i have a 91 f 250 diesel 7.3 liter not turbo i have had problem with with smoking whitish blue smoke when just starts and then goes away just a puff between shifting could this be injectors any info would be great. truck runs great and will pull anything would like to put aftermarket turbo on but want to figure out smoking situation first if its even worth it. also the antifreeze disappearing and i cant figure out where it is going the oil looks good and have done oil changes and just looks like normal dirty oil. please please help thanks.
 

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White/Bluish smoke is the results of cold engine starts. A "Long/Slow RPM" start of more than ~3 seconds Tends to load the cylinders with a fuel/air mixture similar to a gas engine that is flooded, leaking injector. The White smoke is unburned/partially burned fuel, the Blue smoke portion could be crankcase oil, the pistons/cylinders are flooded by oil jets, if the piston rings are worn/stuck, some of that oil can get into the combustion and exhausted along with the unburned fuel. For a "complete" fuel burn/combustion, the cylinder (combustion stroke) temperature has to reach 945*. The cranking RPM has to be at least or more than >150 RPM.

As far as loosing coolant, it could be a head gasket leak. A compression test might tell you if you have one or two cylinders that are low (~260 PSI) compared to others, 260 PSI to 450 PSI is acceptable as long as there is not more than 50 PSI between the Hi and Low.
 

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^^^What he said. Keep in mind that a smoke problem could be something as simple as a dirty air filter. Then something not mentioned in the above post would be the possibility of worn valve guides. You might also see if maybe that smoke is actually steam.
 

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My similar problem ended up being old, weak injectors, I guess they were no meant to go 280k.
 

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At an average of 1800 RPM, those injectors opened and closed about 63,000,000, that's Billions of times. Pretty well worn out at 280K miles.
 

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Typically it is just a cold start. My truck does it every time I cold start it. Nothing really to worry about. However, if there is an extreme excess then you might have some pressure in your engine that could lead to more serious problems. A way to check is to take the coolant cap all the way off and then set the cap on the hole where it screws in to (do this on a cold start). If the cap is popped off then you have a seal that went bad which doesn't restrain the pressure well enough.
 

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A way to check is to take the coolant cap all the way off and then set the cap on the hole where it screws in to (do this on a cold start). If the cap is popped off then you have a seal that went bad which doesn't restrain the pressure well enough.
I have heard of doing this with the oil fill cap.
 

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I think he means the oil fill cap, some genius posted that on another site and expected anyone lacking in brainpower to go for it. First of all that "test" means nothing unless the CDR is blocked off so blowby (crankcase pressure) can't bleed off through it, not to mention the fact engine vibration would knock the cap off while cranking let alone idling. Secondly, the only way to check for excessive blowby is block off the CDR then check crankcase pressure with a manometer plumbed into the oil fill tube. Anything over 6" on the manometer at max RPM is excessive blowby according to FoMoCo and Navistar's allowable spec.
 

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A good indication of blow-by without the test equipment is to take the oil fill cap off and see how much vapor comes out. Egine warm and running, there will atways be some, but it shouldn't be blowing out like a chimney either.
 
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