6V92 smoke for first 1/2 mile when cold

[BG6]

It's a 1990 MCI 96A3 with 6V92.  I just picked it up 2 weeks ago, have driven it about 3000 miles.  On startup, there is a normal amount of smoke, and while idling to air up (there is a leak that bleeds it down within 5 minutes).  However, when pulling away the first time in the morning, it pumps out enough smoke to hide a naval task force.  This lasts for about 1/2 a mile, then goes away.

Any ideas?

[TomC]

Just signs of an engine that is on the worn side.  Eventually, it will have to be overhauled, in the meantime, try to warm it up more, or be lighter on the pedal so not to make so much smoke till it warms up.  I tight engine shouldn't smoke much when cold.  Good Luck, TomC

[bottomacher]

What color is the smoke?

[BG6]

What color is the smoke?

A medium grey.  Once warmed up, the smoke is gone except when I'm pulling a hill or from a stop, when there is a little black in otherwise clear exhaust.

[Diesel_Gypsy]

Check your airbox drains to make sure they are open. If they are plugged or pinched off, excess fuel and oil will pool up and then get blown into the engine when the revs come up.

Definitely a sign (as was said before) of a tired engine.

Later. . .
Jim

[BG6]

Check your airbox drains to make sure they are open. If they are plugged or pinched off, excess fuel and oil will pool up and then get blown into the engine when the revs come up.

Definitely a sign (as was said before) of a tired engine.

Later. . .
Jim

It seems to be okay once warmed up.  I had little problem going over the Grapevine and Donner in the last couple of weeks.

Okay, so what and where are the airboxes?  That term is a new one on me.

[Diesel_Gypsy]

BG6

All 2 stroke Detroits have a blower to blow combustion air into an airspace around the cylinder sleeves before it enters the cylinders for combustion. If your rings are worn or stuck, some oil will slip past and gather in the bottom of this airbox. Also if you have a weepy injector or poor combustion (maybe because compression is down?), the excess fuel will migrate here also.

When you start driving, the air starts moving through the engine much more quickly and takes the accumulated oil/fuel with it. This causes your smoke until it clears the crap out. The engine will run on this too,  so don't be alarmed if the rpm's start to run away a little. Try not to let the engine idle for long, especially slow idling when it is cold.

Detroit knew all about what happens in there so they provided a drain on each side of the engine to let the majority of the crud leak out on the ground.  The environment (or your driveway) wasn't much of a concern back when they designed these things.

Some people didn't like this dribbling on the ground, so they started running the drains into a little pot that the owner could discreetly empty into some sanitary container, thereby preserving their beloved bus's dignity!

Have a good one. . .
Jim

[happycamperbrat]

Do you know of any photos so that I can see what this air box looks like and what to look for on my engine? It isnt smoking or anything, but this does sound like something I want to check out. Thanks!

[JackConrad]

Do you know of any photos so that I can see what this air box looks like and what to look for on my engine? It isn't smoking or anything, but this does sound like something I want to check out. Thanks!

No photos (yet), but the air boxes (one on each side of a V engine) are part of the block and have inspection plates bolted to the sides of the block under the exhaust manifolds (one inspection plate per cylinder) each air box has a 1/4" drain tube. I have seen a couple 8V71s that had the drain tube plumbed back into the engine through a one way check valve.  Unless you have a problem with excessive smoke on start-up, I would not mess with them.  Jack

[Utahclaimjumper]

I have the factory recovery kit on mine since new and it works well.>>>Dan

[RTS/Daytona]

happycamperbrat (aka ablueprincess  ??)

Your RTS has a air box collection device - CONNONLY CALL THE SLOBBER BOX or SLOBBER TUBE - (I never seen it in the RTS maintenance manuals or RTS parts books ) it's about center of the RTS bus - right next to the oil pan - it's about 2-3" round about 8" tall - sits upright - has a HUGE nut with a pipe hole in the center on the bottom for draining - It collects the overflow and doesn't leak till it's full (that pipe at the bottom goes up about 1" from the top and drains the overflow) - ask me how I know - I'll tell you away - when it's full and you go over a driveway at a angle so the RTS is tilted - It leaves a trail of oil

It's usually emptied only when you do an oil change - tell the guy doing your service to locate the air box collection device (SLOBBER BOX) and drain it - If you don't idle your RTS much (and you shouldn't) - it will take a long time to fill if your engine doesn't smoke much when it's cold

Pete RTS/Daytona

[happycamperbrat]

Okay, I'll check it out! And yup Pete, my cover is blown