On Sun, 05 Mar 2006 22:59:31 -0500, Larry wrote:

Larry wrote in
:

I could see it would carbon up if you just ran the engines in an
unloaded condition in neutral for long periods of time....

Thinking about this, I cannot help but think about those engines in the
big trucks that are left idling for 8 hours, virtually unloaded, while
the driver is sleeping in his sleeper at the truck stop. I suppose he
burns off all the deposits when he drives off down the interstate in the
morning.

Obviously, 8 hours of idling while sleeping, followed by 8 hours of 80
mph under load, followed by 8 hours of idling, again, isn't hurting
Cummins engines much. Hell, they don't overhaul them in the real world
away from the service manual until the clock says 400,000 to 500,000
miles...or more.

What about my diesel cars that hardly ever leave the city? I've never
seen this phenomenon while sitting in the traffic for hours on end,
idling along to the next traffic light.....??

Maybe it isn't as serious as it's imagined.....?? My 73 220D was
overhauled at 300K after 28 years on the road. Its exhaust always
looked black and oily, especially if you brushed your pants against the
pipe getting the load out of the trunk. I saved a piston and the valves
from the overhaul junk pile. There wasn't any kind of hard coked
deposits anywhere you couldn't wipe off with a shop rag....

Automotive/truck diesels are different, designed to run at light load for
extended periods. Marine/industrial diesels are designed to run at high
load all the time, like a truck pulling a full load over an endless
mountain pass. Of course there's some crossover, but for the most part
these are different types of engines.

Matt O.