[Vwdiesel] OT, problem with a different diesel engine

[David Cook]

Hey all-

My school bus exhibited a couple strange symptoms
while on a field trip tonight.  I was wondering your
thoughts before I mention it to the mechanics.  (I
want to look smart!  Well, that and I am just really
curious.)

Anyway...

The bus is a '94 model International turbo diesel
engine, it has no computer controls or anything like
that.

If I'm driving along really pushing it, the engine
will start making a rattling noise.  It is such a
rattling noise that at first I thought it was the door
handle rattling.  

It will rattle for a half second or so, then stop
briefly, then rattle again.  Like
"da-da-da-da-da...da-da-da-da-da...etc"  When it is
rattling, I notice a very slight reduction in power,
though the bus doesn't really slow down.

Also, during a time it is doing this, I have noticed
that accelerator pedal action is delayed.  I mean, if
I press the pedal down, it will act like it didn't
know I did that for about half a second or so.  And
then, if I let up on the pedal, again there is about a
half second or so delay before the engine speed drops.
 

The pedal itself still moves smoothly.

The really odd thing is that the bus has to be driven
for a long time before this happens--at least about an
hour.  I can drive it as hard as I want for up to
about an hour before it will start making this noise.

Today, after my afternoon route, I took an athletic
trip.  After driving the afternoon route with no
issues, we took off for the athletic trip. 

It wasn't very long before the rattling started.  At
one point, we came to a stop light.  I slowed down
slowly, and put it into neutral as we approached the
light.  The engine stumbled just a tad-dropped to
slightly lower than normal idle speed-for a second or
so, then settled at normal idle speed.  

After the light changed, I took off again.  We drove a
few minutes  before it started rattling again.  As we
came to an on-ramp, I put it in neutral again to see
what would happen.  To my surprise, the engine
immediately died, but started up again.

At the next stop (a few miles of rattling down the
road to get on another highway) I again let it slow
down slowly, then put it in neutral as we waited at
the stop sign.  It idled normally.

On the new highway, I decided to not push it as hard,
and kept it right at about 55 mph.  We went the whole
rest of the trip (about 45 minutes) with no rattling.

I decided to do an experiment on the way home.  As we
got on the highway, I drove pedal to the metal the
whole way.  

It was a whole hour before it started rattling.

The reason I ask is that this seems so odd to me, the
fact that it has to have driven so long before acting
funny.  Its not like it just waits until the engine
warms up or something, obviously the engine has been
at full operating temps for a very long time by the
time this happens.

Anybody have any ideas?  Again, the engine is all
mechanical, as in no computer controls.  It also has a
4-speed allison auto trans.

Thanks,

David

David Cook
Red '86 Cabriolet Diesel Powered
Red '90 g60 Corrado 
Brown and White '78 Westy Campmobile "Bear"
and others in various states of disrepair
Pictures here: community.webshots.com/user/superdave5599

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