[Vwdiesel] OT, problem with a different diesel engine

[Scott Kair]

	We've been using the IH/Navstar 466 engine with Allison automatics
for several years in our work trucks.  They're far from delicate, but
institutional maintenance procedures are often determined by bean counters
rather than mechanics. What you describe should be brought to maintenance's
attention, if only to cya.
	In the pre-electronic models, we've had a few instances of
accelerator linkages having to be replaced due to wear on the pivot points
and springs.  While there might be some linkage involvement aggravating the
problem, I don't think it's the primary problem.
	The first check would be the fuel filters, and then a thorough check
for contamination.  Institutions tend to buy low-bid fuel, and while the 466
isn't as sensitive as a current generation Eurospec VWD, it's not unknown
for low-bid suppliers to stretch their supply with questionable additives.
The newer, electronic versions are particularly sensitive to fuel quality.
In the electronic versions, the first step the dealer takes in investigating
possible injector issues is a cetane test. If the fuel measures below the
required standard, which most does, the warranty doesn't cover the repair. 
	Valve adjustments tend to be overlooked, too.  Since it requires
specialty tools and some shop time, it often has to be farmed out to the
dealer, where shop rates are truly frightful. The injectors seals can also
fail, allowing extra air into the chambers. 
	We've also had a couple of episodes of injector tips detaching and
dropping into the combustion chamber.  That usually leads to a very quick
catastrophic failure, but one of them went a couple of days with smaller
chunks rattling around.  An infrared thermometer will reveal one or more
injector & chamber running cold if the engine and turbo haven't turned to
shrapnel yet. 
	Finally, keep an eye on coolant and crankcase oil mixing.  We've had
four in for teardowns and rebuilds in the last year for this.  Two instances
were caused by kids not watching coolant levels and temp gauges, but the
other two are still damifinos. The parts bill for sleeves, pistons, rings,
gaskets, etc. isn't pretty, and dealers seem required to send at least one
set of wrong parts.
	Keep us posted, and hth,
	Scott Kair     

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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