Hello
everyone, and thanks for checking out this post. I recently worked on a customer’s
4300 that was burping coolant out of the expansion tank. It is a 2005 EGR motor
with 500,000+ miles that is kind of a frequent visitor to the shop. We have
replaced 5 of the injectors, the radiator, and a fuel transfer pump over the
past few years, but it remains a fairly good running truck. The customer
delivers a product requiring a special cargo lift to a large geographical area,
so their trucks tend to be in service a long time and repairs must be turned
around as quickly as possible.
The truck
actually came in with an injector miss in #4 cylinder. After a road test to
confirm that repair, I saw coolant escaping from the fill cap. When the
radiator cap was loosened immediately after the drive, several gallons of
coolant exploded out of the reservoir. The problem was not accompanied by
overheating at least not for the limited drive I took, but it was obvious I was
getting excessive pressure in the coolant system.
Having seen
this happen if all the air isn’t purged from the system when filled with
coolant, the first thing I did was to ensure the system was filled and no air
was trapped. The upper radiator pipe going across the front of the engine has
an air bleed on it that must be loosened while filling. Most trucks will have a
petcock like a radiator drain on the system high spot, but this model has a
plug sealed with an O-ring and these will usually seize and won’t loosen. As a
consequence they often aren’t bled properly when filled. As the truck recently
had a hose replaced on the road, I needed to be sure there wasn’t an air bubble
causing the problem. I warmed up the bleed fitting boss with a torch, twisted
the plug out, welded a nut to it, then reinstalled it with a new seal and some
anti-seize so it could be easily removed next time.
Of course
the same condition was present after another drive, so work continued. I
replaced the reservoir cap with my pressure tester and found the pressure built
at idle at a rather alarming rate. After eliminating the air compressor by
clamping its coolant hoses and idling again, I used a test kit to check for
combustion gasses in the coolant, which confirmed the pressure was coming from
a cylinder. Assuming I had a head gasket problem, pitted liner, or a head
crack, we got the OK to pull the head. The rest of this post will illustrate
the danger of making assumptions, even after years of working on a particular
engine.
Normally I
remove the injectors when pulling a head. It is just too easy to damage an
injector tip when removing or installing the head, not to mention the care that
needs to be taken when cleaning or moving the head around. It just isn’t worth
the trouble. I also usually pull the injectors fairly early in the head removal
process, in order to catch any injector, cup, or head issues early in the job.
However, we had replaced 3 of the injectors in the past couple of years and
didn’t see any of these problems, so I waited until the end of the day for
injector removal. When I went to pull the #1 injector, I found it stuck. Unlike
the earlier DT, the injector hold down in the EGR (2004-and up) motor extracts
the injector as the hold down bolt is loosened. This one however, didn’t move
and the effort required to turn the hold down bolt after the first few
revolutions told me there was a problem. I tried to pry the injector up with a pry
bar, but it only moved a fraction of an inch. Assuming the injector was coked
in with carbon, I poured a little intake system cleaner around it and let it
soak overnight. At least it looked like I found the problem and the head
probably wouldn’t need to come off.
The next
day I managed to get the injector pried out with a large ladyfoot pry bar, and
it was indeed coked up. If for whatever reason the injector doesn’t seal to the
bottom of the sleeve, combustion gasses will enter the sleeve and the carbon
and soot will accumulate and harden around the bottom of the injector. This can
make the injector very hard to remove. The problem can be caused by the
injector not being seated properly when installed, an improperly torqued or
broken hold down bolt, a missing or damaged injector tip sealing washer, or a
leaking sleeve. In this case the hold down and bolt were ok, torque seemed
good, and the metal bottom seal was in place, so the cup was suspected to be
damaged and leaking. The lower injector O-ring, which seals the fuel passage
from the sleeve and coolant area, was in bad shape from the heat and pressure
it had been subject to, and it would probably have failed before long.
The
injector sleeve needed to come out, but the problem was that the sleeve remover
we had for the DT 466/T444/7.3 would not work in the Maxxforce, as the sleeves
are different size. We actually only found 1 source for the correct
remover/installer kit, and it was expensive. Some research however revealed
that the DT365/Ford 6.0 engine uses the same cup as the Maxxforce, and 6.0
tools are easy to come by, and cheaper. Maybe tool manufacturers don’t want us
to know that the tools for both engines are interchangeable. One manufacturer
actually lists a separate part number for each of the two kits and they are on
the same web page, with no indication that they would each work on both
engines. Not having the two injectors available for a side-by-side comparison I
can’t say the two don’t differ in length or some other trivial dimension, but
since the cups (sleeves) used are the same, the tools for all practical
purposes are interchangeable. The short story is that we got a kit for the 6.0.
and it worked.
When the
sleeve was out there was an evident track where it looked like combustion gases
had been passing from the injector tip hole and across the bottom of the
sleeve. The sleeve didn’t appear to be cracked or otherwise damaged. This led
me to believe that the sleeve had lifted a little in the bore, causing both excess
pressure in the cooling system as well as the coked-in injector. At least that
is what I hoped. Whenever I have a problem like this I like to find something I
can point to without a doubt as to the cause of the problem, but I was not truly
comfortable with the injector cup as the solution. Still, I wasn’t ready to
entertain the likelihood of two contributing problems at the same time, and needed
to move forward with the job. Thus I was disappointed that the problem still
existed when the engine was run again, but not completely surprised.
At least
now I could be sure the problem was the head gasket or liner problem, or a
cracked head. At any rate the head needed to come off. Once the head was off,
inspection of the gasket clearly showed an area about 1 1/2
inches long on the #2 cylinder where combustion gas was escaping. The head
gasket has a metal fire ring on each cylinder. The ring sits on top of the
cylinder liner and is compressed when the head is torqued. A ring that has been
sealing properly will have a shiny silver circle all the way around it where it
was in contact with the liner and on the other side, the head surface. A place
that was leaking will have a dull, brown or grey appearance, and you can
usually see a track where the combustion gasses went past the gasket to the
nearest coolant passage. Liner protrusion always needs to be checked in this
case, at the very least on the cylinder that was leaking. A liner with too
little protrusion will not provide enough crush on the fire ring, and it will
fail to hold compression. Other causes can be improperly torqued head bolts or
a warped head.
In this
case the head was flat, liner protrusion was ok, so the engine was reassembled
and now passed the road test. With 20/20
hindsight, I wish I had gone ahead and pulled the head after seeing nothing
absolute with the injector sleeve, but at the same time, one doesn’t want to
waste time and customer money looking for a problem you’re not sure is there. Sometimes
a job just does that to you. Explaining these things to the customer is the
hard part. Many don’t understand that
repair is not always a cut-and-dried, point A to B process.
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