"Zito, James A \(GE Infra, Energy\)" <james.zito@ps.ge.com> wrote:
: Well as I was changing the oil on the Dakota ('03 3.9), I noticed some oil on the breather hose coming out of the air hat. So I popped the hat and looked down the TB it looked "moist," no big puddle but "damp." I tried to snap a couple digital pictures but they didn't come out worth a damn.
: So the question is have I blown the dreaded belly pan? If so what all do I need to buy to replace it? The stinking truck is about 3k past the powertrain warranty.....;-(((((((((((
There's a fairly easy test you can do to check the condition of the
belly pan gasket. I don't know exactly how all the hoses and such on
the GenIII V6 are routed, so rather than tell you which hoses to remove,
block off, etc. I'll just give you the general theory and you can apply it
to your engine. :-)
First how it is supposed to work:
The crankcase of your engine contains vapors due to blowby past
the pistons. If the crankcase were completely sealed off, this would
generate pressure inside which would constantly be trying to blow out
various seals and gaskets (such as the oil pan gasket). The original
solution to the problem was simply to put a breather on one (or both)
of the valve covers, so the vapors could escape into the open air.
Nowadays, a PCV (positive crankcase ventilation) system is used so that
these vapors get sucked into the engine instead, and burned. In this
system, there is a PCV valve on one valve cover, and that is connected
via a tube to the intake manifold. Vacuum from the engine sucks
the vapors from the crankcase through the PCV valve and into the intake
manifold, where they mix with the normal air/fuel stream and are sucked
through the intake valves into the combustion chamber and burned. In
addition to metering the air flow, the PCV valve also serves as a one
way check valve, to prevent an engine backfire from being able to travel
through the PCV tube into the valve cover area and igniting any flammable
fumes which might be in there. On the other valve cover is a tube which
generally connects to the air hat or airbox somewhere. This allows
air to enter the PCV system from the outside if necessary and also
ensures that in the event that there is too much pressure inside the
crankcase for the PCV valve to keep up, the fumes will travel up into
the air filter area and be sucked through the throttle body and burned.
Next, what happens when the belly pan blows:
The bottom of the intake manifold is covered by a "belly pan",
which is sealed by a gasket. If this gasket blows, the vacuum
inside the intake manifold will suck the crankcase vapors directly
into the bottom of the intake manifold. This wouldn't necessarily
be a bad thing since the PCV system is doing the same, however, since
the belly pan is right in the lifter valley area, it also sucks in a good
quantity of engine oil.
How to check for a blown belly pan gasket:
Basically what you want to do is to disable the PCV system so that
it cannot create a vacuum inside of the crankcase, and plug the holes for
the PCV valve and breather so that air cannot enter or leave the crankcase.
When you do that, if the belly pan is not leaking, pressure should build up
inside the crankcase. However, if the belly pan gasket is blown, vacuum
from the intake manifold will create a vacuum inside the crankcase. So,
what you will want to do is to find the tube that runs from one of the valve
covers to your air intake system and pull it out of the grommet in the valve
cover. That's the breather tube. Next, find the PCV valve and pull it out
of its grommet also. (Leave the PCV valve attached to the hose though so
as to not create a large vacuum leak.) Now you want to block off one of
those holes in the valve cover - either have an assistant cover it with
their hand, or perhaps instead of removing the breather hose, if you have
a pair of hose pinch-off pliers, you could just clamp them onto the breather
hose. If you're by yourself you could also block that hole off by leaving
the breather hose attached to the valve cover, but detaching it at the airbox,
then cover it with your thumb or kink the hose and hold it shut with tape
or something, or just stuff a large bolt in the end. Anyway - however you
do it, plug off one of the holes and then start the engine and go to the
remaining hole. Cover it with your hand, or hold a piece of paper or something
over it. Basically what you are doing is checking to see wether it is
trying to suck air into the valve cover or blow it out. If you can't tell,
you might need to block it off for 10-15 seconds so that the pressure or
vacuum can build up to a level where you can determine which it is doing.
If you feel pressure, this is the blowby from the pistons, and is normal. If
you feel vacuum, the belly pan gasket is blown. (Since you have all other
air paths blocked to the crankcase, really the only way a vacuum could form
there is due to air being sucked into the intake manifold past a blown belly
pan gasket.)
Heh! Sorry for the long winded post there, but anyone who bothers to
read to this point will at least be able to check for this no matter
how the PCV system happens to be plumbed. :-) Or maybe it will help
you to win a game of trivial pursuit or something. ;-)
Anyhoo, I hope that helps, let me know if any of the above isn't
clear...
Oh, and as far as what is involved, feel free to check out the
MPI Intake install guide at:
http://www.steigerperformance.com/docs/MPIIntakeManifoldInstallationGuide.pdf
Its not a guide to replacing the belly pan obviously, but should give
you a decent idea of what is involved to R&R an intake manifold on these
engines. Good luck with it!
--
-Jon-
.- Jon Steiger --- jon@dakota-truck.net or jon@jonsteiger.com -.
| 67 Dodge Coronet, 70 Plymouth Barracuda, 76 Peugeot TSA |
| 78 Dodge B100, 90 Dodge Dakota Convertible, 92 Dodge Ram 4x4 |
| 96 Dodge Dakota, 96 Suzuki Intruder 1400, 96 Kolb FireFly |
| 99 Jeep Cherokee 4x4, 01 Dodge Ram 3500 CTD |
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