Please note: this
is not intended to be a complete "How To", just a brief walkthrough
of our experience
The Inline six 4.0 liter
engine in Jeeps has a tendancy to blow oil into the air filter when
the engine gets old. The first thing to check for is a clogged CCV
gromet and vacuum line. Cherokee America
has a good write up on this in their Tech section, so I won't
discuss that work here. If you have replaced the CCV gromet, you
have a strong vacuum, and your engine is still blowing oil, then
the next step is to remove the valve cover and clean the sludge or
carbon accumulation off the inside. This is not as scary as many
people with limited mechanical experience might think, as there are
no parts requiring adjustment that you will be dealing with. Just
nuts and bolts.
If you do not have any
mechanical experience I recommend you consult with a shop manual
before attempting any work. This work was done on an engine with an
aluminum valve cover. Steel covers should be similar. I have not
seen a plastic cover and cannot vouch for what they look like
inside, but the principles should be the same.
Before Dissasembly
Oil in (2 week old) air filter
The first step is to remove the CCV gromets and
unbolt the valve cover. You may need to remove various other
brackets and lines to remove the cover, depending on your model and
year. A flex driver really helps to reach the back bolts.
Next remove the snorkles and splash guards from
the valve cover. In this case there was not much sludge, but a lot
of carbon.
Rocker arms look good
Inside of valve cover
Snorkle with splash guard on top
Splash guard is coated in carbon
Clean everything! In this case only the valve
cover and snorkles needed cleaning. If you have a lot of sludge you
may need to clean the head as well to clear the oil return lines.
We used varsol and a scraper on the valve cover and snorkles, as
they have no moving parts and are easily wiped down afterwards. We
reused the gaskets from the snorkels (if you destroy them you could
use RTV), but replaced the gasket on the valve cover. The mating
surfaces for the valve cover were cleaned with rubbing alcohol. I
understand that some Jeeps did not have gaskets on the valve cover,
just a bead of RTV. We were told that is was best to put a new
gasket on regardless of whether there was one there before. This
may be different on a plastic valve cover.
Clean, reassembled, valve cover
Back together showing clean splash guards in cover
We used a small bead of RTV on both sides of the
gasket to seal any irregularities. Don't go crazy with the RTV or
it will squeeze out into the rocker arms. The valve cover was
difficult to get back into place correctly. Be sure to wait 24
hours to let RTV cure.
At this point we
have no leaking around the valve cover, after a couple of hard hill
climbs there is no oil in the air filter (yet - cross your
fingers), and there is a significant power increase.
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