Jim Grant's Tech Tips
'90 Jeep Cherokee, Oil Loss Through Valve Cover
Q:
I've been losing oil (not burning) in my ‘90 Jeep Cherokee
with a 4.0 liter engine. The very top of the valve cover always has a
lot of oil on it from the rubber grommet type hose connection to the end
of the cover. I ran the engine while looking at the cover and noticed
some oil bubbling around this rubber grommet/plug. I'm assuming that this
is where the PCV valve is located. This rubber connection leads back through
a system of small diameter plastic pipes to the air cleaner. I do see
oil or evidence of oil around this system. I'm suspecting that the oil
is being blown up and out of this rubber plug type connection in the top
of the valve cover and then it just runs down the top of the valve cover
and eventually down to the ground. It is my understanding that there is
a known historical problem with this engine regarding the valve cover
gaskets. But I don't see that the oil is going out of the gasket, as it
looks like it's blowing past this rubber plug/connection. Does this sound
familiar or common? What is the solution? Obviously I could replace this
ventilation system (and PCV valve if that's what it is) but I don't really
want to spend the money for plug and chug mechanics. Nor do I want to
be ripped off by the Chrysler dealer. Can you give me some answers, suggestions
or referrals?
A:
Plug and chug mechanics?
I like that one. You’re problem is a common problem and it is easily
fixed. Your Jeep doesn’t use a PCV valve persay. There are 2 hoses
from the valve cover of your engine. The larger of the 2 travels to the
air cleaner box. The smaller hose/tube which is mainly plastic travels
to a fitting on the intake manifold. The most common problem with this
system is the small plastic tube and/or the fitting on the intake manifold
becoming restricted and plugged with deposits. The fix? replace the plastic
tube and be sure to clean the fitting on the intake manifold. Don’t
waste time trying to clean the plastic tube it just doesn’t happen.
With a little plugging and chugging your Jeep won’t be blowing oil
bubbles any more.
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