Hi guys,
My wife has a 2000 Cherokee 4.0L with 80k miles. For the past month or so I
have been refilling the coolant recovery tank weekly. No leak to be found
anywhere. The oil looked fine, no hot chocolate look. I cleaned the oil
filler cap and replaced it. One week later I examined it and there is a
greenish-yellow sludge on it. It appears water soluble. I'm thinking this is
not good news. How common is this? Not much discussion of bad head gaskets
or cracks with this engine.

The next problem may be related. We have also been experiencing intermittent
check gauge light. The oil pressure at idle dips well below 10 lbs sometimes
under very hot conditions. I have verified this with a mechanical gauge. I
have a 98 TJ, same engine and mileage. In extreme heat, my oil pressure may
hit a low of 10 at idle, but never lower, usually closer to 20 under less
extreme temperatures. The 10lbs doesn't bother me, but the Cherokee dipping
down to 5lbs or lower does bother me. Pressure while driving seems normal.
Now that I discovered possible coolant in the oil, I'm wondering if that is
affecting the idle oil pressure, either due to some frothing or just
clogging the filter. Trade in time? My wife wants something different
anyway. Thanks for any opinions. -Nick