Cadillac Repair: oil leak/drip, engine oil leaks

Question
'87 Coupe DeVille 4.1L.  Oil leak/drip mostly on LH side, but spot from RH also.  I've learned there is an 0-ring that seals the oil feed pipe to the filter adapter.  I've previously looked for/found/tighten loose fasteners at rear of oil pan, but that did not solve problem.  Oil is being 'blown' back along the bottom of the transmission oil pan and rearwards.  Tried dye, but didn't help.  Is this oil pipe o-ring a common occurrence in LH leaks?  Any tips/advice before I deal with it?  Thank you very much!

Answer
Hi Dave,

     What I do is clean all the engine oil leak areas using brake clean or engine degreaser. That way the only oil seen is whats actually leaking and its trail can be traced to the leak source. Because of the age of the car the leak could be from anywhere. The most common leak source is from the oil cooler lines that bolt to the oil filter adapter housing...but they leak between the line and the fitting and are visable. If the o-ring from the adapter to block is leaking it can come out the bottom down by the torque converter inspection cover. Also the rear crankshaft main seal and rear main bearing cap seal can leak and come out the same spot. It looks like the rear of the oil pan is leaking but its not.

     On the RH side the 2 lower timing cover bolts on each side behind the balancer loosen up and snugging them with a wrench might stop the leak. Otherwise look closely at the front timing cover seal.

     Hopefully something will present itself after cleaning and running the engine. Bill