My '82 6.2 code "J" has developed a leak. Having trouble finding it. Does not appear to be rear main, or oil pan. Looks like perhaps back of motor up top. Right under, and behind the air cleaner on pass. side there is a large vacuum pot looking thing, that appears to be weeping oil. I cleaned it today, and will check it after driving tomorrow to see if oil has returned. What is that thing, and how difficult to replace if it is the culprit. I have also noticed that oil seems to be blowing up the dipstick(but not out) and the "tuna can" up front is weeping a little oil out the small hole in the top. Do these things indicate a big problem about to blow up on me? How do I head off the problem before gets worse? I bought 3.5 years ago with 127K, now 201K. Never leaked before, now dropping about a quart and a half every ten days. Oil leaks down for about an hour after shutdown, indicating leak occurs only while running. Fuel economy has remained the same as always, 19-20 around town, rarely driven on the highway. Oil pressure same as always, 50-60psi range. Sorry to be long winded, trying to give as much info to solve the problem. Thanks, Tony

The vacuum pump - for heating\ac system, T350 and T400 transmission control - seals are leaking, requires replacement of pump assembly.
GM, NAPA, etc.

The CDR, cap and hoses - similar to PCV, but for Diesels - require servicing\replacement @30k miles.

Dirty intake air filter will cause more oil vapors to be drawn thru functioning CDR system, with resultant dripping.
CDR system can then become clogged up, causing rise in crankcase pressure.

Remove dipstick with engine running, check for pressure in tube - should be none.
If pressurized, remove oil filler cap - pressure should drop, indicating plugged CDR system.

With all CDR system temporarily removed, pressure in crankcase indicates other engine problems - excessive rings wear, cracked piston(s), etc

Compression check 380psi minimum across all cylinders

Thanks very much for the info. Sounds like the CDR is certainly long overdue for a replacement. I'll do the troubleshooting in the morning. Is there a way to eliminate the vacuum pump, as I do not have AC, or an auto tranny? Or is it necessary to operate something else?

The vac pump is part of the oil pump drive - an assy minus the pump is vailable for the vans and the 6.5L series, directly interchangeable.

The pump supplys vacuum for the heater\defroster doors, and the cruise control.