1980 300SD Oil Consumption

Oil consumption has appeared as an issue following the Christmas holidays. During this 2 week period, I drove very little. Following the holidays, I found oil consumption to be high. Initially 1.5 qts in the first 150 miles! Next oil top-off showed consumption down to 1.0 qt in same distance. Currrently, oil consumption has recovered to the historic 1 qt. per 1500 miles. Rear of car has oil mist grunge so I suspect it was going out tailpipe. No new external oil leaks. I suspect valve seals or a turbo seal though turbo boost has remained unchanged (max P and boost response). Comments?

Forums

Diesel Engine Specific Aid

Chassis Model Number

W116

A shot in the dark

Sounds like an anomoly of some sort.. :-). You will have a challenge trying to find the problem if it is not doing it all the time. Sounds like a breather problem. Make sure the breather did not get restricted or collapsed in some way. That is too much oil for valve stem seals to just happen temporarily.

1980 300SD Oil Consumption

Am beginning to suspect the foot valve at the oil drain tube into the oil pan. Noticed oil on outside of drain tube yesterday but not too surprised as I do not have an O-ring seal at the breather downpipe. Any way to successfully check this valve?

I believe I have fixed the

I believe I have fixed the oil consumption problem.
As in previous post, I focused on the crankcase breather assembly and the crankcase foot valve where the captured beather oil actually returns to the oil pan.
I dismantled the breather assembly by bending the retainer tabs and removing the top. Pretty unimpressive and definitely no blockage of any passages. Dropping down to the oil return line itself, as noted before there was no o-ring in the breather side to crankcase side tube joint. Fresh oil deposits were evident around outside of this connection. Nothing unusual was noted at the crancase connection but I suspected the foot valve ( check valve allowing flow one way into the crankcase) might be fouled allowing flow to go back up the tubing.
In operation, the whole set-up is supposed to seperate the bulk of crankcase vent (from valve cover) oil from gases. The oil exits the crankcase breather down the tubing (dipleg) and actually builds a static level above the foot valve until the static pressure overcomes the check valve allowing flow into the crankcase. Additionally, this level of liquid within the tube provides a gas seal which forces crankcase vapors up and out the valve cover vent. In normal operation, this static liquid height actually goes above the o-ring sealed return tube connection.
For a fix, I installed an o-ring into the tube connection. Suspecting the check valve could also be fouled, I drained the crankcase and flushed a quart of Berrymans down the tube, followed by a quart of diesel.
Results? Oil comsumption has dropped to ~ 1 quart/3000 miles. This value has remained constant for the past 10,000 miles. Still have a few other leak points(mainly real main seal) but am satisfied I corrected the excess oil consumption from previous.