This may sound stupid, but it is honest advice: when working under the hood, watch out for hitting you head on the grill. The hood doesn't raise up far enough for my needs, and I am constantly clobbering myself. You would think I would learn.

My trunk seal got folded over slightly and let in water into the trunk. So make sure your trunk is dry.

If your IP has a small red cap with OEL on it, that means it has its own dedicated oil supply. This oil should be changed when you do a normal oil change. You can find directions elsewhere on peachparts.

The IP works slightly differently than on 123 vehicles and is pneumatically governed (there is a line from the intake manifold, behind the engine, over to the IP). If your idle is unsteady, your necessary adjustments will differ a lot from most of the advice you read here for w123 cars.

Similar to a 123, check your vac lines from the vac pump to the intake and from the vac pump to the brake booster. Make sure they don't contain oil.

My early w115 does not use vacuum for the tranny or to shut off the car. I am not sure if yours is the same. So for me, it is confusing to read all this advice about vacuum adjustments when it wasn't actually relevant to my situation.

Set you watch ahead so you aren't late to any important meetings. Rushing is difficult in a w115.

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).